SiC_p尺寸及基体强度对铝基复合材料破坏机制的影响

EFFECTS OF PARTICLE SIZE AND MATRIX STRENGTH ON THE FAILURE MECHANISM OF SiC_p REINFORCED ALUMINIUM MATRIX COMPOSITES

对粉末冶金法制备的尺寸分别为3．5，10，20μm的Sicp增强Al-Cu基复合材料的拉伸断口及EDX成分分析表明，增强相尺寸大于10μm时，复合材料的破坏归因于SiCp解理形成的裂纹；增强相尺寸为3．5μm时，复合材料的破坏则归因为SiC-Al界面撕裂形成空洞和裂纹.拉伸试验表明，小尺寸SiCp增强的复合材料具有高的拉伸强度及延伸率.低强度复合材料由于基体强度降低，塑性增加，破坏过程主要表现在拉伸载荷下SiCp附近铝基体的空洞形核、长大和聚合.

Three different sizes(3.5, 10, 20μm) of SiC particulate and Al-Cu alloy powder were employed to fabricate composites via powder metallurgy technique. The fracture surfaces of the tensile specimen and EDX analysis show that the reinforcement size has a prominent effect on the failure mechanism of the composites. When the reinforcement size exceeds 10 μm, the failure of the MMC results from the SiC.cleavage crack.The breakage is due to the cavity and micro-crack formed by Al-SiC interfacial tearing,however,when the reinforcement size is 3.5 μm. The Al tearing ridge on the SiCp. surface is similar to the conglutination of Al by pulling-out of whisker in SiCw/Al. The tensile test result shows that the MMCs reinforced with small size of particulate has an elevated ultimate tensile strength and elongation. The low strength MMCs, due to their lower matrix strength, has increased plastics and their failure under tensile load is dominated by cavity nucleation, growth and coalescence nearby the SiCp.