No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
High Strain Rate Superplasticity in a Friction Stir Processed 7075 Al Alloy
Abstract
In this paper, the authors report the first results using friction stir processing (FSP). In the last ten years, a new technique of Friction Stir Welding (FSW) has emerged as an exciting solid state joining technique for aluminum alloys. This technique, developed by The Welding Institute (TWI), involves traversing a rotating tool that produces intense plastic deformation through a stirring action. The localized heating is produced by friction between the tool shoulder and the sheet top surface, as well as plastic deformation of the material in contact with the tool. This results in a stirred zone with a very fine grain size in a single pass. Mahoney et al. observed a grain size of 3 {micro}m in a 7075 Al alloy. This process can be easily adopted as a processing technique to obtain fine grain size. FSP of a commercial 7075 Al alloy resulted in significant enhancement of superplastic properties. The optimum superplastic strain rate was 10{sup {minus}2}s{sup {minus}1} at 490 C in the FSP 7075 Al alloy, an improvement of more than an order of magnitude in strain rate. The present results suggest an exciting possibility to use a simple FSP technique to enhance grain size dependent properties.
... This innovative design enables the rotating tool not only to facilitate plastic deformation within the chamber but also to generate heat through friction, thereby further enhancing the overall process [5]. Friction stir processing (FSP), developed by Mishra in 1999 [6], operates on the same principles as friction stir welding (FSW) but focuses on modifying the microstructure of specimen surfaces to improve their surface properties without joining samples. All process parameters can be categorized into machine variables, tool design variables, and material properties [7]. ...
... FSP was initially used to enhance the superplastic behavior by creating ultrafine-grained material (UFG) [6,9]. An optimal range of modification process parameters plays an important role in achieving Ultra-Fine Grain (UFG) modification across a diverse variety array of parent metals. ...
FSP is a relatively new technique that changes the microstructure on the surface of the material to improve mechanical properties in the desired zone. This study aimed to investigate the surface quality of AA2098 sheets after being subjected to friction stir processing under different conditions of feed rate and rotational speed. A DoE analysis was developed with two factors, feed rate and rotational speed, and three different levels of 75, 100, 125 mm/min and 1000, 1250, 1500 rpm respectively, in order to assess the processed surface quality. The Sa parameter was used to represent the surface quality in different zones of the process, near entrance tool, middle and near exit tool, and ANOVA analysis was conducted. The results indicated that only the position and feed rate have a statistical influence on surface roughness. Additionally, the surface quality is strongly affected by the position relative to the entrance of the tool and the side (retreating or advancing sides). The roughness was found to be significantly lower on the advancing side rather than on the retreating side.
... FSW results in a strong joint with excellent material properties, which is difficult to achieve in traditional welding techniques. FSP is the modified version of FSW, conceived by Mishra et al. [2] in 1999. FSP functions on the same mechanical principle as FSW, like the identical setup, a non-depleting tool equipped with a shoulder and pin. ...
... It was cleared from the modelling that; the maximum temperature is proportional to the size of the shoulder. The Power (P) required in kW for the process is the direct function of SD in mm and is given by Eq. (2). ...
Friction stir processing (FSP) has gained significant attention worldwide since its inception due to its remarkable solid-state characteristics and microstructure refinement. However, the complex geometry of the FSP and 3-D features makes it challenging to create a set of governing equations for analyzing the post-process theoretical behavior. Due to significant deformation, experiments cannot provide comprehensive information throughout the real process, which frequently entails expense, resources, and time; numerical analysis has been examined extensively over the former to solve these concerns. Numerous alternative processes are to be simulated using FSP’s numerical analysis before physical testing to better understand the impact of various system characteristics. An attempt has been made to explore the latest research on the development of various numerical modelling techniques that lead to meaningful insight to enhance the performance of FSP. An advanced numerical technique for studying the influence of different field variables, changes in tool orientation on material flow coupled with appropriate surface contact involving temperature-dependent coefficient of friction values using advanced smoothed particle hydrodynamics on a GPU hardware configuration is still in future scope. This necessity to develop thermo-mechanical models of surface composites facilitates accurate prediction of the thermal record and particle dispersion in FSP. This article compiles computational approaches, the potential of different FEA software, and other post-processing parameters, viz., heat generation, temperature distribution, and material transition. In this regard, some vital challenges and issues regarding the numerical approaches of friction stir processing remain to be addressed, and opportunities for future research prospects are thus recommended.
... This paved way to the development of copper surface composites wherein hard ceramic particles are dispersed onto copper surface through surface modification techniques, such that a modified composite layer for certain thickness will be developed while properties beneath composite layer remain unchanged. Development of a surface composite layer can be attained through a thermo mechanical processing technique named Friction Stir Processing (FSP) which is a solid state fabrication method and was coined by Mishra et al, [7]. In this fabrication process, a groove will be cut for a defined depth and ceramic particles that have to be dispersed will be compacted into groove. ...
This research deals with investigating the effects of amount of hybrid reinforcement, rotational speed and traverse speed on the mechanical and wear characteristics of copper surface composites fabricated via friction stir processing. Aluminum oxide and boron carbide at 1:1 ratio was dispersed onto copper substrate at various volume fractions (5, 10 and 15 vol. %) at different traverse speed (40, 60 and 80 mm/min) and rotational speed (800, 950 and 1300 rpm). Microstructural characterization of developed copper surface composites dispersed with varying volume fraction of hybrid reinforcement proved reduction in grain size and homogenous distribution of ceramic particles. Results stated that the percentage of particles dispersed, traverse speed and rotational speed have high impact in defining the property of developed copper surface composites. A positive trend in mechanical strength was observed throughout the study. Increase in hybrid reinforcement dispersion and traverse speed increases the microhardness value of developed surface composites while increase in rotational speed leads to reduction in microhardness value.
... 1,2 The FSP method was developed in 1999, based on similar characteristics of FS-Welding (FSW). [3][4][5][6] Earlier FSP was used to produce superplasticity in the material. However with the advancement in the FSP technique, it was used to produce the surface metal matrix composites. ...
Aluminum alloys are known for their extensive use in aerospace, automobile, marine, etc., industries due to their excellent inherent properties. Recent studies have developed different methods to modify the surface properties of aluminum by producing surface composites, such as the friction stir processing (FSP) method. The current study made an effort to develop a new hybrid surface composite of AA5083/(SiC-Gr) using the FSP method. For FSP process optimization, the response surface methodology (RSM) has been used. For creating the mathematical model using RSM, various input process parameters of the FSP are selected to predict the output characteristics of the prepared hybrid composite. A Box-Behnken design was used for the process with four factors, each factor was used with three levels, and the RSM was utilized to form a regression model to predict the responses. The ANOVA analysis suggests that NoP (number of passes): 3 and RV (reinforcement volume): 75:25 (SiC: Gr) ratio are the significant parameters of the study with a p-value less than .05. The novelty of this study lies in the development of a new hybrid surface composite of AA5083/(SiC-Gr) using the friction stir processing (FSP) method, with optimization achieved through the response surface methodology (RSM) and multi-objective selection criteria, resulting in predicted outcomes within a range of ±10% of the experimental observations.
