Research on clarication of fatigue mechanism in metal matrix composites and evaluation method for its mechanical characteristics

本研究对粉末冶金制备的碳化硅晶须增强6061-T6、2024-T4和7057-6T铝合金进行了旋转弯曲和推拉疲劳试验，研究了平面试件和缺口试件的室温疲劳机制。利用塑性复制法对三种材料的疲劳机理进行了连续的表面观察。结果表明：(1)所有MMC的疲劳强度都有所提高，与钢相当。(2)在小裂纹的疲劳扩展寿命中消耗了100um的疲劳寿命。(3)所有MMC都具有缺口敏感性，且带钝缺口的疲劳极限具有很大的统计系数。(4)从(3)和f(4)中可以看出，所有MMC的疲劳寿命都有很大的离散性。(5)统计疲劳寿命的一种简单预测方法是重要的。(6)对于每种力学性能，都存在一个最佳的碳化硅晶须体积分数。并且它依赖于矩阵的特性。

In this research, rotating-bending and push-pull fatigue tests of the SiC whisker reinforced 6061-T6,2024-T4 and 7057-6T aluminum alloy made by powder metallurgy were carried out to investigate the fatigue mechanism of plain and notched specimens at room temperature. The fatigue mechanisms in three materials were clarified through successive surface observations using the plastic replica method. Obtained results are as follows.(1) Fatigue strength of all MMC increase and are about as high as the steel.(2) The fatigue life is consumed in the fatigue propagation life of small crack by 100mum.(3) All MMC has a notch sensitivity, and the fatigue limit with a blunt notch has a large statistical factor.(4) It is indicated from (3) andf (4) that the fatigue life of all MMC has a large scatter.(5) A simple method for predictiction of statistical fatigue life is important.(6) There is an optimum volume fraction of SiC whisker for each mechanical property, and it is dependent on the characteristics of matrix.