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。

SiC_P/Al-Cu复合材料的高温热变形行为

利用Gleeble-1500D热模拟试验机对SiC_p/Al-Cu复合材料进行压缩实验,研究其在温度为350~500℃、应变速率为0.01~10s-1条件下的高温塑性变形行为。由实验得出变形过程中的应力-应变曲线,建立了热变形本构方程和加工图。结果表明:复合材料高温流动应力-应变曲线主要以动态再结晶为特征,峰值应力随变形温度的降低或应变速率的升高而增加。其热压缩变形时的流变应力可采用Zener-Hollomon参数的双曲正弦形式来描述,在实验条件下平均热变形激活能Q为320.79kJ/mol。确定了加工图中的稳定区和失稳区,分析了加工图中不同区域的显微组织结构,失稳区存在颗粒破裂、孔洞等。

原位反应Al-Cu复合材料的反应机理分析

借助X射线衍射和扫描电镜对铝熔体中生成Al2 O3的原位反应进行热力学和动力学分析 结果表明 :在大气、低温条件下 ,CuO与铝反应能生成δ Al2 O3,δ Al2 O3颗粒在基体合金中能均匀分布 ,大小在 3～ 5 μm ;CuO与铝反应的热力学分析认为反应是可以自发进行的 ;利用宏观反应动力学理论 ,提出微粒模型 ,认为主要影响反应速度的因素是铝液与CuO微粒接触时的浓度、微粒的内部结构、表面积与其体积之比。

低压铸造-轧制法快速制备Al-Cu复合材料

采用低压铸造-轧制法实现了快速制备650 mm×30 mm×7 mm×R3.5 mm的 Al/Cu 复合材料,并通过 SEM、EDS、XRD和电子万能试验机（AG-X）表征其结构和界面剪切强度。结果表明：在Cu管预热温度200℃,轧制压下率30%,冷却水通量400 L/h,Al液温度680～740℃条件下均可实现 Al-Cu之间的冶金结合,界面合金层随着 Al液温度的升高而变宽；复合材料的导电性能和界面结合剪切强度受界面金属间化合物层宽度的影响,其宽度越宽,剪切强度降低。低压铸造法制备 Al-Cu复合材料工艺流程短,一次成形快,并能对界面物相进行有效调控。

SiC_P/Al-Cu复合材料动态再结晶行为及临界条件

利用Gleeble-1500D热模拟试验机对40%SiC_P/Al-Cu复合材料进行压缩实验,研究其在温度为350~500℃、应变速率为0.01~10 s^(-1)条件下的高温塑性变形行为。由实验得出变形过程中的应力-应变曲线,采用加工硬化率处理方法对应力-应变数据进行处理,结合lnθ-ε曲线的拐点和(-α(lnθ)/αε)-ε曲线最小值的判据,研究该复合材料动态再结晶临界条件。结果表明:40%SiC_P/Al-Cu复合材料的应力-应变曲线主要以动态再结晶软化机制为特征,峰值应力(σ_p)随变形温度的降低或应变速率的升高而增加;该材料的lnθ-ε曲线出现拐点,(-α(lnθ)/αε)-ε曲线出现最小值;临界应变(ε_c)随变形温度的升高与应变速率的降低而减小,且临界应变与峰值应变(εp)之间具有相关性,即ε_c=0.528εp;临界应变与Zener-Hollomon参数(Z)之间的函数关系为ε_c=4.58×10^(-3)Z^(0.09)。透射电镜观察显示应变为0.06时(变形温度为400℃,应变速率为10 s^(-1))已经发生动态再结晶,应变为0.2时,动态再结晶晶粒充分长大。

Al_2O_(3P)/Al-Cu复合材料的二次加热组织演变

采用原位反应近液相线铸造方法制备Al2O3P/Al-Cu复合材料,对其进行二次加热,研究晶粒的形貌演变和长大规律。用光学显微镜观察组织结构,应用Image Pro Plus软件测量并统计出平均晶粒尺寸及合金液相体积分数,并与理论计算数值进行比较。结果表明,在590℃保温10～60 min后,不含Al2O3颗粒的Al-6.8%Cu基体合金平均晶粒尺寸为89～132μm,液相体积分数为14%～26.8%,而3.6 wt%Al2O3P/Al-6.8%Cu复合材料的平均晶粒尺寸为73-107μm,液相体积分数为11.6%～20.9%。说明Al2O3颗粒在合金的二次加热过程中对晶粒长大行为及液相体积分数的增长均有明显的抑制作用,从而为优化半固态组织提供了一种新思路。