... This process was first proposed by Mishra during the preparation of superplastic 7075 Aluminum alloy. [108] In principle, this process is more similar to the friction stir welding process, where a non-consumable rotating tool at high speeds is used to generate the frictional heat to join plates. [109] The schematic of friction stir processing is shown in Fig. 7(a). ...
Additive manufacturing (AM) technologies revolutionized the manufacturing sector by enabling the production of complex components. But, the poor surface integrity hinders the direct functional application of as-built components and drastically affects the mechanical and tribological performance. In the last decade, researchers employed various post-processing techniques to improve the surface integrity of AM components. Thermal and chemical energy-based post-processes result in thermally destroyed and chemically modified surface layers on the finished surface. In contrast, mechanical energy-based post-processing techniques do not result in any modified finished surface integrities, due to which these techniques were extensively used for post-processing the AM components. The current article focuses on mechanical energy-based severe plastic deformation post-processing techniques to improve the surface integrity of the metal AM components. A detailed review of the published literature specific to each of these processes was carried out, and the research gaps are presented and adequately discussed in this paper.
... Others used SPD methods include groove pressing (CGP) [9,10], equal channel angular pressing (ECAP) [11],friction stir processing and high pressing torsion (HPT) [12], [13], [14].These methods have two major drawbacks. To begin with, the forming machines have large load capacities and are outfitted with expensive dies. ...
The accumulative roll-bonding process (ARB) is one of the severe plastic deformation methods. It aims at producing nano/ultra-fine-grained materials along with enhancements in the mechanical properties. In this work, ARB was performed on commercially cheap and available aluminium alloys in Jordan`s local market; AL-2024-O and AL-1100-Oalloys. Four bonding cycles were applied to promote grain refinement at room temperature with no pre/post heat treatment. In ARB processes, the thickness is reduced by 50% in each pass. A new stacking technique has been performed at the alternate layers depending on the friction of its scratched edges. After the production of samples and the investigation of mechanical properties through micro hardness test, tensile test was accomplished at room temperature after each cycle with the aim of determining whether ARB increases the mechanical properties of both aluminium alloys besides identifying the instance were material experiences high ultimate tensile strength. Information about the texture, microstructure and average crystalline size of the samples was obtained using SEM and XRD. The hardness test shows improvements for AL-2024-O/1100-O for each cycle and reported 125 HV and 80 HV respectively after four rolling cycles. The highest UTS was recorded for AL-2024-O and 1100-O on the 4th pass and reported 370 MPa and 170MPa respectively. It was also found out that the percentage elongation decreased due to a decrease in ductility after undergoing the ARB process. Moreover, after four rolling cycles, the average grain size for AL-2024/1100 decreased to 39.6 nm and 59.9 nm respectively.
... Notable variants of FSW, such as SSFSW [7], Dual Rotation FSW [8], Friction Stir Spot Welding (FSSW), and Refill FSSW [9], have emerged and found extensive applications in various industries. Furthermore, the principle of FSW has been adapted to work on a single plate with different materials, tools, and machine parameters, leading to the development of friction stir processing (FSP) [10,11]. FSP has taken pace in the lightest metal alloys like magnesium [12] and in developing metal matrix mono and hybrid composites [13,14]. ...
This research focuses on the computational modelling and comparative analysis of friction
stir welding (FSW) and stationary shoulder friction stir welding (SSFSW) applied to AA6061-T6
aluminium alloy. SSFSW, an FSW variant, employs a stationary shoulder and a rotating pin. This
study introduces a numerical model for both processes, using the innovative Smoothed Particle
Hydrodynamics (SPH) technique to capture their distinct thermo-mechanical characteristics. The aim
is to unravel its mechanics and multi-physics in SSFSW and compare it with conventional FSW. The
temperatures predicted by the model exhibited a close agreement between the advancing side (AS)
and retreating side (RS). Plastic strain patterns show that regular FSW is different from SSFSW. In
SSFSW, the strain is less, and the plastic area is comparatively slightly narrower. The distinct “ironing
effect” resulting from the stationary shoulder in SSFSW reduces the heat-affected zone (HAZ). Yet, it
maintains efficient plasticisation and material flow within the pin-affected zone (PAZ). This research
emphasises the significant impact of temperature, strain, material flow, and thermo-mechanical
characteristics on the quality of joints. Future suggestions include exploring process parameters more
broadly, examining dissimilar welding techniques and hybrid approaches, and comprehensively
investigating the diverse effects of SSFSW under various configurations and joint angles.
... This was first successfully developed in 1991 by the welding Institute of United Kingdom (UK) [1]. Later on, FSW process gradually modified into FSP and finds application metal processing industries, particularly in the processing of light-weight materials such as aluminium (Al) and magnesium (Mg) alloys [2,3]. The rise of FSP can be attributed to couple of aspects: (i) Microstructural refinement (grain refinement and dynamic recrystallization) by sever plastic deformation (SPD) of materials [4,5], (ii) absence of melting of constituents martials offer better economic aspects [6], (iii) possibilities to fabricate homogeneous surface composite in the presence of reinforcement phases [7,8], (iv) absence of casting defects [9] and many more. ...
This investigation deals with the microstructural and mechanical behaviours of friction stir processed (FSPed) commercially available pure magnesium with different tool profile geometry. The micro-level properties were assessed through in-situ micro-pillar compression which showed that FSPed material experienced significant plastic deformation and even re-distribution of residual oxide particles which was present in the cast magnesium together with grain refinement (from 3.4 μm to 2.6–2.7 μm). These changes in microstructure contributed to raise the compressive and yield strengths of the FSPed magnesium, up to 99 MPa and 94 MPa respectively, compared to 33 MPa of cast magnesium, when triangular tool profile was employed. Furthermore, the deformed material acquires ductile breakage with improved plasticity (micro-necking) irrespective of processing conditions, that is, either cast or friction stir processed.
... In recent years, the solid-state friction stir processing method has been introduced by Mishra [3], primarily aimed at producing surface composites. Friction stir processing is a method based on friction stir welding [4]. In this process, similar to friction stir welding, two tools, namely a pinless tool and a pinned tool, are used. ...
This study examines how friction stir processing parameters affect the properties of AA6061/Al2O3 nanocomposites. The tool geometry is one of the key factors in this process, which affects the contact area between the tool and the workpiece, as well as the resulting heat generated by rotational speed, traverse speed, dwell time, and tool tilt. Tools with conical geometry exhibit pulsating mixing behavior, where a higher pulse production results in smaller particle size, more uniform distribution of reinforcing particles within the metallic matrix, and consequently, improved tensile strength and hardness. Based on experimental studies and extensive trial and error, it has been established that square tools generate a higher number of pulses, leading to the attainment of superior mechanical properties for aluminum alloys. Therefore, in this research, the conical tool geometry with sample number 4 was chosen.
... Friction stir processing (FSP) is a novel materials processing technique which is developed in the late 1990s by Mishra and his colleagues [3] based on the principles of friction stir welding (FSW). It involves the use of a specially designed rotating tool which inserted into the workpiece and moves across a predefined path on the workpiece surface. ...
