【作者】 刘崇宇；

【导师】 刘日平； 马明臻；

【作者基本信息】 燕山大学 ， 材料学， 2013， 博士

【摘要】 本文利用累积叠轧焊法制备铝基复合材料，该方法不同于粉末冶金、气相沉积、搅拌铸造和原位生成等传统制备铝基复合材料的方法，不需要考虑强化相与铝基体的润湿角、熔点差和密度差等问题。同时累积叠轧焊法还是一种大塑性变形方法，利用该种方法在制备颗粒强化铝基复合材料时，也将超细晶组织和大量位错引入到了铝基体中。制备出的铝基复合材料的强化机制不仅有第二相强化，还存在细晶强化和位错强化。利用累积叠轧焊法制备出了WC颗粒强化铝基复合材料，对比超细晶纯铝，该复合材料具有较高的硬度、拉伸强度和耐磨损性能。采用shear lag模型对制备出的Al/WC复合材料的屈服强度进行理论计算，发现计算结果与实验所得结果十分吻合。提出累积叠轧焊法制备的无机非金属颗粒强化铝基复合材料的强化机制有大塑性变形导致的细晶强化和位错强化；第二相颗粒引起的基体热膨胀位错强化、细晶强化、Orowan强化、二次位错强化和GNBs强化。采用累积叠轧焊法制备出了金属W颗粒强化铝基复合材料。电子扫描图片显示该种铝基复合材料的W颗粒均匀地分布在铝基体中；X射线衍射显示复合材料中只有Al和W两相；能谱显示Al基体与W颗粒的界面结合良好。最终制备出的Al/4.2vol%W复合材料的抗拉强度达到160MPa。Al/4.2vol%W复合材料的电阻率为2.77μ·cm，仅比退火态纯铝高出4%左右，金属强化颗粒使得该种铝基复合材料具有优异的导电性能。通过累积叠轧焊法和真空热处理制备出一种由金属间化合物Al3Mg2片段强化的铝基复合材料。随叠轧道次的增加，强化相Al3Mg2在Al基体中分布越来越均匀。Al/Al3Mg2复合材料的抗拉强度与拉伸塑性均随叠轧道次的增加而增加，最终材料的最大抗拉强度达到168MPa。通过累积叠轧焊和真空固溶处理制备出一种新型Al/Zn复合材料，该种复合材料的基体中均匀分布着Al-Zn固溶区域，且Al-Zn固溶区域与纯Al基体区域间无明显界面。显微硬度结果表明Al-Zn固溶区域为Al/Zn复合材料的强化区域。该种复合材料在拉伸的过程中，强化区域随Al基体一同发生塑性变形，传统铝基复合材料拉伸过程中存在的局部应力过大现象可以被消除，同时消除了拉伸裂纹优先成核源和优先扩展路径，进而避免了铝基复合材料的过早拉伸失效。与累积叠轧焊制备的超细晶结构纯Al相比，该种Al基复合材料在不降低塑性的前提下明显地提高了基体材料的抗拉强度。更多还原

【Abstract】 Accumulative roll bonding (ARB) is used as a new method to fabricatealuminium-based metal matrix composites (AMMCs). The ARB method can solve theproblems such as non-uniform distribution, poor wettability of reinforcement, porosity,and poor economical efficiency in the traditional methods. ARB is one of the severeplastic deformation techniques used to fabricate ultrafine-grained materials. So, themechanical properties of AMMCs which fabricated by ARB process is influenced by thehard phase, the boundary hardening and dislocation hardening.Al/WC composites with high hardness, good mechanical properties, and wearresistance were produced by ARB process. The yield strength of the composites wasdetermined by tensile tests and compared with the calculated yield strength. The resultsindicated that there is a good agreement between the calculated yield strength andexperimental value. The strengthening mechanisms of those Al/WC composites areboundary hardening and dislocation hardening which introduced by severe plasticdeformation process and thermal expansion dislocation hardening, small subgrainhardening, Orowan hardening, secondary dislocation hardening, and geometricallynecessary dispersion hardening which introduced by WC phase.AMMCs reinforced with pure W particulates are manufactured through ARB. X-raydiffraction analysis reveals no Al-W intermetallics in the composites. The microstructureof the composites shows excellent W particle distribution in the matrixes. Tensile,hardness, and electrical conductance properties of the composites are determined. Theresults show that the introduction of4.2vol%W particles to Al matrix via ARB processleads to significantly enhanced mechanical properties and excellent electrical conductivity.Al/Al3Mg2composites were produced by ARB and vacuum annealing. Thereinforced phase in the composites is a type of Al-Mg intermetallic compound.Investigations regarding the hardness and tensile properties of the composites showed thatthe Vickers microhardness, tensile strength, and elongation of the Al/Al3Mg2compositesincreased with the number of ARB cycles. Compared with the annealed and ARB monolithic1060-Al, the Al/Al3Mg2composites showed excellent mechanical propertiesand low density.Al/Zn composites were fabricated using1060-Al plates and Zn particles by ARB andheat treatment. X-ray diffraction analysis reveals that most of the Zn phase in the finalAl/Zn composite disappeared in the Al matrix. Scanning electron microscopy andenergy-dispersive X-ray spectroscopy analyses revealed excellent solid solution regionsdistribution in the final Al/Zn composite. The final Al/Zn composite showed higherhardness values of the solid solution regions than the Al matrix. Compared with ARBedmonolithic1060-Al, the Al/Zn composites had higher strength without sacrificingductility.更多还原