热处理对热等静压Si_P/Al-Cu复合材料显微组织和力学性能的影响

采用元素粉作为原料,通过热等静压技术(HIP)制备出50%SiP/Al-Cu和70%SiP/Al-Cu(体积分数)复合材料,研究固溶处理和峰值时效处理对复合材料显微组织、Al2Cu相溶解过程及力学性能的影响。结果表明:热等静压技术制备的SiP/Al-Cu复合材料完全致密,组织均匀细小,材料由Si相、Al相和Al2Cu组成,白色Al2Cu相产生于原始的Cu粉与Al粉界面处。在516℃固溶处理2h后,70%SiP/Al-Cu复合材料中的Al2Cu相全部溶入Al基体中,而50%SiP/Al-Cu复合材料中还残留少量Al2Cu相。经过峰值时效处理后,50%SiP/Al-Cu和70%SiP/Al-Cu复合材料的抗弯强度为548MPa和404MPa,相对于热等静压态分别提高了38.81%和13.51%,复合材料的强度显著增强。

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%。

C/Al-40%Cu复合材料的原位热解-热压法制备及微观结构

以聚乙烯醇缩丁醛为碳源,采用原位热解-热压法制备C/Al-40%Cu(体积分数)复合材料,研究了该复合材料的物相组成、微观结构以及界面反应特性。结果表明:复合材料主要由铝相、铜相、原位生成的碳材料以及少量残留的高分子材料组成,碳材料连续存在于铝、铜相颗粒之间,有效抑制了Al2Cu和Al4Cu9等金属间化合物的生成;复合材料的实测密度接近于理论密度,组织中未见明显孔洞,致密程度较高;复合材料界面结合良好,铝相和铜相、铝相和碳材料层之间均发生了元素互扩散,形成了厚度分别为2.0~3.5μm和1.0~1.5μm的扩散层,铜相和碳材料层之间以机械结合方式连接。

原位Al_2O_3颗粒对近液相线铸造Al-Cu合金二次加热组织的影响

采用原位反应近液相线铸造方法制备Al2O3p/Al-Cu基复合材料,对其进行二次加热,研究晶粒的形貌演变和长大规律。用光学显微镜观察组织、I mage Tool软件测量平均晶粒尺寸、I mage pro plus软件测量合金液相率,并与理论计算数值比较。结果表明,在590℃保温10、20、40、60 min后,Al2O3p/Al-Cu基复合材料的平均晶粒尺寸比不含Al2O3颗粒的基体合金减少15～25μm,液相率依次为11.6%、13.2%、15.3%、20.9%,较基体合金的液相率小且增长速度慢。说明Al2O3在合金的二次加热过程中对晶粒长大行为具有明显的抑制作用,从而为优化半固态组织提供了一种新思路。

车用碳纤维增强Al-Cu基复合材料的微观组织及力学性能研究

采用真空压力渗透法制得Cu电镀液涂覆处理后的碳纤维(CF)增强Al-Cu基复合材料,进行力学性能测试并观察其显微组织。结果表明:对碳纤维表面进行镀Cu处理后形成了具有致密组织、厚度约1μm的界面层,界面层与碳纤维之间形成了紧密结合状态。碳纤维和Al-Cu基体之间形成了良好结合,未发现与Al-Cu基体呈分离状态的碳纤维束。碳纤维已被Al-Cu液充分渗透,未发现有孔隙出现。相对于Al-Cu基体,复合材料内除包含C与Al之外,还存在Al2Cu金属间化合物。相比Al-Cu基体,CF/Al-Cu基复合材料试样的抗拉强度得到明显提高。在断裂阶段碳纤维束内形成了许多微裂纹,此时形成了阶梯状的断口,并且断口部位也具有平整的结构。

Hot deformation and processing maps of as-sintered CNT/Al-Cu composites fabricated by flake powder metallurgy

The deformation behaviors of as-sintered CNT/Al-Cu composites were investigated by isothermal compression tests performed in the temperature range of 300-550°C and strain rate range of 0.001-10 s-1 with Gleeble 3500 thermal simulator system.Processing maps based on dynamic material model(DMM)were established at strains of 0.1-0.6,and microstructures before and after hot deformation were characterized by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and high-resolution transmission electron microscopy(HRTEM).The results show that the strain has a significant influence on the processing maps,and the optimum processing domains are at temperatures of 375-425°C with strain rates of 0.4-10 s-1 and at 525-550°C with 0.02-10 s-1 when the strain is 0.6.An inhomogeneous distribution of large particles,as well as a high density of tangled dislocations,dislocation walls,and some sub-grains appears at low deformation temperatures and strain rates,which correspond to the instability domain.A homogeneous distribution of fine particles and dynamic recrystallization generates when the composites are deformed at 400 and 550°C under a strain rate of 10 s-1,which correspond to the stability domains.

