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The study on interface and property of TiNb/Zr-based metallic glassy composite fabricated by SPS
Abstract
Abstract In the present study TiNb/Zr55Cu30Al10Ni5 with various fraction additions were fabricated by spark plasma sintering successfully. The interface between the TiNb and the glassy matrix was investigated by nanoindentation. The results indicate that there is a good bonding between them. Therefore, the strength and plastic strain are improved due to introduction of TiNb. In order to study the improved plastic deformation of the composites, the FEM (Finite Element Method) was adopted. It is observed that more shear bands are formed around the TiNb particles. The shear bands form and propagate at the interface of the TiNb and the glassy matrix due to the misfit of their Young's modulus, therefore, the plastic strain is improved.
... First, nanoindentation tests were performed with a coupled analysis in a scanning electron microscope to show the gradient properties the interface between the bulk TA6V [3][4][5] ...
... The possibility to develop the weldability of TiNb/CNTs nanocomposites [3] with TA6V alloys to form TiNb/CNTs/TA6V by sparck plasma sintering is in achived. TiNb/CNTs nanocomposites has required mechanical and chemical properties for this kind of biomedical applications. ...
... Among them, SPS or pulsed electric current sintering (PECS) has attracted special interest due to it allowing high-speed powder consolidation [20,21] and has, therefore, become a promising technique for BMG manufacturing [3]. Several types of BMGs have been manufactured via SPS, seeking applications in different fields: Cu-, Fe-, Ti-, Pb-, Zr-, Niand Al-based [2][3][4]6,[22][23][24][25][26][27][28][29][30][31][32][33][34][35]. The main applications for BMGs include sports equipment, optical mirrors, communication equipment, magnetic applications, or engine components [36,37]. ...
This manuscript proposes subjecting gas-atomized powders of ZrCu39.85Y2.37Al1.8 metallic glass to spark plasma sintering (SPS). This bulk metallic glass (BMG) sinters at a temperature between its crystallization (Tx) and glass transition (Tg) temperatures, found to be 457 °C and 368 °C, respectively, via Differential Scanning Calorimetry (DSC). Several samples were sintered at different temperatures within the mentioned range (380, 390, 400, 415 and 430 °C). Experimental results confirmed successful sintering of the BMG by SPS at 390 °C and a pressure of 35 MPa. Fully amorphous compacts with almost 100% relative density were sintered at this temperature, reaching Young's modulus, Vickers hardness and compression strength values of 64.7 GPa, 396 HV0.3 and 1174 MPa, respectively. Sintering at higher temperatures involved crystallization of the sample. Results suggest that ZrCu39.85Y2.37Al1.8 metallic glass fabricated by SPS is a promising material for applications in different sectors, particularly jewelry, due to the wear resistance conferred by its hardness.
... The ultimate aim of this work is to demonstrate the biomaterials TiNb alloys, TiNb/CNTs [3] nanocomposites and TiNb/CNTs/TA6V after welding by FASPS has the required mechanical and chemical properties for this kind of biomedical applications. First, nanoindentation tests were performed with a coupled analysis in a scanning electron microscope to show the gradient properties the interface between the bulk TA6V [7][8][9] and the TiNb, TiNb/CNTs, bulk biomaterials. ...
Nanocomposite Ti 50 wt% Nb with and with about reinforcement
of carbon nanotubes were successfully fabricated by ball milling
of Ti, Nb and SWCNTs (single walled carbon nanotubes) nanopow-
der mixture folloyed by field actived spark plasma sintering process
(FASPS) for biomedical application, superconductivity and magne-
tism in the ITER Project. The use of brittle Ti powder, instead of duc-
tile elemental powder, led to significant increment in the yield of me-
chanically alloyed powder. The powder consisted of homogeneously
distributed nano-sized Ti/Nb particles together with micron-sized
pure Nb particles. Sintering of the powders under low temperature
and pressure conditions (1273 K, 1473 K and P=50 Mpa) result-
ed in the fine-grained heterogeneous microstructure consisting of α
and β phases. On the other hand, sintering at higher temperatures
(1473 K) resulted in a relatively coarse-grained chemically homoge-
neous microstructure with almost complete phase. Coarse-grained
homogeneous β NbTi alloy exhibited higher average hardness as
compared to that of heterogeneous fine grained microstructures.
