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 microstructure 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 fractions of the carbide particulate reinforcement phase, in the aluminum alloy matrix, are considered. Quasi-static fracture of the composite comprised cracking of the individual and clusters of particulates present in the microstructure. Particulate cracking increased with reinforcement content in the aluminum alloy matrix. Final fracture occurred as a direct result of crack propagation through the matrix between particulate clusters. The composite specimens were cyclically deformed under fully-reversed, total strain-amplitude-controlled cyclic straining, giving lives of less than 10(4) cycles to failure. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The cyclic fracture behavior of the composite is discussed in light of concurrent and mutually interactive influences of composite microstructural effects, matrix deformation characteristics, cyclic plastic strain amplitude and resultant response stress. (C) 1998 Elsevier Science Ltd.