搅拌铸造结合搅拌摩擦加工制备不同体积分数SiC_(p)/Al复合材料的摩擦磨损行为

Friction and Wear Behavior of Different Volume Fraction SiC_(p)/Al Composites by Stir Casting Combined with Friction Stir Processing

采用搅拌铸造结合搅拌摩擦加工方法制备了SiC颗粒体积分数分别为20%,25%,30%的SiC_(p)/Al复合材料,研究了复合材料的显微组织和力学性能,并基于市域列车的实际运行工况(制动压力0.57,0.67,0.72MPa)设计摩擦磨损试验,研究了不同复合材料的摩擦磨损行为。结果表明:所得SiC_(p)/Al复合材料均组织致密,无裂纹和气孔缺陷,SiC颗粒均匀分布在铝合金基体中,无团聚现象;复合材料的抗拉强度、断后伸长率和硬度均满足制动盘行业标准要求,随SiC颗粒体积分数的增加,抗拉强度变化幅度较小,断后伸长率呈降低趋势,硬度呈升高趋势;当SiC颗粒体积分数为25%和30%时,复合材料的平均摩擦因数稳定在0.3~0.5,满足市域列车高速制动要求,磨损表面未发现明显的犁沟和分层,表面形成了完整的摩擦膜,但是SiC颗粒体积分数为30%的复合材料对偶闸片的磨损量较高,且在0.57MPa制动压力下的摩擦稳定系数较低,摩擦副的匹配性差;当SiC颗粒体积分数为20%时,最大平均摩擦因数大于0.55,磨损表面犁沟和分层现象明显,磨粒磨损严重,最大犁沟深度达到45μm,无法满足市域列车高速制动要求。

SiC_(p)/Al composites with SiC particle volume fractions of 20%,25%and 30%were prepared by stir casting combined with friction stir processing.The microstructure and mechanical properties of the composites were studied.The friction and wear tests were designed based on the actual operating conditions of trains in the city(braking pressure of 0.57,0.67,0.72 MPa),and the friction and wear behavior of different composites was studied.The results show that SiC_(p)/Al composites with different SiC particle volume fractions had dense structure with no cracks and porosity defects,and SiC particles were uniformly distributed in the aluminum alloy matrix without agglomeration.The tensile strength,percentage elongation after fracture and hardness of the composites met the requirements of the brake disc industry standard.With the increase of SiC particle volume fraction,the tensile strength change range was small,the percentage elongation after fracture decreased and the hardness increased.The average friction coefficient of composites with 25%and 30%volume fraction of SiC particles remained stable in the range of 0.3‒0.5,meeting the high-speed braking requirements of urban trains;no obvious grooves or delamination were found on the wear surface,and a complete friction film was formed on the surface.However,the brake disc pairing with composites with SiC particle volume fraction of 30%had high wear amount,and the friction stability coefficient was low at 0.57 MPa braking pressure,indicating poor matching of friction pair.The maximum average friction coefficient of composites with SiC particle volume fraction of 20%was greater than 0.55,and the wear surface showed obvious grooves and delamination with severe abrasive wear,and the maximum groove depth reached 45μm;the composites could not meet the high-speed braking requirements of urban trains.