An attempt has been made to illustrate the correlation between the
microstructural characteristics and mechanical properties of the
sintered Ti50Nb compacts. To studies and to develop the influence
of SWCNTs on the behavior of the nanocomposite TiNb/SWCNTs
and the welding joint interface between TA6V and nanocomposite
by sparck plasma sintering. At last, the continuation of the work
has been discussed and prepared, planning dynamic flexion tests
to measure the NbTi, NbTi/CNTs, NbTi/SWCNTs,/TA6V fatigue limit
and developing a computer processing chain in order to customize
prostheses respecting patients’ morphology. The fluid ethanchied lu-
brification of the prosthesis articulation is currently also in study and
preparation.
Then, a change of scale made possible by the use of an industrial
size SPS machine led to the realization of types of blade preform
according to patient morphology. These results led to the filing of a
patent.
Keywords: Biomechanic; Friction coefficient; NbTi50; Nano-inden-
dation; Single walled carbon nanotubes (SWCNTs); Stress-shielding; Titanium alloys
... /CNTs/TA6V after welding by FASPS has the required mechanical and chemical properties for this kind of biomedical applications. First, nanoindentation tests were performed with a coupled analysis in a scanning electron microscope to show the gradient properties the interface between the bulk TA6V[7][8][9]and the TiNb, TiNb/CNTs, bulk biomaterials. Scratch and wear tests were used to study the tribological properties of this titanium alloy nanocomposite in comparison with welded with TA6V. ...
... Other numerical simulations on the deformation of BMGCs just focused on the effect of a certain individual microstructural feature. For example, Chu et al. [31] only discussed the effect of the interface on the compressive deformation of the Zr-based BMG composites; Jeon et al. [32] only analyzed the influence of the effective dendrite size on the deformation of BMGCs. ...
The free volume model is firstly extended to describe the asymmetry of bulk metallic glass (BMG) presented under the uniaxial tensile and compressive deformations, and then the extended model is implemented into a finite element code as a user material subroutine (UMAT). Based on such a UMAT, a systematic numerical simulation is performed to investigate the deformation behaviors of BMG composites subjected to uniaxial tensile and compressive loadings. The von-Mises equivalent shear plastic strain is adopted to characterize the nucleation and propagation of shear bands in the BMG matrix here. The simulated uniaxial tensile overall stress–strain responses of the BMG composites containing different volume fractions, shapes, orientations and yielding stresses of toughening particles are compared with the compressive ones. It is shown that the initiation and propagation of shear bands in the BMG composites depend on the geometric features and yielding stresses of the toughening particles and present obviously different evolution features under the uniaxial tension and compression. The obtained results are very useful for designing and modeling the BMG composites.
... In the past decade the deformation of BMGMCs has attracted increasing research interest [19,20,21,22]. ...
The aim of this study was to evaluate new Zr-based bulk metallic composites with crystallized dendrites or droplets which have the volume fraction below the critical one (the percolation limit). The Cu36Zr48Al8Ag8 alloy was chosen as matrix. Dendrites formed by in-situ solidification due to Ni addition. It was found that a new monotectic alloy system can be created successfully owing to Y addition (1–7 at.%) to the matrix. Small amount of dendrites with non-random distribution has a strong influence on the compressive strength. Experiment showed that the alloy with 4.1 at.% Ni has the maximum compressive strength (1998 MPa) and Young's modulus (86 GPa) within the examined samples. The results of compression test reveal that the cracks propagate near the small droplets below 1 μm in diameter which generate weakening in the microstructure. In contrast, the large droplets especially above 3 μm in diameter create a strong barrier for the shear band propagation.
... The deficiency of crystalline structure provides BMGs with a diversity of attractive properties such as mechanical properties, strong corrosion resistance and unique processability in the supercooled liquid state [1]. Zr-based BMGs, which possess good glass-forming ability (GFA), low Young's modulus, high elastic limit and strength as well as excellent wear and corrosion resistance, have been attracted the attention of researchers in recent years [1][2][3][4][5][6][7][8]. Whereas, most of the Zr-based BMGs developed to date contain Ni element, which is allergic and possibly carcinogenic for the human body [9]. ...
