A COMPARISON OF THE CREEP-PROPERTIES OF AN AL-6092 COMPOSITE AND THE UNREINFORCED MATRIX ALLOY

Creep tests were conducted on an Al-6092 alloy reinforced with 25 vol pet SIC particulates and on an unreinforced Al-6092 matrix alloy. Both materials exhibit creep behavior indicating the presence of a thresho ld stress and both have a true stress exponent of 3, but with measured activation energies for creep of similar to 135 and similar to 230 kJ mol(-1) in the unreinforced and reinforced materials, respectively. B y incorporating a temperature-dependent load transfer into the analysi s, it is shown that the activation energy for the composite is reduced to similar to 130 kJ mol(-1). Both materials therefore exhibit creep behavior consistent with viscous glide and the dragging of Mg solute a tmospheres, and in addition the results for the composite are consiste nt with the proposal that the creep of metal matrix composites divides into two classes depending upon the rate-controlling process in the m atrix alloys.