Simulation and experimental verification of interfacial interactions in compound squeeze cast Al/Al-Cu macrocomposite bimetal

The objective of this work was to investigate the thermal and mechanical interactions between the two components of a compound squeeze cast macrocomposite bimetal. First, an Al/Al-4.5wt.%Cu macrocomposite bimetal was fabricated by compound squeeze casting process. Then, heat transfer, solidification and distribution of the generated stresses along the interface region of the bimetal were analyzed using Thermo-Calc, ProCAST and ANSYS softwares, and structure, copper distribution and microhardness changes across the interface of the bimetal were studied. The results showed no noticeable change in the structure of the Al-4.5wt.%Cu insert and no obvious micromixing and diffusion of copper across the interface. Simulation results were in good agreement with the experimental ones only when an equivalent oxide layer at the interface was defined and its effect on heat transfer was considered. This layer caused up to 50% decrease in local liquid fraction formed on the surface of the insert. Simulation of the generated stresses showed a uniformly distributed stress along the interface which was significantly lower than the compressive strength of the oxide layer, resulting in its good stability during the fabrication process. It was postulated that this continuous oxide layer not only acted as a thermal barrier but prevented the direct metal-metal contact along the interface as well.

Effects of Cu content on microstructures and compressive mechanical properties of CNTs/Al-Cu composites

The carbon nanotubes(CNTs) reinforced Al-Cu matrix composites were prepared by hot pressing sintering and hot rolling, and the effects of Cu content on the interfacial reaction between Al and CNTs, the precipitation behavior of Cu-containing precipitates, and the resultant mechanical properties of the composites were systematically investigated. The results showed that the increase of Cu content can not only increase the number and size of Cu-containing precipitate generated during the composite fabrication processes, but also promote the interfacial reaction between CNTs and Al matrix, leading to the intensified conversion of CNTs into Al_(4)C_(3). As a result, the composite containing 1 wt.% Cu possesses the highest strength, elastic modulus and hardness among all composites, due to the maintenance of the original structure of CNTs. Moreover, the increase of Cu content can change the dominant strengthening mechanisms for the enhanced strength of the fabricated composites.

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.

Wetting of molten Sn-3.5Ag-0.5Cu on Ni-P(-SiC) coatings deposited on high volume faction SiC/Al composite

The wetting of molten Sn-3.5Ag-0.5Cu alloy on the Ni-P(-SiC)coated SiCp/Al substrates was investigated by electroless Ni plating process,and the microstructures of the coating and the interfacial behavior of wetting systems were analyzed.The SiC particles are evenly distributed in the coating and enveloped with Ni.No reaction layer is observed at the coating/SiCp/Al composite interfaces.The contact angle increases from^19°with the Ni-P coating to 29°,43°and 113°with the corresponding Ni-P-3SiC,Ni-P-6SiC and Ni-P-9SiC coatings,respectively.An interaction layer containing Cu,Ni,Sn and P forms at the Sn-Ag-Cu/Ni-P-(0,3,6)SiC coated SiCp/Al interfaces,and the Cu-Ni-Sn and Ni-Sn-P phases are detected in the interaction layer.Moreover,the molten Sn-Ag-Cu can penetrate into the Ni-P(-SiC)coatings through the Ni-P/SiC interface and dissolve them to contact the SiCp/Al substrate.

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.

原位反应近液相线铸造Al_2O_3/Al-Cu合金的二次加热工艺

采用原位反应近液相线铸造方法制备3.6wt%Al2O3/Al-Cu基复合材料,通过光学显微镜和XRD分析Al2O3/Al-Cu复合材料的显微组织,研究半固态Al2O3/Al-Cu复合材料的二次加热工艺。结果表明,随着二次加热温度的升高和保温时间的延长,晶粒组织的球化和粗化过程同时进行,在590～600℃区间,保温20～40 min的晶粒组织的圆度及平均晶粒尺寸较为理想。