Isothermal annealing has been used to improve the mechanical properties and the pitting corrosion resistance of a new bulk metallic glass (BMG) alloy, Zr65Cu17.5Fe10Al7.5. The as-cast alloy was annealed at the temperature below the glass transition temperature (Tg) for 0.5, 1.0, 2.0, and 4.0 h. A considerable large plasticity of 7.1% is achieved in the alloy annealed for 1.0 h without loosing its strength, which can be attributed to the formation of nanocrystallites with diameter 5–12 nm in the glassy matrix. In addition, presumably due to the decrease in the free volume, appropriate annealing (t = 0.5 and 1.0 h) can increase the pitting corrosion resistance significantly of the as-cast alloy. Thus, Zr-based metallic glass matrix composite has a promising potential for engineering and biomedical applications.
In this work, we prepared equiatomic AlCoCrFeNi high-entropy alloy (HEA)-particle-toughened, Zr-based metallic glass composites by spark plasma sintering. By adding HEA particles as the second phase, the strength and plasticity of the Zr-based metallic glass composites improved concomitantly. After fracture, High-density dislocations and nanocrystals were formed in the HEA particles due to local severe plastic deformation, which consumed massive strain energy to enable the resistance to crack formation. Substantial lattice distortion imparted a remarkable work-hardening capacity to the HEAs and enhanced crack-tip dislocation trapping, and thus led to an extreme refinement of the grain size. Finite-element analyses indicated that the strain hardening behavior of HEA particles reduced the magnitude of strain localization, promoted generation of multiple shear bands, and stabilized shear band propagation. We attribute the enhanced strength-ductility synergy in the current composites to high-density dislocations and nanocrystal formation in the HEA particles, and stable propagation of multiple shear bands.
Nanocomposite Ti 50 wt% Nb with and without reinforcement of carbon nanotubes were successfully fabricated by ball milling of Ti, Nb and SWCNTs (single walled carbon nanotubes) nanopowder mixture folloyed by field actived spark plasma sintering process (FASPS) for biomedical application, superconductivity and magnetism in the ITER Project. The use of brittle Ti powder, instead of ductile elemental powder, led to significant increment in the yield of mechanically alloyed powder. The powder consisted of homogeneously distributed nano-sized Ti/Nb particles together with micronsized pure Nb particles. Sintering of the powders under low temperature and pressure conditions (1273 K, 1473 K and P=50 Mpa) resulted in the fine-grained heterogeneous microstructure consisting of α and β phases. On the other hand, sintering at higher temperatures (1473 K) resulted in a relatively coarse-grained chemically homogeneous microstructure with almost complete phase. Coarse-grained homogeneous β NbTi alloy exhibited higher average hardness as compared to that of heterogeneous fine grained microstructures. An attempt has been made to illustrate the correlation between the microstructural characteristics and mechanical properties of the sintered Ti50Nb compacts. To studies and to develop the influence of SWCNTs on the behavior of the nanocomposite TiNb/SWCNTs and the welding joint interface between TA6V and nanocomposite by sparck plasma sintering. At last, the continuation of the work has been discussed and prepared, planning dynamic flexion tests to measure the NbTi, NbTi/CNTs, NbTi/SWCNTs,/TA6V fatigue limit and developing a computer processing chain in order to customize prostheses respecting patients’ morphology. The fluid ethanchied lubrification of the prosthesis articulation is currently also in study and preparation. Then, a change of scale made possible by the use of an industrial size SPS machine led to the realization of types of blade perform according to patent morphology. These results led to the filing of a patent.
