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采用紧凑拉伸试样进行恒载和降K控制的拉-拉疲劳实验,研究了喷射沉积SiC_p/Al-7Si复合材料及其基体的疲劳裂纹扩展行为.通过金相显微镜和扫描电镜观察了复合材料及其基体的组织和疲劳裂纹扩展形貌,研究了SiC颗粒对复合材料疲劳裂纹扩展机制的影响.结果表明:复合材料在任何相同的ΔK水平下其抗疲劳裂纹扩展能力优于基体材料,并表现出较高的疲劳门槛值.其原因是复合材料中裂纹裂尖遇到增强颗粒时,裂纹发生偏转,特别是SiC颗粒自身微裂纹萌生有效降低了裂纹尖端的应力强度因子,复合材料的裂纹闭合效应也随之增大.去除裂纹闭合效应的影响,当有效应力因子△K_(eff)作为裂纹扩展的驱动力时,复合材料的裂纹扩展速率却高于基体.
The fatigue crack growth behavior of spray-deposited SiCp / Al-7Si composites and its matrix was investigated by pull-pull fatigue tests with compact tensile test specimens under constant load and drop K control. The mechanical properties of composites were investigated by metallographic and scanning electron microscopy The effect of SiC particles on the fatigue crack propagation mechanism of the composites was investigated. The results show that the fatigue crack growth resistance of the composites is better than that of the matrix at any same ΔK level, And showed a higher fatigue threshold.The reason is that the crack tip is deflected when the crack tip of the composite encounters the reinforced particles, especially the microcracking initiation of the SiC particles effectively reduces the stress intensity factor of the crack tip, and the composite material The effect of crack closure is also removed.When the effective stress factor △ K eff is used as the driving force of crack propagation, the crack propagation rate of the composite is higher than that of the matrix.