Creep and substructure in 5 vol.% SiC–2124 Al composite

Abstract

The effect of stress and temperature on the creep behavior of powder metallurgy (PM) 5 vol.% silicon carbide particulate reinforced 2124 aluminum (SiC p–2124 Al composite) was studied over seven orders of magnitude of strain rates. Also, the data of the composite were compared with those of the unreinforced matrix alloy, PM 2124 Al, whose creep behavior was earlier investigated under similar experimental conditions. The results show that the origin of the anomalous stress dependence of the creep rate in the composite and the unreinforced matrix alloy is the presence of a threshold stress, τ o, which depends strongly on temperature. A substructural examination of crept samples suggests that the most probable source of τ o in PM 5 vol.% SiC p–2124 Al, like that in PM 2124, is related to the interaction between moving dislocations and dispersion particles which form as a result of processing both materials by powder metallurgy. Additionally, an analysis of the data of PM 5 vol.% SiC p–2124 Al reveals that the true creep behavior of the composite represents a modified form of the creep behavior of Al-based solid solution alloys in which deformation is driven not by the applied stress but rather by an effective stress, τ e ( τ e= τ− τ o). The true creep behavior of the composite is identical with that reported for the unreinforced matrix alloy, a finding which, when combined with substructural data, indicates that the deformation of the matrix controls the creep behavior of the composite.