In this work, the particle-reinforced 7056 Al alloy/ Zr-Al-Ni-Cu metallic glass composites were successfully prepared by spark plasma sintering (SPS) combined with gas atomization at different loading pressures (45 and 400 MPa). No crystallization was observed throughout the composite and 7056 Al alloy particles were uniformly distributed in the glassy matrix. Due to enhanced densification, higher loading pressure (400 MPa) greatly increased the relative density of the composite from 95% to over 98% and its room-temperature compressive strength. When volume fraction of Al alloy was less than 10 vol%, the strength of the composite was higher than that of pure monolithic BMG obtained by SPS, and its plasticity was also improved. With the higher content of Al alloy, the plasticity of the composite continued to increase, but its strength decreased significantly. With the higher volume fraction of Al alloy (≥30 vol%), yield strength of the composites was accurately described by the iso-stress model. Interface characteristics were investigated by scanning electron microscopy (SEM), nanoindentation and high-resolution transmission electron microscopy (HRTEM). The increase in loading pressure from 45 to 400 MPa caused glassy matrix and Al alloy reinforcement to bond each other more tightly and destroyed the oxide layer at the interface, resulting in an effective increase in the bonding strength of the two-phase interface. A transition layer (∼15 nm) occurred at the interface, and some elements such as Zr, Mg and Zn diffused into the interface between glassy matrix and Al alloy particle.
New 7056 aluminum alloy matrix composites reinforced with Zr55Al10Ni5Cu30 metallic glassy particles are successfully fabricated by spark plasma sintering (SPS) combined with gas‐atomization method. The highly dense bulk body is obtained by utilizing the viscous flow behavior of the glassy powder within the supercooled liquid region. The addition of amorphous reinforcing phase significantly increases the yield strength of Al alloys in compression from 322 to 455 MPa, with retaining a fracture strain ranging between 26% and 16%. It is confirmed that the mutual diffusion of elements takes place between Al alloy matrix and glassy reinforcement during SPS process. The imposed stress and temperature by SPS affect the mutual diffusion and elemental distribution at interface. The increased mechanical response is ascribed to the uniform distribution of the glassy particles and good interfacial bonding. The mechanical properties of such composites can be accurately described by the iso‐stress model involving the matrix‐strengthening mechanism.
Spark plasma sintering (SPS) of metallic glasses (MG) can be quite different from sintering crystalline metallic alloys. Indeed, MG behave differently with increasing temperature, as they encounter a glass transition and devitrification. Their shaping can thus be compared to what can be performed on thermoplastic polymers. SPS is a promising way to prepare bulk parts from amorphous powders, since it allows very fast heating and cooling rates. It gives an advantage to avoid or limit devitrification of the amorphous phase upon the thermal cycle. However, diffusion mechanisms, which generally control densification, are activated at temperatures that are not compatible with MG structural integrity. From a manufacturing point of view, one has thus to find the best compromise to achieve full density and optimal properties without degrading the amorphous phase.
A preliminary study has shown that bulk metallic glasses of the CuZrAl type of large dimension may be manufactured from amorphous powders densified by a process of sintering such as spark plasma sintering (SPS). However, to remedy the lack of plasticity of these materials, the addition of ductile crystalline particles was carried out in the present study. The zirconium was chosen because its properties are close to those of the amorphous matrix. The same sintering parameters as those optimized for the metallic glass are also applicable for the production of the composite for the different zirconium volume fractions retained, respectively 5%, 10%, 20%, 30%, 40% and 50%. The materials obtained are dense. X-ray diffraction clearly indicates that only the amorphous matrix CuZrAl and the crystalline zirconium are present. Young's modulus as well as the elastic limit decrease only very slightly with the addition of crystalline particles. Decrease in hardness is more pronounced. On the other hand, the plastic deformation increases with the addition of zirconium, reaching about 4.9% for the alloy containing 50% zirconium. The analysis of the fracture surfaces clearly shows the role of the ductile crystalline particles, namely the deceleration of the shear bands. The influence of volume fraction and size of the crystalline particles and of matrix toughness is discussed from a mechanical point of view.
Therefore, SPS is a solution to solve both the problem of size and low ductility of amorphous metal, since it is possible to control microstructure and so to control mechanical properties.
A significant enhancement of yield strength and large plasticity was obtained in TiNb/Zr55Cu30Al10Ni5 composite by cyclic compression at the yield point. This phenomenon resulted from the cooperation of the metallic crystalline alloy TiNb and metallic glassy matrix Zr55Cu30Al10Ni5 in the composite. It was found that a large dislocation density of TiNb was produced during cyclic compression, which resulted in the increase of the strength. Meanwhile, the improvement of plasticity of the composite benefited from the propagation of excess shear bands in the glassy matrix, which were produced during the cyclic compression process. Hence, the collective effect of both resulted in the improved yield strength and large plasticity of the composite.
