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The stress-strain curves for AA3003/AA6111/AA3003 and the monolithic components of the clad package.  

The stress-strain curves for AA3003/AA6111/AA3003 and the monolithic components of the clad package.  

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Article
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The tensile and bending response of AA3003/AA6111 sheet produced by direct chill casting has been investigated. It is shown that the interface strength of the clad sheet has a minimum value of 175MPa, and failure does not occur in the interface. The yield strength of the clad sheet obeys the rule of mixtures, and up to a cladding thickness of 100μm...

Citations

... The microstructure and texture evolution during bending of the AA6016 alloy was studied in great detail by Sabat et al. [47] and Muhammad et al. [48][49]. Lloyd et al. [50] also reported about the tensile and bending behavior of AA6111 cladding with 100-micrometer layers of AA3003 using direct chill fusion casting technology. ...
Article
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The cyclic shear test of 6063 aluminum alloys under T4 and T6 conditions was carried out at room temperature. The microstructure and texture evolution were investigated using electron backscattered diffraction (EBSD) at several instances during cyclic shear deformation. Hardly any change in grain size was observed during the cyclic shear test of T4 and T6 samples. The local residual strain distribution measured in the form of average kernel misorientations (KAM) values increases continuously with an increase in shear strain for both samples. The increase in KAM value was higher for the T6 sample compared to the T4 sample during forward (F) shearing. On reversing the loading path, the increase in KAM value was higher for forward + reverse (FR) and forward + reverse + forward (FRF) straining of the T4 sample compared to the T6 sample. The cube texture was found to be unstable during shear deformation. A significant rotation of texture was observed in both T4 and T6 samples. However, the extent of rotation was slightly greater for the T6 sample as compared to the T4 sample. It was observed that the latent hardening of (1̅11) <101> was more θ (111) <1̅01> in the T4 sample. Similarly, the latent hardening of (1̅1̅1) <011> was more than the (111) <1̅01> in the T6 sample. The origin of latent hardening was attributed to the formation of sessile jogs during dislocation-dislocation interactions on different planes of T4 samples and the difference in volume fraction of precipitates on different planes of T6 samples. The mechanical properties show that the 0.2% YS increases with subsequent reverse and forward shearing for the T4 sample. However, the 0.2% YS during subsequent reverse shearing is lower than the initial forward shearing for the T6 sample. This decrease in yield stress upon loading reversal is attributed to the presence of deformation-induced intragranular back stresses within the T6 material. It is observed that the rate of cross slip of dislocations depends on the athermal dislocation content, presence of dislocation debris in the unfavorable grains, and the difference in the latent hardening values of different slip systems for the T4 and T6 materials.
... Bending is an important property in sheet metals as bending occurs as a part of several forming operations, such as in deep drawing in auto industry [1][2][3][4]. In [5][6][7], the bending properties of various materials have been studied, and in [8,9] bending performance was studied using the three-point bend test. ...
Article
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The effect of the width to thickness ratio on the bendability of sheet metal is investigated using the finite element method (FEM) employing the Gurson–Tvergaard–Needleman (GTN) model. Strain path changes in the sheet with change in the width/thickness ratio. It is shown that bendability and fracture strain increase significantly by decrease in the width/thickness ratio. The stress state is almost uniaxial when the stress ratio (α) is close to zero for narrow sheets. Stress ratio is nothing but the major stress to minor stress ratio. This delays the growth and coalescence of micro-voids as the volumetric strain and stress triaxiality (pressure/effective stress) decrease. On the other hand, ductility decreases with increase in α for wider sheets. Fracture bending strain is calculated and, as expected, it increases with decrease in the width/thickness ratio. Furthermore, a brief study is performed to understand the effect of superimposed hydrostatic pressure on fracture strain for various sheet metals with different width/thickness ratios. It is found that the superimposed hydrostatic pressure increases the ductility, and that the effect of the width/thickness ratio in metals on ductility is as significant as the effect of superimposed hydrostatic pressure. Numerical results are found to be in good agreement with experimental observations.
... By combining two kinds of metal materials with different properties by special means, the layered composite material can give full play to the advantages of the two materials and overcome their disadvantages to meet the performance requirements of complex working conditions. Bimetallic layered composites have been widely used in the industrial field [6]. Welding is a common means to combine different materials, such as friction stir welding [7], gas metal arc welding [8], laser beam machining [9], etc. Rolling can also combine plate-like heterogeneous materials at certain temperatures and pressures, such as cold rolling or hot rolling [10]. ...
