Effect of particulate silicon carbide on cyclic strain resistance and fracture behavior of X2080 aluminum alloy metal matrix composites

Abstract

A study has been made to understand the low-cycle fatigue properties and fracture behavior of aluminum alloy X2080 discontinuously-reinforced with varying amounts of silicon carbide particulates. The X2080/SiC p composite specimens were cyclically deformed over a range of cyclic-strain amplitudes, using tension-compression loading under total strain amplitude control, giving fatigue failure lives of less than 10 4 cycles. The X2080/SiC p composites exhibited hardening at all cyclic plastic strain amplitudes and for the different volume fractions of the discontinuous reinforcement in the ductile metal matrix. The degree of cyclic hardening was observed to be greater at the higher cyclic strain amplitudes than at corresponding lower strain amplitudes. Micromechanisms controlling the hardening response during cyclic straining are highlighted and rationale for the observed hardening behavior is discussed. The plastic strain-fatigue life response was found to degrade with an increase in carbide particle content in the aluminum alloy matrix. The cyclic fracture behavior of the composite is discussed in light of composite microstructural effects, cyclic plastic strain amplitude and concomitant response stress.