Microstructural development and its effects on mechanical properties of Al/Cu laminated composite

The microstructural development and its effect on the mechanical properties of Al/Cu laminated composite produced by asymmetrical roll bonding and annealing were studied. The composite characterizations were conducted by transmission electron microscope（TEM）, scanning electron microscope（SEM）, peeling tests and tensile tests. It is found that the ultra-fine grained laminated composites with tight bonding interface are prepared by the roll bonding technique. The annealing prompts the atomic diffusion in the interface between dissimilar matrixes, and even causes the formation of intermetallic compounds. The interfacial bonding strength increases to the maximum value owing to the interfacial solution strengthening at 300 °C annealing, but sharply decreases by the damage effect of intermetallic compounds at elevated temperatures. The composites obtain high tensile strength due to the Al crystallization grains and Cu twins at 300 °C. At 350 °C annealing, however, the composites get high elongation by the interfacial interlayer with submicron thickness.

Morphology and Frictional Characteristics Under Electrical Currents of Al_2O_3/Cu Composites Prepared by Internal Oxidation

Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.

Microstructure,Corrosion and Mechanical Properties of Medium-Thick 6061-T6 Alloy/T2 Pure Cu Dissimilar Joints Produced by Double Side Friction Stir Z Shape Lap-Butt Welding

A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.

Microstructure and mechanical properties of Al/Cu/Mg laminated composite sheets produced by the ARB proces

In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding(ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.

Effects of intermediate Ni layer on mechanical properties of Al–Cu layered composites fabricated through cold roll bonding

Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature(either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3 vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.

Improvement of the matrix and the interface quality of a Cu/Al composite by the MARB process

The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.

Reaction thermodynamics and kinetics on in situ Al_2O_3/Cu composites

The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.

Aging behavior of Al_2O_3 short fiber reinforced Al-Cu alloy composites

Al2O3 short fiber reinforced Al-Cu composites containing 1%, 3%, 5% and 7% Cu were fabricated by a squeeze casting technique. The as-cast Al2O3/Al-Cu composites were solution treated at 535 ℃ and then aged at 170, 190 and 210 ℃, respectively. Age hardening behavior of the Al2O3/Al-Cu composites was analyzed by measuring the hardness of the samples at different aging temperatures and aging time. Microstructures of the composites were observed by transmission electron microscope(TEM). The results indicate that the hardness of the Al2O3/Al-Cu composites containing 7% Cu is much higher than that containing 1%-5% Cu because of the large amount of CuAl2 precipitant in the Al2O3/Al-Cu composite. With the increase of Cu content from 1% to 7%, the time needed for the appearance of peak hardness shortened, indicating that the addition of Cu can accelerate the kinetic of CuAl2 precipitation in the Al2O3/Al-Cu composites. The Al2O3/Al-Cu composite containing 7% Cu shows the highest increment of hardness by aging treatment. Therefore, in order to get a higher peak hardness, the Al2O3/Al-Cu composites need more Cu addition as compared with the un-reinforced Al-Cu alloys.

Formation and growth of Cu-Al IMCs and their effect on electrical property of electroplated Cu/Al laminar composites

Cu/Al laminar composite was prepared by dipping Zn layer and then electroplating Cu thick layer on pure Al sheet.During annealing the Cu/Al composites at temperature from 473 to 673 K, the Cu/Al interfacial diffusion and reaction and itskinetics and also the electrical resistivity of the composites were studied. The results show that no Cu?Al IMC layer is observable asthe composites are annealed at 473 K for time till 360 h, indicating that the Zn intermediate layer can effectively suppress the Cu/Alinterfacial diffusion. However, as the composites are annealed at 573 K and above, Zn atoms in the Zn layer dissolve into the Culayer. Tri-layered reaction product of CuAl2/CuAl/Cu9Al4 then forms from the Al side to the Cu side. The IMC layer follows thediffusion-controlled growth kinetics. Electrical resistivity of the Cu/Al composites increases with the increase of the annealingtemperature and time.

RELATIONS BETWEEN INTERFACE OF CF/Al-4.5 Cu COMPOSITE AND SOLIDIFICATION PROCESSING

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High Temperature Flow Stress Prediction of Nano-Al_2O_3/Cu Composite Using an Artificial Neural Network

Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt （L-M） algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500℃ to 850 ~C. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.

High Temperature Deformation of Al_2O_3/Cu Composites

This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.

Interface characterization of Al/Cu 2-ply composites under various loading conditions

The effects of reduction ratio during roll bonding on the microstructural evolution at interface and subsequent mechanical properties of roll-bonded Al/Cu 2-ply sheets were investigated. The interface microstructures for several Al/Cu 2-ply sheets fabricated under different reduction ratios between 30% and 65% were verified by transmission electron microscopy(TEM). Taking the difference of interface microstructure into consideration, 3-point bending and peel tests were performed for obtaining flexural and bonding strengths for Al/Cu 2-ply sheets. The effect of the quantified areas of metallurgical bonding at interfaces on the bonding strength was also discussed. The results show that both the bonding and flexural strengths for Al/Cu 2-ply sheets are reduced by decreasing the reduction ratio during the roll bonding process, which is strongly correlated with the interface microstructure. This was especially verified by observing the interface delamination from the 3-point bent samples.