Article
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The requirements of high-strength, wear-resistance and lightweight of brake drums have been continually increasing in recent years and any specific aluminum alloy or particle-reinforced aluminum matrix composites may not satisfy all the demands. Combining dissimilar materials to play their respective advantages is a solution to this problem. In this study, a compound casting method was used to combine solid SiCp/A357 composite and a liquid 7050 aluminum alloy to prepare an aluminum matrix composite with a layered structure. The ProCAST numerical simulation software was used to predict the heat transfer in compound casting process and guide the preheating temperature of the wear-resistant ring in the experiment. An Optical Microscope (OM) and Scanning Electron Microscope (SEM) were used to observe microstructures around the solid–liquid bonding interface, the element distribution and phase component of which were analyzed by Energy Dispersive Spectroscopy (EDS) and mechanical properties were evaluated by microhardness and shear tests. The results showed that the interface of the layered aluminum matrix composite prepared by this method achieved complete metallurgical bonding and a transition zone formed on the solid surface. After T6 heat treatment, the average shear strength of the interface increased from 19.8 MPa to 33.8 MPa.
... Since 1970s, the technology has been extensively used to produce aluminium brazing sheets for automotive heat exchangers, while AA4xxx Al-Si filler is bonded on the surface of solid solution hardened AA3xxx Al-Mn-Cu [3,4]. In the recent years, the technology has also been used to fabricate highly bendable aluminium sheets for automotive skin applications, by cladding ductile AA3003 Al-Mn on heat treatable AA6xxx Al-Si-Mg-(Cu) [5,6]. ...
Article
An in situ hot press bonding technology has been developed to clad aluminium on magnesium. Followed by regular hot rolling, magnesium sheets, covered by ductile and corrosion-resistant aluminium without detectable oxides in the interface, are produced. The new technology requires no welding, vacuum, protective atmosphere or barrier layer, and it makes good interfacial strength and rollability. Aluminium–magnesium intermetallic phases are formed along the clad–core interface at elevated temperatures. They are not detrimental under compression but may cause clad-core delamination in tensile strain. However, the tensile failure is more dependent on the formability of magnesium core than on the strength of interface.
... Jin et al. [32] investigated the bending behavior of AA2124 sheets cladded with AA1200, and the authors reported significant improvement in bendability of the developed composite alloy. Lloyd et al. [33] and Jin and Lloyd [34] studied the bendability of AA6111 sheets cladded with thin layers of AA3003, produced using direct chill casting. The authors have shown that the ductile clad layer delays the onset of micro-cracking along the outer tensile surface, thereby improving bendability. ...
... Majority of such bands are emanating from locations of local thinning within the clad layer and the surface rumpling behavior has further intensified. Such local thinning and surface rumpling behavior is previously reported by Lloyd et al. [33] in their experimental study of AA3003/AA6111 clad system. As the clad layer thickness is reduced to 60 microns, a micro-crack initiates within the less ductile core in vicinity of the clad-core transition region, as the bending strains are reasonably high in that area (see magnified image in Figure 19(c). ...
Article
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In this study, the sequence of microstructural events leading to failure and the relationship between crystallographic texture, shear band development, micro-crack initiation and propagation during wrap-bending of monolithic AA6016 and composite AA6016X sheet alloys are studied using crystal plasticity based finite element methods (CPFEM). The numerically predicted results for texture evolution, shear bands development and fracture behavior after wrap bending show good agreement to the corresponding experimental observations. It is shown that failure during bending of AA6016 is controlled by the development of intense shear bands that emanate from surface low cusps along the outer tensile edge and provide a minimum energy path for micro-cracks to propagate, promoting a predominant transgranular failure. Upon intersection with another shear band, the advancing crack tip alternate from a less critical localization condition to a more critical one, as it requires lesser energy for the creation of new fracture surfaces while sustaining the imposed plastic deformation. Grains with Cube or near Cube texture are rather resistant to shear banding and crack propagation whereas the contrary is true for grains with near S and near Goss orientations. It is also shown that the ductile clad layers within the composite AA6016X alloy act as an efficient barrier against the development and propagation of shear bands within the less ductile inner core, thereby significantly enhancing the bendability of the alloy. Through a systematic study, it is further shown that the bendability of AA6016 alloy can be improved significantly through proper engineering of the microstructure.
