THE LOW-CYCLE FATIGUE BEHAVIOR OF AN ALUMINUM-ALLOY CERAMIC-PARTICLE COMPOSITE

A study has been made to understand the low-cycle fatigue and cyclic fracture behaviour of the aluminium alloy 2124, which is discontinuously reinforced with varying volume fractions of silicon carbide particulate. The Al/SiC(p) composites were cyclically deformed over a range of strain amplitudes giving lives of less than 10(4) cycles to failure. The specimens were cycled using tension-compression loading and under total strain control. The 2124 + SiC(p) composites, in the as-extruded condition, displayed cyclic hardening at all strain amplitudes and for the different volume fractions of reinforcement in the ductile metalmatrix. The material rapidly softened prior to failure. The cyclic hardening behaviour increased with an increase in carbide particle content. The plastic-strain-fatigue life response of the Al/SiC(p) composite was found to degrade with an increase in carbide particle content in the metalmatrix. The observed hardening, culminating in rapid softening, is attributed to the synergistic and competing influences of dislocation multiplication, mutual interaction among dislocations, and an interaction of mobile dislocations with the reinforcing carbide particle. The cyclic fracture behaviour of the composite is discussed in the light of intrinsic composite microstructural effects, plastic-strain amplitude and the resultant response stress.