... A solid state technique such as Friction Stir Processing (FSP) is the best suited to avoid reaction between reinforcement particle and metal matrix and to maintain the elemental state of the metallic particle [4]. FSP was invented and evolved by Mishra et al. [9], which works on the principle of Friction Stir Welding (FSW). FSW is a revolutionary solid state joining process, invented and patented by the Welding Institute, UK in the year 1991 (G.B. ...
... One of the most commonly used materials for structural applications in the abovementioned industrial sectors is aluminum and its alloys due to its superior formability, high specific strength, and corrosion resistance [8]. The FSP method was investigated by Mishra et al. [9] in order to achieve high strain rate superplasticity in AA7075. The results show that FSP can achieve optimum superplasticity at 1 × 10 −2 s −1 and 490 °C. ...
The present study investigated the effect of hydrogen on the mechanical degradation of friction stir processed (FSPed) 5083 aluminum alloy by intense hydrogen cathodic charging (HCC). The effect of different numbers of FSP passes was investigated: 3 and 8 passes, respectively. Hydrogen-charged and uncharged specimens were subjected to tensile testing and microhardness evaluation analysis, and were examined through optical microscopy, focus variation microscopy (FVM), and scanning electron microscopy (SEM) both on the microstructure and fracture zone. The results showed that the FSP process introduced a refined microstructure with finer grains. This led to an improved mechanical response during tension tests of the uncharged specimens; the energy absorption increased from 85 MJ/m 3 of the base material to 94 MJ/m 3 and 97 MJ/m 3 for the 3 and 8 FSP passes, respectively. The introduction of hydrogen through the HCC process led to a more brittle mechanical response with a decrease in the energy absorption capability for all the charged specimens. The more prone specimen was the 8 FSP passes specimen where the energy absorption dropped by 20% and 71% for the two different charging current densities. The 3 FSP passes specimen presented a reduction of energy absorption of 4% and 18%, respectively, where the base material presented a reduction of 8% and 14%, respectively. This brittle response is also evident from the microhardness testing where the hydrogen charging led to increased surface hardness values. The 3 FSP passes specimen presented a better mechanical response with respect to the base material specimen (and the 8 FSP passes specimen) for all the charging conditions, and this led to the conclusion that a small number FSP surface modification could be a beneficial surface modification process as it improves the mechanical response of the material and is not significantly affected by hydrogen charging environments.
... Therefore, different mechanical properties will be obtained under different strain conditions. Friction stir processing (FSP) was improved by R.S. Mishra et al. [8] and is based on friction stir welding (FSW). Its principle is the same as that of FSW. ...
An inhomogeneous microstructure induced by high rotating speed submerged friction stir processing (HRS-SFSP) on 6061 aluminum alloy was researched in detail.The microstructures of the aluminum alloy processing zone were characterized by electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) qualitatively and quantitatively.The results show that the recrystallization proportion in the inhomogeneous structure of the processing zone is 14.3%, 37.8% and 35.9%, respectively. Different degrees of grain deformation can affect the dislocation and lead to the formation of a plastic–elastic interface. At the same time, the second-phase particles in the processing zone were inhomogeneity and relatively, which further promotes the plastic–elastic interface effect. The plastic–elastic interface can significantly improve the strength of aluminum alloy, whileat the same time, rely on recrystallized grains to provide enough plasticity. When the rotation speed was 3600 r/min, the strength and ductility of the aluminum alloy after HRS-SFSP were increased by 48.7% and 10.2% respectively compared with that of BM. In all, the plastic–elastic interface can be formed by using high rotating speed submerged friction stir processing, and the strength-ductility synergy of aluminum alloy can be realized at the plastic–elastic interface.
... The dynamic recrystallization that occurred during FSP, because of the heat caused through friction together with severe plastic deformity is responsible for fine and equiaxed grains produced in the Al matrix [37]. During re-recrystallization, modification of the alloy's microstructure occurs resulting in strengthening its mechanical properties [38]. The elongation to fracture has increased from 17.5% to 20.5% for TIG-welded specimens reflecting an increased ductility. ...
The friction stir processing method was engaged on fusion welded AA5083-F/ER5356 and AA5083-F/ER5356+Sc joints to explore the impact of the process parameters on the mechanical and metallurgical characteristics of the processed weldments. The FSP approach was applied to the TIG-welded joints with pin-less FSP tool. Optical and SEM evaluation was conducted to examine the microstructure of the welds and mechanical analysis such as impact toughness, tensile, microhardness and fractography was performed to evaluate the strength of the weld. The microstructural study of the FSP joints revealed an average grain size of 4 µm for TIG welds and an average of 2 µm for the Sc added TIG weld, when compared to TIG-welded joints, which had an average grain size range of 12 µm and 8 µm for Sc added. All FSPed joints revealed a significant increase in grain refinement. There was a slight improvement in the impact resistance in FSPed samples than TIG welded samples. The FSPed joints' ultimate tensile strength (UTS), which is higher than the tensile strength of the base metal, was 288 MPa for the FSPed joints and 331 MPa with Sc added. The FSP joint's elongation range was decreased to 7.1% but improved for Sc added FSP joints up to 20.5%. The maximum hardness of FSPed TIG-welded joints was 90 HV1, while the maximum hardness of Sc added FSP joints was 95 HV1, which is significantly higher than the maximum hardness of TIG weldments. According to the fractography results, the majority of failure modes are ductile. Therefore, adopting FSP over TIG welding had enhanced the properties of the weld both mechanically and metallurgically.
... Friction Stir Processing (FSP) is an evolving technique to produce surface composite and achieve super plasticity [1]. It was developed in 1999 by Mishra et al. [2]. In FSP, a tool with a rotating speed is introduced into the material which contains the reinforcement particles, and then a traverse speed is provided to the tool. ...
Aluminum alloys are among the most widely used material in the manufacturing industries due to their high strength and lightweight properties. To enhance its surface properties, Friction Stir Processing (FSP) proved itself as an efficient method to enhance its microstructural, mechanical, and tribological properties. However, FSP has many process parameters that can affect the final properties of the material. Therefore, an optimized process parameter is required before the use of FSP to obtain the best results. In this paper, a mathematical model has been developed using Response Surface Methodology to predict the hardness of produced surface composite of AA5083 aluminum alloy by using SiC-Gr hybrid reinforcement. FSP was optimized for its hardness (HRB) property by optimizing the FSP process parameters like Tool rotating speed, Tool Traverse speed, number of FSP passes, and the ratio of hybrid reinforcement volume fraction. It was found that the Tool Rotating speed of 1000 rpm, traverse speed of 80 mm/min, 3 number of FSP passes, and Hybrid reinforcement ratio of 75:25 (SiC:Gr) produced the best result with the hardness of 32.6HRB.
... Due to the drawbacks of the aforementioned methodologies, it is now more important than ever to identify a reliable replacement strategy for the synthesis of MMCs. In order to create superplasticity in the AA7075 alloy, R.S. Mishra and colleagues developed the FSP process in 1999 [16]. Recently, FSP has become a more adaptable practice for producing surface composites. ...