... As bendability of aluminum alloys is limited by surface induced cracking, the addition of a ductile clad layer at the surface has the potential of improving bendability of age-hardenable aluminum alloys. Recently, few studies have employed a newly developed fusion technology to produce clad material by direct chill (DC) casting [33][34][35]. Jin et al. [34] studied the bendability of AA2124 sheets, cladded with lower strength and higher ductility AA1200, produced via direct chill casting fusion technology. It is reported that the more ductile clad layer, which has a comparatively higher fracture strain, delays the onset of surface cracking during bending, thereby achieving higher bend angles prior to failure. ...
... The authors suggested that the clad alloy releases strain by necking when a crack is initiated, usually near the clad-core interface, and further assists in blunting the crack tip, thus preventing the crack from quickly propagating to the outer bent surface. Lloyd et al. [33] studied the tensile and bending response of AA6111 sheets cladded with up to100μm layers of AA3003 using direct chill casting and the authors reported a significant improvement in bendability. The authors observed that crack initiates from within the lower bendability AA6111 core and eventually propagates through the more ductile cladding, leading to final failure. ...
... Roll bonding is a well-developed process, but its application is limited due to fewer possible combinations of aluminum alloys that can be roll bonded effectively. Aluminum alloys with high Mg content such as the AA5xxx alloys are not easily bondable due to their high vulnerability to oxidation during the roll bonding process, which is typically conducted at elevated temperatures [33]. Furthermore, little to no information is found in literature on the bendability and deformation behavior of AA6xxx series cladded aluminum sheets processed using thermomechanical roll bonding. ...
Article
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In this study, the bendability of two 1 mm thick sheets of monolithic AA6016 and composite AA6016X alloys is investigated using a series of wrap-bend tests, with emphasis on understanding the relationship between microstructure, the nature of plastic deformation and fracture behavior. The composite AA6016X alloy consists of a central core of AA6016 sandwiched between 100 μm thick clad layers of AA8xxx series aluminum alloy, processed using thermomechanical roll-bonding. It is shown that the bendability of monolithic AA6016 alloy is limited due to the formation of severe surface undulations and surface cracking, which is associated with the heterogenous nature of slip that concentrates into 5° - 15° misoriented coarse slip bands of very high dislocation content in the order of 10^14/m^2, and intense shear bands originating from surface low cusps in the form of mutually orthogonal transgranular bands. The micro-cracks initiate at the surface and propagate along these intensely sheared regions, primarily consisting of grains with near S texture component. Grain boundary decohesion occurs along boundaries that are highly misoriented with misorientations ranging from 40˚ up to as high as 60˚, further assisting crack propagation. The composite AA6016X alloy exhibits unlimited bendability with no signs of fracture even after a maximum bend angle of 180°. The extremely high bending strains in AA6016X are accommodated in a homogeneous manner through a grain subdivision process within the AA8xxx clad layers, promoting the formation of deformation induced high angle boundaries. This homogeneous accommodation of strain within the clad layers reduces surface roughness and further enhances the bendability of the alloy.
... Amidst, the Al/Al bimetallic composites may be a promising solution for the automotive and aerospace industries due to the outstanding performances of the aluminium alloys [13][14][15]. There are a large number of methods to prepare the Al/Al bimetallic composites, such as overcasting [16], sequential casting [17], high-pressure die casting [18], direct chill casting [19], compound casting [20], friction stir welding [21], and laser welding [22]. In general, most of the casting methods usually employ a solid-liquid compound manner to fabricate the Al/Al bimetallic composites. ...
Article
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A novel method named the lost foam casting (LFC) liquid–liquid compound process with a Zn interlayer was proposed to prepare the Al/Al bimetallic composites, and the microstructure of the Al/Al bimetallic composites was investigated in the present work. The results showed that the Al/Al bimetallic composites were successfully produced using the novel process. The Zn interlayer prevented different liquid metals from directly mixing. A uniform and compact metallurgical interface was obtained between the Al and the A356 aluminium alloy, which consisted of the η-Zn, α-Al rich, α + η eutectoid, and primary silicon phases. The microhardness of the interface layer was significantly higher in comparison with those of the Al and A356 matrixes.
... While the segregation of Ni element is not observed in squeeze casting, fine and dispersed secondary phase forms in the interfacial region, indicating that the applied pressure refines the microstructure during overcasting process. [40,41] According to the Clausius-Clapeyron, ...
