Initiation and Growth Behavior of Small Surface Fatigue Cracks on SiC Particle Reinforced Aluminum Composite

Reversed plane bending fatigue tests were conducted on SiC particle reinforced aluminum composite which was consolidated by Powder Metallurgy (P/M) process. The initiation and growth of small surface cracks were monitored by a plastic replica technique and investigated in detail. A fatigue crack initiated in matrix in the vicinity of SiC particle by cyclic slip deformation. It was found that the fatigue crack deflected along SiC particles and grew in a zig-zag manner microscopically, although the crack propagated straigth in the direction normal to the loading axis macroscopically. Micro subcracks frequently initiated in the front of main crack and coalesced. The fatigue crack growth rate was found faster in small crack than that in long crack.