High specific strength and superior corrosion resistance are two key characteristics of the aerospace grade AA7075-T6 alloy. However, the surface behavior of AA7075-T6 is found to be deprived, because of its behavior of being prone to fretting fatigue and adhesive wear under dry sliding conditions. Thus, surface wear behavior improvement with the retention of the microhardness of the alloy is required for increasing its wider application. For this, surface isomorphous precipitates and the soft matrix need to be protected through dispersion of hard thermally stable ceramic SiC with solid-lubricant graphite particles. The dispersion through friction stir processing (FSP) avoids detrimental phase formations by processing the metal alloy below its melting point temperature. Thus, dispersion of SiC-Graphite inside the AA7075-T6 using FSP is the focal point of the study. The low and high wear rate samples have been analyzed using SEM imaging and elemental analysis through XRD and EDS mapping. In this study, reinforcing the SiC-Gr particles greatly improved the wear behavior of the AA7075 alloy. Wear resistance has been controlled by combining soft solid lubricant Gr particles with load-bearing hard SiC nanoparticles. In dry sliding action, the base alloy matrix was severely exposed to wear, but the hard SiC nanoparticles served as load-bearing asperities and improved the wear resistance. Simultaneously, the graphite layers generated the soft solid lubricating tribofilm further to reduce the wear and friction between mating surfaces. The wear mechanisms have changed prominently from adhesion to abrasion and delamination through reinforcing the SiC-Gr reinforcements. The graphite content in a hybrid ratio with SiC hard particles was found to have improved the wear resistance by 78%. The tendency of fatigue was more effectively improved in surface composites as compared to the base alloy
... The method of modifying the surface layer by friction stir processing (FSP) was developed by Mishra et al. [1] based on the basic principles of friction stir welding technology [2,3]. However, FSP, unlike friction stir welding (FSW), is used to modify the microstructure in the surface layer of the product, and not to connect metal elements. ...
The paper presents the results of experimental investigations of the heat generation and microstructure evolution during the friction stir processing (FSP) of the SnSb11Cu6 alloy. The Triflute tool was used for modification; the process was carried out using two rotational speeds of the tool: 280 and 560 RPM and a constant linear speed of 355 mm/min. Microstructure studies were performed employing the techniques of light microscopy and scanning electron microscopy along with analysis of the chemical composition of micro-areas. Additionally, the phase composition was investigated by means of the X-ray diffraction method, and electron backscatter diffraction (EBSD) analysis and hardness testing were performed before and after FSP modification. Furthermore, measurements of the temperature directly on the modified surface by means of a thermal imaging camera and the temperature in the modified zone with a thermocouple system were performed. It was proved that using FSP to modify the SnSbCu alloy promotes refinement and homogenization of the microstructure, as well as improvement of the hardness. The hardness of the starting material was 24 HB, and after FSP, the hardness increased and amounted to, respectively, 25 and 27 HB after processing at 280 and 560 RPM. The microstructure in the stir zone is formed by the dynamic recrystallization (DRX) process and consists of almost equiaxed tin-rich matrix grains with a size of approx. 5–30 µm and fine particles of Cu6Sn5 and SnSb phases. The temperature distribution in the FSP zone is not uniform and changes in a gradient manner.
Friction stir processing (FSP) was applied to incorporate nano-hydroxyapatite (nHA) into magnesium alloy ZM21, resulting in a nano-composite with very small grain size. Addition of nHA particles enhances biomineralization and delay magnesium degradation, and grain refinement through FSP. At stir zones of FSP ZM21 and FSP ZM21-nHA composite, grain size decreased from 56 to 20 µm. The small grain structure of the ZM21-nHA composite was found to increase wettability in studies that included a 72-h immersion in super-saturated simulated body fluid (SBF 5×). The nHA particles also stimulated heterogeneous nucleation, which promoted the rapid initiation and expansion of the calcium phosphate mineral phase. In addition, nHA particles served as nucleation sites, leading to the composite’s quick biomineralization. After 72 h of immersion, the FSP ZM21 and FSP ZM21-nHA composite improved biomineralization, reducing the degradation caused by localized pitting.
The current work takes the benefit of utilizing a composite approach by reinforcing Mg with Zn, Cerium oxide - a rare earth and bone-friendly ceramic, and bioactive hydroxyapatite to develop magnesium-based MMCs for high structural integrity and low degradation inside the human body via stir casting technique in a protective Ar-SF6 environment. The friction stir processing (FSP) technique was employed to tailor the properties of as-cast Mg composites, resulting in further grain refinement and better dispersion of reinforced materials. Phase and microstructure analysis were analyzed via XRD, FESEM, and optical microscopy. During tensile tests, as-cast Mg-5Zn-1HA-1.5CeO2 improved 68.6% in yield strength and 16.3% in ultimate tensile strength. After FSP, the same composite resulted in an overall improvement of 114.6% in yield strength and 31.9% in ultimate strength compared to as-cast pure Mg. Dispersion of inert bioceramics within the Mg matrix results in higher polarization resistance as per Electrochemical impedance spectroscopy (EIS). At the same time, a remarkable 81.6% reduction in H2 emission and an 84.4% decrement in corrosion rate were found during the immersion study for Mg-5Zn-1HA-1.5CeO2 composites. All Mg-based composites exhibited no cytotoxicity as cell viability evaluated via MTT assay was found to be greater than 80% for 50% and 25% extract concentrations. The composite’s hemolysis rate was below 5%, indicating acceptable hemocompatibility. This work provides insight into developing rare earth oxide-incorporated Mg composites with better mechanical capabilities and degradation resistance while avoiding the long-term cytotoxicity of rare-earth materials.
Using solid-state friction stir processing (FSP), an effort has been made in the current research work to produce copper metal matrix composite (Cu-MMC) reinforced with TiB2 particles. It is exposed that the TiB2 particles are evenly distributed throughout the Cu-MMC. Cu-MMC's tensile characteristics, impact strength, and microstructure are evaluated in relation to process parameters such percentage of volume (2%, 4%, and 6%), rotational speed of tool (900, 1200, and 1400 rpm), and traverse speed of tool (15, 20, and 25 mm/min). Experiments are planned and conducted using the Taguchi (L9) orthogonal array (OA) layout on Cu-MMC. Taguchi optimization technique was employed for maximizing the mechanical properties of Cu-MMC. The optimal conditions (i.e., A3B1C2) of 900 rpm, 6 volume percentage of TiB2, and traverse speed at 20 mm/min were used to obtain the best microhardness value. The tensile properties at the optimal conditions (i.e., A1B2C3) are a lesser amount of than those of the base material because of the presence of TiB2 particles that make the matrix brittle. Enhancing the hardness of Cu alloys for use in sliding electrical contacts is of vital significance. Finally, there is a link between Cu-TiB2's microstructure and the mechanical qualities that have been observed.