Article
The influence of the coating materials, coating thickness, and casting process on the interfacial microstructure and mechanical properties of the overcast A6061 bars with aluminum A356 and A6061 alloys was studied by OM, SEM/EDS, and mechanical testing. Results indicate that Ni coating has better thermal stability than Cu coating that heavily reacts with liquid Al alloy and forms a reaction zone around 130–150 μm during gravity casting. In the gravity casting, coarse and cracked Al3Ni phase distributes along the interfacial region and degrades the mechanical properties of the overcast joints. In squeeze casting, however, fine and dispersed Ni-rich strengthening phases form uniformly in the interfacial zone and improve the metallurgical bonding of the joints. The heat transition and application of pressure during solidification are two key factors in determining the integrity and mechanical properties of the overcast joints.
... Based on their study, C = 50 when neutral axis remains at the center of the sheet and C = 60 when neutral axis moves. Other studies are also shown general agreement of the bendability with the aforementioned empirical expression, but when C = 70 [118,119]. This constant parameter "C" could vary alloy to alloy i.e., a rough estimation to use constant parameter for every material. ...
Thesis
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Accurate numerical prediction of localization and fracture phenomena during sheet metal forming operations still represents one of the biggest challenges faced by the research community in this field. This is on the one hand due to the experimental difficulty in precisely measuring the stress/strain states at fracture, and on the other due to the numerous concurring mechanisms playing a role on the onset of fracture. This fact often leads to distinct modeling approaches (e.g. for fracture due to the membrane instability or bending cracks), which are able of predicting particular failure types but fall short from delivering a comprehensive understanding of the phenomena. This fact is particularly well evidenced by the recently introduced layered aluminum composites, so-called multilayer Fusion material. These, in fact, behave identically to their main component under membrane loading, but they deliver increased fracture resistance under bending dominant conditions. The state of the art fracture models are unable of predicting this kind of dual behavior. The main objective of this thesis is to describe a unified fracture modeling approach, able to predict fracture for both membrane and bending loading conditions even for complex materials such as layered aluminum composites. The fracture limits are evaluated using a newly proposed measurement technique based on optical microscopy, so-called thinning method, which enables the reliable measurement of fracture strains in Nakazima experiments. These data are combined with the cup-drawing experiment to cover the range of fracture states outside the Nakazima experiments. Different fracture criteria are then employed to extrapolate fracture limit beyond experimental results. These models have been tested against a new triangular deep drawing experiment for both monolithic and layered composites, obtaining high prediction quality in both cases. Substantial role of these fracture models in predicting the region of the crack as well as the time of appearing the fracture is discussed.
... NOVELIS Inc. recently developed and patented a unique variant of the Direct Chill (DC) casting process whereby two different alloys can be cast simultaneously, producing a laminate (or composite) aluminum ingot. Based on information provided in the patent, [1] and in subsequent studies, [2][3][4] many core/clad combinations can be successfully cast utilizing this process. Of particular interest are the AA3xxx-core/AA4xxx-clad ingots. ...
... Lloyd et al. [2] studied the deformation of clad aluminum sheet produced via Fusionä casting. Compound tensile test coupons were fabricated such that the tensile axis was perpendicular to the interface of an AA3003/ 9609 Fusionä ingot; however, as-cast samples were not included in the test. ...
Article
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To improve casting and product yields of Fusion™ cast AA3003-core/AA4045-clad laminate ingots, a fundamental understanding of the wetting and interface formation process between the oxidized AA3003 cast surface and the AA4045 melt is required. In this study, a laboratory scale analog/immersion test was developed which mimics the wetting and interface formation process that occurs during Fusion™ casting. The effects of reheating and remelting of the AA3003 cast surface, the degree of surface oxidation present during initial contact of the two alloys, and the atmospheric conditions (air or argon) on interface formation when dipped into an AA4045 melt were examined. Results indicated that in an argon atmosphere, wetting and dissolution of the solid, oxidized AA3003 samples by liquid AA4045 occurred at temperatures both above and below the measured onset of AA3003 remelting. AA3003/AA4045 interfaces were similar to those produced during Fusion™ casting, with a thin layer of AA4045 forming an oxide-free, metallurgical interface to the AA3003 after immersion. The AA3003 surface oxides were not an impediment to wetting and bond formation. Mg surface segregation was observed on the oxidized AA3003 surfaces and may play a role to help penetrate the oxide layer. For tests conducted in air, wetting of the sample by AA4045 liquid was generally poor regardless of temperature. © 2015 The Minerals, Metals & Materials Society and ASM International