This paper aims to review our recent data on the development researches and applica-tion examples of bulk glassy alloys. Very recently, the glass-forming ability of metallic alloys is significantly enhanced by further multiplication of alloy components based on the three compo-nent rules for bulk glass formation. The maximum diameter for glass formation exceeds 10 mm in a variety of alloy systems such as Zr, Pd, Pt, Mg, La, Fe, Co, Ni, and Cu bases. By use of high glass-forming ability, good castability, good printability and unique characteristics, application ex-amples of bulk glassy alloys have been extended to much valuable fields in which conventional crystalline alloys cannot be used. These novel advantages for bulk glassy alloys allow us to con-clude that bulk glassy alloys are used in much wider application fields in the near future.
In situ devitrification and consolidation of gas atomized Al87Ni8La5glassy powders into highly dense bulk specimens was carried out by spark plasma sintering. Room temperature compression tests of the consolidated bulk material reveal remarkable mechanical properties, namely, high compression strength of 930 MPa combined with plastic strain exceeding 25%. These findings demonstrate that the combined devitrification and consolidation of glassy precursors by spark plasma sintering is a suitable method for the production of Al-based materials characterized by high strength and considerable plastic deformation.
Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb beta phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass.
In the absence of dislocation-mediated crystallographic slip, room-temperature deformation in metallic glasses occurs in thin shear bands initially only ∼10 nm thick. A sharp drop in viscosity (shear softening) occurs in deformed glassy matter and facilitates additional flow in existing shear bands. This further localization of plastic flow leads to shearing-off failure without any significant macroscopic plasticity.
However, whereas most bulk metallic glasses fail in this manner, some undergo surprisingly extensive plastic deformation (in some cases, up to 50% or more) in compression or bending. When this occurs, the flow is “jerky,” as indicated by serrated stress–strain curves. Each serration may correspond to the emission of a shear band that then ceases to operate, at least temporarily, despite the predicted shear softening. As elastic energy is converted to heat during shear, temperatures rise sharply at or near shear bands. This heating may lead to the growth of nanocrystals that then block propagation of shear bands and cracks. The understanding of the dependence of mechanical response of metallic glasses on intrinsic (elastic constants, chemistry) and extrinsic factors (shapes, flaws) is the subject of intense current interest.
The mechanical properties of amorphous alloys have proven both scientifically unique and of potential practical interest, although the underlying deformation physics of these materials remain less firmly established as compared with crystalline alloys. In this article, we review recent advances in understanding the mechanical behavior of metallic glasses, with particular emphasis on the deformation and fracture mechanisms. Atomistic as well as continuum modeling and experimental work on elasticity, plastic flow and localization, fracture and fatigue are all discussed, and theoretical developments are connected, where possible, with macroscopic experimental responses. The role of glass structure on mechanical properties, and conversely, the effect of deformation upon glass structure, are also described. The mechanical properties of metallic glass-derivative materials – including in situ and ex situ composites, foams and nanocrystal-reinforced glasses – are reviewed as well. Finally, we identify a number of important unresolved issues for the field.
The (Zr48Cu36Al8Ag8)99.25Si0.75-based bulk metallic glass composite (BMGC) rods ex situ dispersed with Ta particles (with a diameter of 2–4mm) have been successfully fabricated by suction casting and characterized. These Ta-added BMGCs exhibit similar thermal properties in comparison with its base alloy counterpart, with relatively high glass forming ability (GFA). The results of compression test show that a superior mechanical performance with up to 22% compressive plastic strain, 1800MPa yield strength and 1850MPa fracture strength at room temperature can be obtained for the 2mm diameter rod of the ZrCu-based BMGC with 10vol.% Ta particles. These ex situ dispersed Ta particles (20±8μm) would arrange as semi-uniform confinement zones to restrict the shear band propagation. In addition, for a given Ta particle size, higher volume fraction particles would lead to more interfacial areas, shorter inter-particle spacings, smaller confinement zone sizes than the smaller volume fraction particles, and results in presenting larger compression plasticity.