In recent past, a significant research attention has been given to the study of nanosize ceramic particles reinforced aluminium alloy composites due to its excellent mechanical and surface properties compared to unreinforced counterpart. Hence, the major aim of the present study is to investigate the effects of cryocooling friction stir processing (cryo-FSP) on microstructural evolution, and its effects on mechanical properties & corrosion behavior of a stir-cast 2 wt% nanosize SiC (n-SiC) particles reinforced AA5083 nanocomposite in comparison to the room temperature (RT) FSPed and as cast counterparts. The cryo-FSP was performed successfully using optimized process parameters of 1400 rpm and 40 mm/min traverse speed using a specially designed cryo-FSP setup extracting deformation heat efficiently by a flowing mixture of LN2 and methanol (−30 °C). Evolution of a finer equiaxed grain structure (∼2 μm) with a homogeneous distribution of n-SiC particles and precipitate phases is confirmed (through SEM-EBSD and STEM/TEM analysis) in the cryo-FSPed composite compared to RT-FSPed sample (∼4 μm). The cryo-FSPed sample exhibited a superior yield strength (i.e., YS = 230 ± 3 MPa) compared to the RT-FSPed sample (i.e., YS = 197 ± 4 MPa) with a reasonably good ductility for both (i.e., 14 %). The improved YS is attributed mainly to the grain boundary strengthening due to extra grain refinement induced by cryo-FSP and dispersion strengthening via second phase particles. Different strengthening mechanisms' analyses established a good correlation between the theoretical YS and experimentally obtained tensile YS. Fractography analysis corroborated well with the tensile properties of the corresponding samples. Compared to the interdendritic cast structure, both the FSPed samples exhibited a superior corrosion resistance due to an improved surface characteristic developed in the dynamically recrystallized matrix with uniform dispersion of second phase particles. However, due to more grain boundary active phenomenon and higher misorientation angles, a bit higher corrosion rate could be observed in the fine-grained cryo-FSPed sample compared to the RT-FSPed composite.
Copper matrix composite reinforced with SiC exhibits high electrical and thermal conductivity, as well as superior mechanical properties, making it a potential candidate for thermal management applications. There has been rapid progress in the understanding of Cu-SiC metal matrix composites during the past decade. To accomplish this, powder metallurgy, casting, selective laser melting, composite electroforming technology, and electrodeposition methods have been employed. The optimum cutting conditions for fabrication of Cu-SiC metal matrix composites are still being explored. In recent years, friction stir processing (FSP) has become increasingly popular in the fabrication of composites. FSP is capable of microstructural engineering in Cu-SiC systems. In light of the fact that the electrical/thermal conductivity and mechanical performance of Cu-SiC composites depend on microstructural characteristics such as SiC distribution, grain size, grain orientation, density of dislocations, and bulk density, it seems important to study the effect of manufacturing conditions on microstructure in detail. In this study, the influence of FSP parameters such as rotational and traversal speeds, the number of FSP passes, and the pin profile as well as the characteristics of SiC powder are discussed in detail with regard to macro- and microstructure, hardness, strength, tribological, and electrical properties of FSPed Cu-SiC composites.
The limitations of traditional metallic biomaterials motivated the development of polymer matrix composites to fabricate various biomedical implants. The wear resistance of the composites can be enhanced by modifying the surface properties, using a surface modification process to increase the components’ lifespan. Friction stir processing (FSP) is one of the best solid-state processing techniques for fabricating polymer composites. In the present study, a new, shoulderless tool has been developed to perform FSP to understand the process parameters’ influence to produce an effective processing zone. It may be called ‘Shoulderless Friction Stir Processing’. Therefore, for this research work, the tool rotational speeds of 500, 600 and 700 rpm and traverse speeds of 10, 15 and 20 mm/min have been selected as the process parameters to conduct the FSP on the developed basalt fibre-reinforced polylactic acid composite materials. The obtained result reveals that the tool rotational speed is the most influencing processing parameter, as it affects the surface of the composite. A high rotational speed leads to a high material removal rate, whereas a low rotational speed leads to the burning of the polymer. In addition, the specific wear rate (SWR) is also found to be minimal for the specimen processed at 600 rpm with 20 mm/min traverse speed compared to the other processing parameters.
Due to the challenging issues like high heat generation concerned with hardened steel machining, therefore cutting fluid has been used for removing the more higher cutting temperature. Furthermore, use of nanolubrication system makes the cutting environment more sustainable. The present work represents the impacts of cutting parameters such as cutting speed, feed rate, depth of cut and LRT 30 mineral oil-based ZrO2 nanofluid concentrations in hard turning of AISI D2 steel. The ZrO2 nanofluid was first time implemented for cooling purpose in hard turning application. The performance was examined by taking average surface roughness, tool flank wear, cutting power and cutting temperature results. Experimental results found that the 0.20% nanofluid concentration was the better choice among all adopted weight concentrations (0.05%, 0.2% and 0.5%) of nanofluid. Abrasion, cutting edge chipping and adhesion were found to be the principal wear mode. Also, acceptable range of surface roughness (0.498–0.665 micron) was seen in the entire investigations.KeywordsHard turningZrO2CVDNanofluidCutting power
Friction Stir Processing (FSP) is a well-established solid-state severe plastic deformation surface alteration procedure. Fabrication, processing, and synthesis of materials with just surface alterations are all parts of FSP. As a result, the metal's base characteristics are preserved, and the result is a surface composite. FSP has lately been popular for producing surface composites that improve the tribological, mechanical, and microstructural properties of certain metals. Alloys of aluminum are used widely due to their light weightiness and corrosion resistance. AA2014 is used in the aircraft and automotive industries for its good machinability properties and good strength-to-weight ratio. In the current experiment, FSP was employed to produce a surface composite of AA2014 by using hybrid nano-sized SiC-CNT reinforcement. The number of passes has an important impact in determining the qualities of the surface composite in FSP. This paper examines the effect of the number of passes while keeping rotational and traversal speeds constant during FSP. After the experiment, analysis was carried out for microhardness and tribolog-ical properties. One-, two-, and three-pass FSPs were used to process the AA2014. The properties of the base metal, one-pass, two-pass, and three-pass Friction Stir Processed (FSPed) specimens were studied and compared by performing the experiment three times. From the average results of conducted experiments, it can be deduced that by increasing the number of passes, the microstructure improves in addition to improved coefficient of friction (COF), microhardness, and wear resistance for prepared specimens.
Magnesium (Mg) composites reinforced with carbon-based nanomaterial (CBN) often exhibit low density, enhanced strength, good conductivity, improved wear resistance, and excellent biocompatibility when compared to current industry Mg alloys. This review aims to critically evaluate recent developments in Mg-CBN composites and is divided into five sections: First, a brief introduction to Mg-CBN composites is provided, followed by a discussion of different fabrication techniques for these composites, including powder metallurgy, casting, friction stir processing, and selective laser melting. A particular focus is on the current processing challenges, including dispersion strategies to create homogeneous Mg-CBN composites. The effect of processing on the quantifying disorder in CBNs and distinguishing different sp2 carbon materials is also highlighted. Then, the effect of CBN on various properties of Mg-CBN composites is thoroughly analyzed, and the strengthening efficiency of CNTs and graphene in the Mg matrix is examined. Finally, the potential applications of Mg-CBN composites in various industries are proposed, followed by a summary and suggestions for future research directions in the field of Mg-CBN composites.
