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 threshold 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. By incorporating a temperature-dependent load transfer into the analysis, 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 atmospheres, and in addition the results for the composite are consistent with the proposal that the creep of metal matrix composites divides into two classes depending upon the rate-controlling process in the matrix alloys.