Instrumented sharp indentation experiments using both conical and Vickers diamond pyramidal indenters were carried out to study deformation characteristics of Zr55Cu30Al10Ni5 bulk metallic glass. Finite element simulations of instrumented indentation were also performed to formulate an overall constitutive response. Comparing the experimentally obtained results with the finite element predictions, it can be stated that mechanical deformation of the bulk metallic glass can be described well by both Mohr–Coulomb and Drucker–Prager constitutive criteria. Using these criteria, the extent of material pile-up observed around the indenter was also estimated very well.
Some recent experiments on sub-micron and nano-sized metallic glass (amorphous alloy) specimens have shown that the shear localization process becomes more stable and less catastrophic when compared to the response exhibited by large sample sizes. This leads to the discovery that the shear localization process and fracture can be delayed by decreasing sample volume. In this work we develop a non-local and finite-deformation-based constitutive model using thermodynamic principles and the theory of micro-force balance to study the causes for the aforementioned observations. The constitutive model has also been implemented into a commercially available finite-element program by writing a user-material subroutine. With the aid of finite-element simulations, our constitutive model predicts that metallic glass samples have the intrinsic ability to exhibit: (a) the delaying of (catastrophic) shear localization with decreasing sample size, and (b) homogeneous deformation behavior for sample volumes smaller than the shear band nucleus.The cause for the observations listed above is the increasing influence of a non-local interaction stress with decreasing sample volume. This interaction stress has energetic origins and it affects plastic deformation due to the strong coupling between plastic shearing and free-volume generation. Akin to strain-gradient plasticity theory, the role of the interaction stress is to strengthen the material at locations where the defect density/free volume is higher compared to the rest of metallic glass sample.
Two-type sintered specimens of Zr55Cu30Al10Ni5 glassy alloy powder blended with and without 10 vol% ZrO2 ceramic powder, which had the similar relative density, were fabricated by a spark plasma sintering process in order to clarify the reinforced mechanical effect of ZrO2 particulates in the metallic glassy matrix composite. The structure, thermal stability and mechanical properties of the two-type sintered specimens were investigated. Two-type sintered specimens as well as original metallic glassy powder exhibited similar thermal stability. No crystallization of the metallic glassy matrix was demonstrated during the spark plasma sintering process. The plastic ductility of the sintered Zr55Cu30Al10Ni5 glassy matrix composite was enhanced by adding the ZrO2 particulates into the metallic glassy alloy. The improvement was originated from the Structural inhomogeneity caused by the micro particles inclusion.
In uniaxial compressive deformation of Pd40Ni40P20 glass the angle between the plane of the shear bands and the compression axis is observed to be approximately 42°, increasing with compressive strain. This indicates that the yield process is dependent on the normal stress acting on the slip plane. The yield stress in plane strain compression is almost equal to the yield stress in uniaxial compression. Both these observations show that yielding in this glass is controlled by a Mohr-Coulomb or Tresca criterion, rather than the von Mises criterion appropriate for crystalline metals, and this confirms that the flow mechanism is intrinsically different from that in crystalline metals and similar to that which operates in amorphous polymers which dilate during flow.
The yield strength of Pd40Ni40P20 metallic glass undergoing low-temperature, localised plastic flow has been measured in uniaxial compression, plane-strain compression, pure shear and tension. The results demonstrate that yielding in Pd40Ni40P20 follows a Mohr-Coulomb criterion, rather than the von Mises criterion which is appropriate to polycrystalline metals. The sign of the normal stress acting across the slip-plane has a significant effect on the yield strength so that the yield strength in compression is substantially higher than in tension, but the hydrostatic pressure has only a small effect on yielding. This result is discussed in terms of the micromechanism of plastic flow in metallic glasses.
