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.

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.

Microstructure and mechanical behavior of Ti/Cu/Ti laminated composites produced by corrugated and flat rolling

Ti/Cu/Ti laminated composites were fabricated by corrugated rolling(CR) and flat rolling(FR) method.Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron microscopy, numerical simulation methods, peel and tensile examinations. The effect of CR and FR was comparatively analyzed. The results showed that the CR and FR laminated composites exhibited different effective plastic strain distributions of the Ti layer and Cu layer at the interface. The recrystallization texture, prismatic texture and pyramidal texture were developed in the Ti layer by CR, while the R-Goss texture and shear texture were developed in the Cu layer by CR. The typical deformation texture components were developed in the Ti layer and Cu layer of FR laminated composites. The CR laminated composites had higher bond strength, tensile strength and ductility.

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。

微量Sm元素对TiC_(p)/Al-Cu-Mg-Mn复合材料微观组织和力学性能的影响

以0.27%(体积分数)TiC颗粒增强的TiC_(p)/Al-5Cu-1.9Mg-0.9Mn复合材料为基体,研究不同Sm元素含量对复合材料组织与力学性能的影响规律。结果表明:Sm元素的加入明显细化了枝晶组织,促进了固溶处理过程中第二相的溶解,使得时效态组织中T-Al_(2)0Cu_(2)Mn_(3)和S′-Al_(2)CuMg析出相的数量密度增加,当Sm元素含量较高时(0.3%,质量分数,下同),组织中将出现块状难溶稀土化合物。随着Sm的加入,复合材料室温和250℃下的屈服强度逐渐增加,但会引起塑性降低,当Sm元素添加量为0.3%时,室温屈服强度从246 MPa提高到310 MPa,250℃屈服强度从191 MPa提高到220 MPa。分析认为,强度提高源于Sm引起的组织细化和析出相数量密度增加,而塑性下降是由于粗大块状难溶稀土化合物割裂了基体,导致裂纹源容易产生。

Cu-Sn、Ni-Cr、Co烧结助剂对Ni_(3)Al基金刚石复合材料性能的影响

采用真空热压法制备了Ni_(3)Al基金刚石复合材料,研究了不同烧结助剂对复合材料力学性能和微观结构的影响,并对Ni_(3)Al基金刚石钻头的钻孔性能进行了测试。结果表明,在添加0~30vol%的Cu-Sn、Ni-Cr、Co烧结助剂后,Ni_(3)Al基金刚石刀头的致密度、抗弯强度、硬度得到提高。Ni3Al基金刚石复合材料的抗弯强度随着Ni-Cr、Co烧结助剂含量的增加而提高。Cu-Sn、Ni-Cr烧结助剂中的Cr元素在金刚石的表面出现了富集现象。将添加Cu-Sn、Ni-Cr烧结助剂的Ni_(3)Al基金刚石复合材料制备成工具进行钻削测试,发现Ni_(3)Al基金刚石复合材料的失效形式可以分为微破碎、磨耗、宏观破碎3种形式,钻削试验中并没有发现整颗金刚石脱落的现象,表明Ni_(3)Al基对金刚石的把持力较大,强度较高。

添加明胶优化仿贝壳TiB2/Al-Cu复合材料的组织和力学性能

采用冷冻铸造及压力浸渗制备了TiB_(2)/Al-Cu层状复合材料。研究了明胶含量对复合材料组织和力学性能的影响。同时,分析了其组织、断裂和磨损机理。结果表明,随着明胶添加量的增加,TiB_(2)/Al-Cu复合材料的抗压、抗弯强度和韧性均有所提高。当明胶含量为1.0 wt%时,复合材料具有最佳的力学性能,其抗压强度、抗弯强度、裂纹萌生韧性(KIC)和裂纹扩展韧性(KJC)分别为(625±13)MPa,(626±4)MPa,(22.23±0.2)MPa·m^(1/2)和(54.43±2.4)MPa·m^(1/2)。此外,明胶的加入提高了TiB_(2)/Al-Cu层状复合材料的耐磨性能。力学性能和耐磨性能提高均归因于添加明胶后,陶瓷片层开始弯曲且桥接增多,TiB_(2)/Al-Cu层状复合材料微观结构得到优化。当复合材料受到外部载荷时,增加了形成多裂纹可能性,同时弯曲的陶瓷片层和陶瓷桥接有效地阻碍了金属片层间的剪切流动并抑制了金属的塑性变形,最终提高了复合材料的性能。

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.

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.

5 mass%TiB_(2)/Al-4.5Cu-xSc-yZr复合材料的微观组织和力学性能

颗粒增强铝基复合材料的室温韧性和高温强度是制约其应用的主要瓶颈,寻求时效析出相的高温稳定和促进增强颗粒的均匀分布是同步解决该问题的潜在途径之一。采用对掺熔盐反应法原位制备了5 mass%TiB_(2)/Al-4.5Cu-xSc-yZr复合材料,研究了微量添加Sc、Zr元素对TiB_(2)/Al-4.5Cu复合材料微观组织和力学性能的影响。结果表明:Sc和Zr元素的联合添加既能促进TiB_(2)的均匀分布又能明显抑制铸造缺陷,多级热处理工艺进一步促进了θ′-Al_(2)Cu和Al_(3)(Sc,Zr)相的稳定析出,所制备的5 mass%TiB_(2)/Al-4.5Cu-0.2Sc-0.2Zr复合材料的室温抗拉强度达到了385.1 MPa,断裂伸长率为8.6%,300℃下,抗拉强度达到了167.6 MPa,断裂伸长率为9.3%。

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.

T6态CNTs/Al-Zn-Mg-Cu复合材料的耐磨性能研究

采用熔融铸造法制备了12vol%CNTs(碳纳米管)/Al-Zn-Mg-Cu复合材料,再对该复合材料进行T6热处理。利用MG-200型摩擦磨损试验机研究了热处理前后CNTs/Al-Zn-Mg-Cu复合材料的干滑动摩擦磨损性能。试验结果表明:CNTs对Al-Zn-Mg-Cu合金有细晶强化作用,提高了合金的硬度,固溶处理消除了铸造复合材料中的第二相偏析,并且在时效处理之后MgZn2强化相的析出大幅度提升了材料的性能。在40 N的载荷和200 r/min转速时,T6态CNTs/Al-Zn-Mg-Cu复合材料的磨损率和摩擦系数分别为0.0489 g/mm和0.281,与铸造复合材料相比,材料的磨损率和摩擦系数分别降低64.79%和28.47%。这是由于热处理之后试样的强度和硬度增大,从而有效改善了材料的耐磨性能。未热处理的复合材料主要存在黏着磨损和磨粒磨损,而热处理之后复合材料的主要磨损机理为磨粒磨损。

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.

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.

波纹轧制制备Cu/Al复合板的应力分析及显微组织演变

建立三维有限元模型,并通过50%压下量的轧制试验验证模型的准确性。从时间角度分析整个波纹轧制过程中金属的流动规律。金属经历的变形可以分为两个阶段:填充阶段和压下阶段。填充阶段应力变化较为复杂,而压下阶段应力变化趋势一致。通过罗德参数和应力三轴度分析特征位置的应力状态,在开始变形时为两向拉应力一向压应力。采用EBSD技术分析Cu板的显微组织演变过程。与原始板材相比,铜板各特征位置晶粒均发生细化,而Cu板波谷处晶粒在发生细化后有长大的现象,这是由剧烈塑性变形产生的绝热温升现象造成的。