Effects of matrix and reinforcement properties on low- and high-cycle fatigue behaviour of particulate-reinforced MMCs

Abstract

High and low-cycle fatigue tests were performed on AA 6061/10%Al2O3p, AA 6061/20%Al2O3p and AA 2618/20%Al2O3p metal matrix composites. All the materials were tested in a peak-aged condition (T6 temper). The fatigue properties were analysed in terms of reinforcement and particle/matrix interface properties; the effect of reinforcement volume fraction and size was also studied. OM, SEM and EDS analyses were performed on the composites. SEM analyses were also carried out on the fracture surfaces of fatigue-tested samples to assess crack nucleation and growth mechanisms. Differences between low and high-cycle fatigue and fracture behaviour were discussed for the tested composites. In the high-cycle fatigue regime, the materials showed better resistance than the corresponding un-reinforced alloys only at low stresses. The composite resistance to the low-cycle fatigue was less satisfactory. In this case, a coarser reinforcement reduced the fatigue life, due to greater tendency toward particle damage on loading.