Effect of stressed pre-exposure on the creep strengthening of a 2009 Al-SiC w composite

Abstract

Clearly the present approach of analyzing the steady state or minimum creep data on the basis on a threshold stress is not likely to produce an unambiguous interpretation of the steady state creep mechanism in aluminum alloy matrix composites. In the authors` opinion it is important to (a) establish the existence of a true steady state creep regime in tension over a large enough strain rate range (e.g. a typical creep rate range for experimental verification would be 10{sup {minus}9}--10{sup {minus}5} s{sup {minus}1}), (b) establish a criterion for the lack of a true steady state creep regime (in at least some composites), and (c) look for some other creep parameter to understand the differences in the creep behavior of composites and unreinforced matrices. In this paper the authors report the creep behavior of a 2009Al-SiC{sub w} composite (w denotes whisker). They note that no steady state creep regime was observed at higher creep rates. Specimens pre-exposed at a prior stress (and only in a critical range) show an unusual creep strengthening. This observation hints at the role of matrix composition on overall creep behavior of composites. The primary creep strain and anelastic strain values are reported to highlight the rolemore » of SiC{sub w} reinforcement on the overall dislocation activities during creep.« less