An investigation on mechanical properties of (Al_(63)Cu_(25)Fe_(12))p/ZL101 composites by squeeze casting

Influence of different extrusion pressures and pouring temperatures on comprehensive performance of(Al63Cu25Fe12)p/ZL101 composites is studied in this paper.The results show that the tensile strength,elongation and hardness of(Al63Cu25Fe12)p/ZL101 composite increase with the squeezing pressure increasing from 50 MPa to 100 MPa,and gradually reduce from 100 MPa to 150 MPa.In addition,the mechanical properties of the composite can be improved with pouring temperature growing,while the temperature should not exceed 760℃.When squeezing pressure is 100 MPa and pouring temperature is 720℃,mechanical properties of composites are the best.Finally,the mechanical properties of(Al 63 Cu 25 Fe 12)p/ZL101 composite will be improved by suitable heat treatment technology

Microstructure and Mechanical Property of in-situ Al-Cu/TiC Composites

An approach named direct reaction synthesis (DRS) has been developed to fabricate particulate composites with an extremely fine reinforcement size. ID situ Al matrix composites were fabri-cated by DRS. Extensive analysis of the composites microstructure using SEM and TEM identify that the reinforcement formed during the DRS process is Ti carbide (TiC) particle, generally less than 1.0 μm. The reacted, semisolid extruded samples exhibit a homogeneous distribution of fine TiC particles in Al-Cu matrix, Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure although the ductility and strength are limited by the presence of coarse titanium aluminides (Al3Ti).

Effect of Mg Addition on the Structure and Properties of Al-4.5 Cu-3.4 Fe <i>In-Situ</i>Cast Composite

Ternary Al-4.5 (wt%) Cu-3.4 (wt%) Fe in-situ composite was prepared at 1100&#176;C by conventional casting method. However, this particular alloy contains larger needle-shaped intermetallics of Al3Fe phase. These exert adverse effect on the mechanical properties of the alloys. The larger shape and uneven orientation of the intermetallic were found to be responsible for the degradation of properties. The main purpose of this study was to modify the geometry of those needles by adding magnesium (Mg) as a fourth material. A series of alloys were prepared by adding 4, 6, 8, 10, wt% Mg in Al-4.5 (wt%) Cu-3.4 (wt%) Fe alloy. Microstructures were observed by optical microscopy. Mechanical properties like ultimate tensile strength, % elongation, % area reduction, hardness and wear test were determined. The study revealed that Mg transformed the needles of Al3Fe into globular shape which gave the alloys better mechanical properties.

Changes in the Structure and Properties of the Cu-Pb Composites Interface Jointed in the Solid Phase

Research of structure and properties of Cu-Pb-Cu composite interface, obtained by technology of pack rolling of the pair of mutually insoluble metals, was performed using the methods of metallography, micro- and nano-hardness, mechanical tests, energy-dispersion elementary analyses. The work was aimed at the analyses of possible mechanical mechanisms of mass-transfer, determining the hardness of metal joint in conditions of absence of inter-diffusion. It was shown that different intensity of mass transfer of copper and lead takes place through the composite interface, which corresponds to the results obtained on the other system of dissimilar materials—copper-niobium. Qualitative explanation of these patterns was offered on the basis of more intensive plastic flow of fusible compound of the composite in conditions of roll-bond joining.

Cu-Al层状复合材料金属间化合物结构稳定性的第一性原理计算

铜铝层状复合材料在固液复合铸轧成型时,固态铜与液态铝在接触面发生界面反应生成的金属间化合物容易引发晶界脆性、晶间裂纹或弹性畸变致使其开裂而失效。因此,一个强而稳定的界面对于整个复合材料的结构强度至关重要。为深入了解界面金属间化合物的化学键合、晶体结构及稳定性,利用第一性原理对Cu-Al层状复合材料中常见的金属间化合物Al_(4)Cu_(9)、Al_(2)Cu、AlCu开展了热力学性能、力学性能和电子结构的相关计算。有效生成热数值表明,扩散初始阶段Al_(2)Cu相将在界面处最先生成,待Al_(2)Cu初生相形成后,将依次生成Al_(4)Cu_(9)、AlCu。Al_(2)Cu、Al_(4)Cu_(9)和AlCu均符合力学稳定性标准,对比它们的B/G值、泊松比和硬度,3种金属间化合物均为脆性相,其中Al_(2)Cu的脆性最大且硬度最高。通过对能带、态密度和Mulliken布居进行分析,发现金属键在Al_(2)Cu和AlCu化学键中具有更强的离子性特征,而在Al_(4)Cu_(9)化学键中具有更强的共价性特征,使得Al和Cu原子之间的相互作用更紧密,稳定性更强。

基于分子动力学模拟的Cu-Zr/Al复合材料的变形行为

采用分子动力学模拟方法研究了Zr含量对Cu/Al层状复合材料拉伸变形行为的影响,使用取代掺杂的方式用Zr取代Cu/Al层状复合材料中的Cu,取代比例分别为0.25%、0.45%、0.65%、0.85%和1.05%。结果表明:随着Zr取代比例的增加,Cu-Zr/Al复合材料的极限拉伸强度和最大拉伸应变呈现波动变化的趋势。当Zr的取代比例为0.85%时,复合材料的极限抗拉强度和最大拉伸应变最大,继续增加Zr的含量则会使极限拉伸强度和最大拉伸应变都减小。随着应变的增加,FCC结构、BCC结构以及HCP结构会发生相互转化,沿Y轴进行拉伸时,初始阶段相结构转变更加明显;随着Zr取代比例的增加,塑性变形过程中复合材料的晶型转变将会推迟进行,Shockley不全位错在塑性变形过程中起主导作用,且沿Y轴拉伸时的位错线长度大于沿Z轴拉伸时的位错线长度,同时由于Zr元素的加入,影响位错的扩散,导致复合材料的位错密度降低,从而提高其强度。