EFFECTS OF SICP SIZE AND VOLUME FRACTION ON THE HIGH-CYCLE FATIGUE BEHAVIOR OF AZ91D MAGNESIUM ALLOY COMPOSITES

High cycle fatigue tests (i.e., stress-controlled, axial) were conduct ed on monolithic AZ91D and AZ91D magnesium alloy composites processed via squeeze casting and extrusion to contain either 15 mu m or 52 mu m size SiC particles, at both the 20% and 25% volume fraction reinforce ment level. The effects of changes in SIC particle size and volume fra ction on the high cycle fatigue behavior have been determined. In addi tion, the number of cracked particles on the fatigue fracture surfaces , as well as the level of damage beneath the fatigue fracture surfaces were quantified in order to determine the effects of particle size on the evolution of damage during fatigue and during overload failure. C ommercial purity Mg specimens containing a large grain size were also tested in fatigue for comparison with the alloy and composite data.