In the present research, friction stir processed (FSPed) nano-hydroxyapatite reinforced AZ91D magnesium matrix surface composite has been developed with improved ultimate tensile strength (UTS) and biological performance, which are needed for the bio-implants. Nano-hydroxyapatite reinforcement with varying proportions (5.8%, 8.3%, and 12.5%) was introduced into the AZ91-D parent material (PM) by the grooving method with different grooves of 0.5, 1 & 1.5 mm of width and 2 mm depth machined on the surface of the PM. Taguchi's L-9 orthogonal array was employed to optimize the processing variables for enhancing the UTS of the developed composite material. The optimum parameters were discovered to be the tool rotational speed of 1000 rpm, transverse speed of 50 mm/min, and 12.5% reinforcement concentration. The results revealed that the tool rotational speed contributes the highest effect (43.69%) on UTS, followed by the reinforcement percentage (37.49%) and transverse speed (18.31%). The FSPed samples at the optimized parameter setting confirmed the enhancement of 30.17% and 31.86% in UTS and micro-hardness, respectively, compared to the PM. Cytotoxicity of the optimized sample was also found superior compared to the other FSPed samples. The optimized FSPed composite's grain size was 6.88 times smaller than the AZ91D parent matrix material. The improved mechanical and biological performances of the composites are attributed to the significant grain refinement and proper dispersion of the nHAp reinforcement in the matrix.
Magnesium metal matrix composites (MMMCs) have exceptional mechanical and metallurgical characteristics, which have drawn the interest of researchers across the world. In the present research study, an attempt has been made to fabricate WE43 magnesium (Mg) based nanocomposites using friction stir processing (FSP) after incorporating nano-titanium carbide (TiC) as a reinforcement. Further, the impact of different FSP variables such as transverse speeds (40 mm/min and 80 mm/min), and tool rotation speeds (900 rpm and 1800 rpm) over the metallurgical, wear, and mechanical performance has been studied. The large thermal energy generated by the rotating FSP tool gives rise to the mechanism of dynamic recrystallization and plastic deformation. This contributes to refining the microstructure and improvement in microhardness as per Hall–Patch relation—contributing to prominent grain size refinement and Orowan mechanism strengthening, due to the dispersion of reinforcement particulates. The outcome of the results depicts that the nanocomposite fabricated at a tool rotation speed of 1800 rpm and 80 mm/min transverse shows better mechanical and tribological characteristics than other developed composites and the base alloy. More specifically, the grain size was reduced nearly 12 times, microhardness was 2.58 times higher, and ultimate tensile strength (UTS) was 2.08 times higher when contrasted to the base alloy. Moreover, the unprocessed base material was characterized by an adhesive wear mechanism whereas the presence of scratches depicts the abrasive wear mechanism was dominant for WE43/TiC nanocomposite.
In the present work, the different volume ratios of silicon carbide and titanium dioxide particles were incorporated with AA7075-T651 to improve the surface properties using multipass friction stir processing. The metallurgical study of the friction stir processed samples was examined through optical microscopy and field emission scanning electron microscopy with energy-dispersive X-ray analysis. In addition, the microhardness, wear, and corrosion properties were measured and analyzed. The results revealed that the increased amount of SiC particles caused uniform particle dispersion and was devoid of cluster-rich regions within the matrix. The increased volume of SiC particles exhibited a smaller grain size due to higher grain refinement. The sample with 100% SiC showed superior mechanical, tribological, and corrosion properties. The microhardness of sample with 100% SiC was increased by 13.60% compared to base metal, it was also better compared to other composite samples. Similarly, the coefficient of friction, wear rate, and corrosion resistance properties were reduced by 43.24%, 14.98%, and 75%, respectively.
Friction stir processing (FSP) is used to eliminate the defects and modify the microstructure of the joints made using other welding and joining processes. In transient liquid phase (TLP) bonding, the formation of deleterious phases in the bonding zone as well as diffusion affected zone (DAZ) is always challenging. In this study, FSP was applied as a post-bond treatment to modify the microstructure of TLP joints for 304 stainless steel. Microstructural analysis of the joint after FSP showed no sign of the TLP bond line previously visible in the stir zone as well as refined microstructure due to dynamic recrystallization. The eutectic phases, produced by incomplete isothermal solidification of the liquid interlayer during TLP bonding, were coarse and interconnected before FSP. After FSP, these phases became completely distributed in the stir zone, and in the thermo-mechanically affected zone, they were finer and disconnected from each other. In the thermo-mechanically affected zone, a narrow curved shape TLP bonding line was observed, and its width increased into the heat-affected zone. FSP increased the TLP joint strength by about 37% from the pre-FSP state. After FSP, the joint strength reached about 87% of that of the base metal, which is consistent with the microstructural observations showing a lack of defects and discontinuities at the TLP bond line. As a consequence, FSP can be regarded as a complementary process to improve the quality of TLP joints, maximizing their mechanical properties.
In the recent work, tool shoulder designs such as flat shoulder (TFS), kurl shoulder (TKS), scroll shoulder (TSS), and knurling (TKNS) were creatively designed to improve the surface properties. The AA7075/SiC/Graphene hybrid surface composites were fabricated through friction stir processing using different shoulder designs. The influence of shoulder designs on microstructure, mechanical, tribological, and corrosion properties were examined. The material characterizations such as macrostructure, microstructure, particle dispersion, and elemental analysis were studied through optical microscopy and field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. The current study found that the dispersion of SiC and graphene particles inside the matrix fabricated by the TSS tool design was more uniform due to the tool shoulder feature, leading to improved material flow during stirring. The sample fabricated using the TSS tool displayed higher grain refinement, the smallest grain size, which was 3.5 μm. The TSS design effectively eliminated the cluster formation and obtained a defect-free composite resulting in greater hardness (197 HV), lower wear resistance (0.0038 mm³/m) and higher corrosion resistance (– 0.650 mV) compared to other tool designs. However, the lowest values of hardness, wear rate, and corrosion resistance were obtained by TFS design.
Owing to its excellent properties, Metal Matrix Composites (MMC) has gained popularity and finds application in aerospace, aircraft, shipbuilding, biomedical, biodegradable implant materials and many more. To serve the industrial needs, the manufactured MMC should have homogenous distribution along with minimum agglomeration of reinforcement particles, defect-free microstructure, superior mechanical, tribological and corrosive properties. The techniques implemented to manufacture MMC highly dominate the aforementioned characteristics. According to the physical state of the matrix, the techniques implemented for manufacturing MMC can be classified under two categories i.e. solid state processing and liquid state process. The present article attempts to review the current status of different manufacturing techniques covered under these two categories. The article elaborates on the working principles of state-of-the-art manufacturing techniques, the effect of dominating process parameters and the resulting characteristic of composites. Apart from this, the article does provide data regarding the range of dominating process parameters and resulting mechanical properties of different grades of manufactured MMC. Using this data along with the comparative study, various industries and academicians will be able to select the appropriate techniques for manufacturing MMC.
