Effects of volume fraction of alumina short fibers on high cycle fatigue properties of Al and Mg alloy composites

Rotating bending fatigue tests in high cycle fatigue regime were carried out on alumina short fiber reinforced aluminum alloy composites (Al-MMCs) and magnesium alloy composites (Mg-MMCs). Materials of an aluminum alloy A6061 and a magnesium alloy AZ91D, and three volume fractions of 10%, 18%, and 25% of alumina short fibers were prepared to investigate effects of fiber volume fraction on fatigue properties such as a fatigue strength, surface crack initiation, and propagation behaviors. As results, it was found that the fatigue strength increased with an increase of volume fraction of alumina fibers in both MMCs, and the fatigue strength in Al-MMCs at elevated temperature was improved by the alumina short fibers reinforcement. The crack initiation sites were larger size alumina fibers, cluster of short fibers and large size alumina particles in both MMCs.