CYCLIC PLASTIC STRAIN RESPONSE AND FRACTURE-BEHAVIOR OF 2080-ALUMINUM-ALLOY METAL-MATRIX COMPOSITE

A study has been made to understand the role of composite microstructu re on failure through mechanisms governing the quasi-static and cyclic fracture behavior of aluminum alloy X2080 discontinuously-reinforced with silicon carbide (SiC) particulates. Two different volume fraction s of the carbide particulate reinforcement phase, in the aluminum allo y matrix, are considered. Quasi-static fracture of the composite compr ised cracking of the individual and clusters of particulates present i n the microstructure. Particulate cracking increased with reinforcemen t content in the aluminum alloy matrix. Final fracture occurred as a d irect result of crack propagation through the matrix between particula te clusters. The composite specimens were cyclically deformed under fu lly-reversed, total strain-amplitude-controlled cyclic straining, givi ng lives of less than 10(4) cycles to failure. The plastic strain-fati gue life response was found to degrade with an increase in carbide par ticulate content in the metal matrix. The cyclic fracture behavior of the composite is discussed in light of concurrent and mutually interac tive influences of composite microstructural effects, matrix deformati on characteristics, cyclic plastic strain amplitude and resultant resp onse stress. (C) 1998 Elsevier Science Ltd.