This work reports a study of friction stir processing (FSP) using different tool designs and altering the pass strategy for two process parameter combinations to locally modify the microstructure and create a defect-free processing zone. FSP is applied on high-pressure die-cast (HPDC) A380 alloy, which is widely used in the die casting sector for automotive and aerospace applications. Gas and shrinkage porosity, brittle, needle-shaped Fe-containing β-FeSiAl5 intermetallic compounds, Al dendrites, coarse and acicular silicon particles, and large second-phase particulates diminish the uniformity of tensile properties across the thickness of an HPDC plate. FSP can eliminate porosity, refine microstructure, and improve tensile properties. An FSP tool design and a pass strategy are identified for the best microstructure consolidation and uniform, enhanced tensile properties. This study underscores the importance of tool features such as scroll design and flats on tool pins and multiple pass-orientation strategies to optimize defect-free, refined microstructure and uniform tensile strength and ductility across the processing zones of HPDC Al alloys.
This study applied friction stir processing (FSP) to the TIG weldments of AA6082-T651 and AA8011-H14 with a single and double V-joint to analyze the FSP technique's impact on the TIG weldments' tensile characteristics. The single V-groove TIG (TIG SV) welded joint was more porous than the double V-groove (TIG DV) one; however, both joints exhibited a coarse-grained microstructure. When FSP was applied to the TIG weldments, the coarse grain structure (grain size 32.05 µm) was transformed into a refined grain structure (grain size 6.68 µm), thereby eradicating the defects that had been seen before FSP. Regardless of the TIG welding groove, FSP enhanced the flexural and tensile properties of the TIG welded joints. Similarly, the hardness was found to have improved due to FSP. However, when comparing the TIG SV + FSP joint properties to those of the TIG DV + FSP joints, it was observed that the TIG DV + FSP joints showed more improved properties. This behavior was correlated with the microstructural grains obtained. The maximum tensile strength of 95.3 MPa was observed for TIG DV + FSP, while the minimum tensile strength (56.1 MPa) was found in the TIG SV joint. The TIG DV welded joint showed a hardness higher by 13.44% compared to that of the TIG SV welded joint, while the TIG DV + FSP joint had a hardness higher by 21.24% than the TIG SV + FSP joint.
In this study, friction stir spot welded joints of Al6061-T6 were obtained using silicon carbide particles as reinforcement. The effect of reinforced particles along with process parameters was analyzed in terms of tensile-shear strength, weld structure, and hook formation. The investigations revealed that tensile-shear strength increased by 29.78% with incorporation of silicon carbide particles in the weld region. The guiding hole diameter was found to be a significant parameter for improved weld strength. Optimal levels of tool rotation speed, pre-dwelling time, and guiding hole diameter were observed as effective process parameters for better weld quality. Weld cross sections were studied under a stereo zoom microscope and an optical microscope to observe different bonding regions. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the presence of silicon carbide particles in the weld region.
The practical applications of magnesium (Mg) alloys are usually beset by their relatively low strength and limited ductility. Herein we attempt to fabricate hexagonal BN nanoplatelet (BNNP) reinforced ZK61 magnesium composites using a combination of spark plasma sintering and friction stir processing. The resulting composites exhibit microstructural characteristics of homogeneous dispersion of BNNP in Mg matrix with refined equiaxed grains and (0002) basal texture roughly surrounding the pin column surface. Transmission electron microscopy observation illustrates that trace amounts of Mg3N2 and MgB2 form at BNNP-Mg interface, in which Mg3N2 locates at the basal plane of a BNNP and MgB2 grows at its open edge. The spatial distribution of Mg3N2 and MgB2 facilitates interfacial wetting and stronger BNNP-Mg interface in such a way that interfacial products act as anchors bonding between them. In comparison with monolithic ZK61 alloy, the BNNP/ZK61 composites display simultaneous improvements in yield strength, hardness and ductility, achieving good strength-ductility balance. This research is expected to shed some light on BNNP potentials for designing and producing magnesium composites with high strength and good ductility.
In this paper, the wear resistance and microhardness of the hybrid and mono surface composite
with Al–Mg–Mn alloy (AA5083) as the matrix material and SiC, Al2O3, Gr, and CNT as the reinforcement
material was investigated experimentally. The surface composite was fabricated by friction stir processing
(FSP). The microstructure of the prepared specimens was observed using optical microscopy. Mono reinforced
surface composite and hybrid reinforced surface composite were tested for their microhardness and
wear resistance before and after FSP and the results were compared. The surface composites showed uniform
dispersion and finer grain size after FSP in comparison with the as-received AA5083. FSP aided the hybrid
reinforced surface composite to increase the maximum microhardness value to 107.5 HV in SiC/Gr reinforcement
as compared to the 89.11 HV in mono Gr reinforced surface composite and 75.15 HV in as-received
AA5083. The hybrid surface composite also provided enhanced wear resistance in comparison with the mono
reinforced surface composite and the base material.
The TIG-welded specimens were friction stir processed (FSPed) to analyze the impact material positioning of the base metals AA8011 and AA6082. The tests included the energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction, microstructure, hardness, tensile test and fracture surface analysis. The mean grain size of 24.83 µm was obtained for the TIG welded joint, 8.68 µm for the FSPed joint with AA6082 alloy on the advancing side (A.S), while 11.14 µm was obtained when the AA8011 was positioned on the A.S. In the TIG + FSPed zone, an intricate vortex flow pattern could be seen. The extremely superplastic flow of plasticized material is seen in the mixed flow zone, which results in a tumultuous intercalation pattern. In situ extrusions of different alloys and severe plastic, deformation was induced by stirring tool action. Lamellae structure was generated by moving the plasticized material layer by layer. In this zone, vigorous mixing and penetration of A6082 and AA8011 were observed. The maximum tensile strength and strain rate of the TIG weldment showed a significant increase after friction stir processing from 83.83 MPa with a strain rate of 23.79% to 90.09 MPa with a tensile strain of 28.04. However, evaluating the FSPed joints, the AA8011-AA6082 specimen had better tensile properties. Moreover, the fracture surface analysis correlated with the tensile tests. The FSPed AA6082-AA8011 joint showed a higher hardness than the AA8011-AA6082 one.
A strategy of powder surface functional modification involving in situ synthesis of carbon nanotubes (CNTs) on Al powder is described to address the poor forming ability and inferior mechanical properties of Al parts produced by laser powder bed fusion. The obtained CNTs-Al composite powder exhibited a combination of high sphericity and flowability of powder, as well as good dispersion uniformity, bonding force and structural integrity of CNTs. The presence of CNTs significantly reduced the laser reflectivity and enhanced the printability of Al powder. The in situ synthesized CNTs contributed to reinforcement after printing and enhanced the tensile properties of printed sample. The printing behavior of powder, the distribution of reinforcement, and the tensile properties of printed sample were optimized by tuning the content of CNTs. The CNT-content in the composite powder was optimized at 0.96 wt% to achieve the synergy of high forming quality, densification and good tensile properties.