In the present study, Ti50Cu28Ni15Sn7 metallic glass and its composite powders reinforced with 4–12vol.% of Al2O3 added were successfully prepared by mechanical alloying. In the ball-milled composites, an amorphous matrix with a homogeneous dispersion of Al2O3 particles was developed. The metallic glass composite powders were found to exhibit a large supercooled liquid region before crystallization. The presence of Al2O3 particles did not change the glass formation ability of the amorphous Ti50Cu28Ni15Sn7 powders. Consolidation of the as-milled Ti50Cu28Ni15Sn7 composite powders was performed at a temperature slightly higher than the glass transition temperature under a pressure of ∼1.2GPa; using this method, the bulk metallic glass composite discs were prepared successfully. However, partial crystallization of the amorphous matrix during the hot-pressing process was noticed. The fracture strength of consolidated composite compacts was increased with Al2O3 additions. The pre-existing particle boundaries may serve as the crack initiation sites which resulted in the brittle failure of the Ti50Cu28Ni15Sn7 BMG composites.
In this study, the atomic composition of Mg58Cu28.5Gd11Ag2.5 which possess high glass forming ability (GFA) was selected as the matrix alloy for synthesizing the ductile Fe particles-reinforced Mg-based bulk metallic glass composites (BMGCs) by using injection casting method. The results show that the compressive ductility increases with the volume fraction of Fe particles and reaches up to the compressive plastic strain of 8% for the Mg-based BMGC with 20vol.% Fe. In parallel, multiple-shear bands were revealed on the sample surface which is near the fracture area. This suggests that these Fe particles can branch primary shear band into multiple-shear bands and decrease the stress concentration for further propagation of shear band, and so as to enhance plasticity. Additionally, a slightly decreasing in yield strength with increasing the addition of Fe particles was found presumably due to the formation of brittle Fe2Gd intermetallic phase at the interface between the Fe particle and amorphous matrix. In overall, the ductile Fe dispersoids would provide a good toughening effect in promoting the practical use of amorphous materials.
Amorphous Ti50Cu28Ni15Sn7 alloy powders were synthesized by a mechanical alloying (MA) technique. Differential scanning calorimetry (DSC) results showed
that, after 7 hours of exposure to the milling process, amorphous Ti50Cu28Ni15Sn7 alloy powders exhibit a wide supercooled liquid region of 61 K. Consolidation of amorphous powders were performed at a temperature
slightly higher than the glass transition temperature under a pressure of ∼1.2 GPa, and bulk metallic glass (BMG) discs can
be prepared successfully. However, we noticed partial crystallization during the hot pressing process and were not able to
achieve full densification of BMG. The Vickers microhardness of Ti50Cu28Ni15Sn7 BMG was 634 kg/mm2, and the trace of the indentation revealed that pre-existing particle boundaries or interfaces between nanocrystals and amorphous
matrix may serve as the crack initiation sites. Thus, typical brittle failure of Ti50Cu28Ni15Sn7 BMG was observed and resulted in relatively low fracture stress compared to that estimated by the microhardness.
Bulk metallic glass composites containing constituent phases with different length-scales are prepared via an in situ method by copper mold casting homogeneous Zr–Ti–Nb–Cu–Ni–Al melts. The phase formation and the microstructure of the composite materials are investigated by X-ray diffraction, optical, scanning and transmission electron microscopy, and microprobe analysis. The composition of the melt as well as the cooling conditions realized during casting determine the type and the morphology of the phases present in the composite. The mechanical properties of composite materials with quasicrystalline or ductile bcc phase reinforcements are tested in uniaxial compression at room temperature, showing that the deformation is controlled by the type of the constituent phases and their morphology. Ductile phase-containing metallic glass composites demonstrate improved work hardening and ductility compared to monolithic metallic glasses. Similar results are obtained for composites with ductile bcc phase dendrites embedded in a nanocrystalline matrix. The improved ductility of the composites is due to the presence of the ductile second phase, which counteracts catastrophic failure by shear localization.
The authors report the synthesis of Mg-based metallic glass composite reinforced with Nb particles which are simply added during melting process. The ductile Nb particles effectively impede shear band propagation and upon yielding, deformed Nb particles distribute the load uniformly to the surrounding glassy matrix to promote the initiation and branching of abundant secondary shear bands. In contrast to the previous Mg-based metallic glass composites which fracture with very little plasticity, the composite shows great resistance to crack growth. The high strength of 900 MPa and large plasticity of 12.1±2% have made it comparable to excellent Zr- or Ti-based metallic glass composite.