Composite materials possess advantages like high strength and stiffness with low density and prove their essentiality in the aviation sector. Aluminium metal matrix composites (AMMC) find applications in automotive, aircraft, and marine industries due to their high specific strength, superior wear resistance, and lower thermal expansion. The fabrication of composites using the liquid phase at high temperature leads to the formation of intermetallics and unwanted phases. Friction Stir Processing (FSP) is a novel technique of composite fabrication, with temperature below the melting point of the matrix, achieving good grain refinement. Many researchers reported enhancement of mechanical, microstructure, and tribological properties of AMMC produced by the FSP route. The FSP parameters such as tool rotational speed, tool traverse speeds are found to be having greater impact on uniform dispersion of particles. It is observed that the properties such as tensile strength, hardness, wear and corrosion resistance, are altered by the FSP processes, and the scale of the alterations is influenced significantly by the processing and tool parameters. The strengthening mechanisms responsible for such alterations are discussed in this paper. Advanced engineering materials like shape memory alloys, high entropy alloys, MAX phase materials and intermetallics as reinforcement material are also discussed. Challenges and opportunities in FSP to manufacture AMMC are summarized, providing great benefit to researchers working on FSP technique.
Friction stir processing (FSP) is a novice material processing technique for modifying the properties of materials. A slight variation from the optimized process parameter can introduce material defects. These material defects are caused due to nonuniform thermal history and inadequate material flow caused by the improper FSP parameters. In this work, the numerical model of FSP was realized using finite volume method for analyzing the effect of process parameters. Mathematical models governing the FSP were reviewed and coded as user defined functions (UDF), which was then compiled inside the fluent environment for calculating various material properties during the simulations. The designed model was validated using a published literature for further simulations. Various combinations of tool traverse speed and tool rotation speed were considered and analyzed using the model. From these simulations, the temperature distributions and material flow were found and analyzed for exploring the effect of parameters.KeywordsFriction stir processingCFDAluminum alloyMaterial flowThermal analysis
The superplastic 7075Al alloy was tested over a range of strain rates 10[sup [minus]2] [minus]10[sup [minus]4]s[sup [minus]1] at a temperature range 430-510C using specimens machined with the rolling direction parallel and perpendicular to the tensile axis. It is shown that the mechanical properties of the alloy, including the elongations to failure, are essentially identical. Microstructural observations show that the cavities tend to form in stringers and these stringers are always oriented along the tensile axis regardless of the rolling direction. The cavities are not nucleated primarily at large Fe-rich or Si-rich particles, nor do they grow from pre-existing microvoids which may be introduced during thermomechanical processing. The cavities are nucleated preferentially at small particles or some irregularities in the grain boundary during superplastic deformation.
Ultrafine grain sizes were introduced into samples of an Al-3 pct Mg solid solution alloy and a cast Al-Mg-Li-Zr alloy using
the process of equal-channel angular (ECA) pressing. The Al-3 pct Mg alloy exhibited a grain size of ∼0.23 µm after pressing
at room temperature to a strain of ∼4, but there was significant grain growth when the pressed material was heated to temperatures
above ∼450 K. The Al-Mg-Li-Zr alloy exhibited a grain size of ∼1.2 µm, and the microstructure was heterogeneous after pressing
to a strain of ∼4 at 673 K and homogeneous after pressing to a strain of ∼8 at 673 K with an additional strain of ∼4 at 473
K. The heterogeneous material exhibited superplastic-like flow, but the homogeneous material exhibited high-strain-rate superplasticity
with an elongation of >1000 pct at 623 K at a strain rate of 10−2 s−1. It is concluded that a homogeneous microstructure is required, and therefore a high pressing strain, in order to attain
high-strain-rate superplasticity (HSR SP) in ultrafine-grained materials.
Friction stir welding (FSW), a new welding technique invented at TWI, was used to weld 7075 T651 aluminum, an alloy considered
essentially unweldable by fusion processes. This weld process exposed the alloy to a short time, high-temperature spike, while
introducing extensive localized deformation. Studies were performed on these solid-state welds to determine mechanical properties
both in the longitudinal direction, i.e., within the weld nugget, and, more conventionally, transverse to the weld direction. Because of the unique weld procedure,
a fully recrystallized fine grain weld nugget was developed. In addition, proximate to the nugget, both a thermomechanically
affected zone (TMAZ) and heat affected zone (HAZ) were created. During welding, temperatures remained below the melting point
and, as such, no cast or resolidification microstructure was developed. However, within the weld nugget, a banded microstructure
that influences room-temperature fracture behavior was created. In the as-welded condition, weld nugget strength decreased,
while ductility remained high. A low-temperature aging treatment failed to fully restore T651 strength and significantly reduced
tensile ductility. Samples tested transverse to the weld direction failed in the HAZ, where coarsened precipitates caused
localized softening. Subsequent low-temperature aging further reduced average strain to failure without affecting strength.
Although reductions in strength and ductility were observed, in comparison to other weld processes, FSW offers considerable
potential for welding 7075 T651 aluminum.
Nanocrystalline materials provide a unique opportunity to investigate deformation mechanisms at an extremely fine microstructural
scale. An intriguing question has been whether the deformation mechanisms scale with grain size to the nanocrystalline range
or whether there are fundamental changes/transitions. The observations of low-temperature and high-strain-rate superplasticity
in nanocrystalline materials with some unique features open up new possibilities for scientific and technological advancements.
The microstructural and mechanical characteristics in superplasticity are briefly reviewed. A model for superplastic deformation is proposed that is based on grain boundary sliding and is controlled by the rate of deformation of the grain interior. A comparison is made of the proposed model and the various creep mechanisms in order to reveal the ranges of conditions over which each mechanism predominates and how the various mechanisms are related one to another. The available experimental data on two superplastic alloys are reviewed in the light of such comparison and it is shown that the trends of such correlation are acceptable.
Superplasticity in powder metallurgy aluminum alloys and composites has been reviewed through a detailed analysis. The stress-strain curves can be put into four categories: a classical well-behaved type, continuous strain hardening type, continuous strain softening type and a complex type. The origin of these different types of stress-strain curves is discussed. The microstructural features of the processed material and the role of strain have been reviewed. The role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined. Threshold stresses have been determined and analyzed. The parametric dependencies for superplastic flow in modified conventional aluminum alloys, mechanically alloyed alloys and aluminum alloy matrix composites is determined to elucidate the superplastic mechanism at high strain rates. The role of incipient melting has been analyzed. A stress exponent of 2, an activation energy equal to that for grain boundary diffusion and a grain size dependence of 2 generally describes superplastic flow in modified conventional aluminum alloys and mechanically alloyed alloys. The present results agree well with the predictions of grain boundary sliding models. This suggests that the mechanism of high strain rate superplasticity in the above-mentioned alloys is similar to conventional superplasticity. The shift of optimum superplastic strain rates to higher values is a consequence of microstructural refinement. The parametric dependencies for superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of 313 kJ mol−1 best describes the composites having SiC reinforcements. The role of shape of the reinforcement (particle or whisker) and processing history is addressed. The analysis suggests that the mechanism for superplasticity in composites is interface diffusion controlled grain boundary sliding.
GB Patent Application No. 9125978
- W M Thomas
- E D Nicholas
- J C Needham
- M G Murch
- P Templesmith
- C J Dawes