The widespread enthusiasm for research on bulk metallic glasses is driven by both a fundamental interest in the structure and properties of disordered materials and their unique promise for structural and functional applications. Unlike the case for crystalline materials, the disordered and nonequilibrium nature of metallic glasses causes their underlying deformation mechanisms to be poorly known. A definite correlation between mechanical behavior and the atomic/electronic structures of metallic glasses has not been established. In this article, I focus on the micromechanisms of mechanical behavior of metallic glasses and present a brief overview of the current understanding of their strength, ductility, and plasticity at the microscopic and atomic scales. The important factors that control the mechanical behavior of metallic glasses are outlined on the basis of recent theoretical and experimental findings. The outstanding issues highlighted in this review are expected to be important for future research ...
Mechanical properties of bulk Zr 60 Cu 20 Pd 10 Al 10 nanocrystalline composite and Zr 55 Ni 5 Cu 30 Al 10 metallic glass were measured by compression tests at room temperature. The Zr 60 Cu 20 Pd 10 Al 10 as-quenched alloy obviously exhibits plastic strain while no distinct plastic deformation is recognized in the Zr 55 Ni 5 Cu 30 Al 10 metallic glass. Moreover, the plastic strain increased by increasing the volume fraction of nanocrystals and achieved maximum value in the early stage of the nanocrystallization. High-resolution electron microscopy showed that, different from the microstructure of Zr 55 Ni 5 Cu 30 Al 10 metallic glass, nanocrystals with main grain sizes of about 2 nm were embedded in the amorphous matrix of the bulk Zr 60 Cu 20 Pd 10 Al 10 alloy which showed the maximum plastic strain. © 2000 American Institute of Physics.
Ni-based bulk metallic glasses (BMGs) with a large size were fabricated by spark plasma sintering (SPS) of a gas-atomized Ni 52.5 Nb 10 Zr 15 Ti 15 Pt 7.5 glassy alloy powder. The structure and thermal stability of the sintered specimens as well as the interface characteristics between powder particles were investigated. The sintered glassy specimens with nearly 100% relative density were obtained by the SPS process at a sintering temperature of 773 K with a loading pressure of 600 MPa . It was achieved using relatively low sintering temperature, short holding time, and rapid cooling during the SPS process. The results suggest that the BMGs fabricated by the SPS process opens possibilities of application as structural materials offering excellent properties and satisfying large-size requirements.
Using the mixed powders of the gas-atomized Ni-based metallic glassy alloy powder blended with metal W or ceramic SiC particulates, we fabricated large-size bulk glassy alloy composites (GACs) by a spark plasma sintering (SPS) process. The microstructure and mechanical properties of the prepared GAC specimens were investigated, and the effect of addition amount of the crystalline particulates on the properties of the sintered GAC specimens was discussed. The Ni-based bulk GACs with ultrahigh strength and enhanced plasticity were produced. The improvement of plasticity of the fabricated bulk GACs is attributed to the structural inhomogeneity caused by the addition particulates inclusion. The optimum content of the crystalline particulates is about 5–10 vol.%.
The Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass forming liquid is reinforced with up to 50 Volume-percent (% Vf) Ta, Nb, or Mo particles. An extensive reaction layer of varying composition formed in the metallic–glass matrix surrounding the particles. A characterization based on X-ray diffraction, differential scanning calorimeter, electron microprobe, and scanning electron microscopy is presented. The composites were tested in compression and tension. Compressive strain-to-failure increased by up to a factor of 12 compared to the unreinforced Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass. The increase in compressive strain-to-failure is due to the particles restricting shear band propagation, promoting the generation of multiple shear bands and additional fracture surface area.
The Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass forming liquid is reinforced with WC, SiC, W, or Ta particles. Structure, microstructure and thermal stability of the composites are studied by X-ray diffraction, optical microscopy and differential scanning calorimetry. The metallic glass matrix remains amorphous after adding up to 20 vol.% of particles. The reactions at the interfaces between the matrix and the different reinforcing materials are investigated with scanning electron microscopy, transmission electron microscopy and electron microprobe. The mechanical properties of the composites are studied in compression and tension. The influence of the introduced particles on the thermal stability of the matrix as well as on the mechanical properties is discussed.