HIGH-TEMPERATURE DEFORMATION OF 6061-AL

The creep behavior of powder metallurgy (PM) 6061 Al, which has been u sed as a metal matrix alloy in the development of discontinuous silico n carbide reinforced aluminum (SiC-Al) composites, has been studied ov er six orders of magnitude of strain rate. The experimental data show that the steady-state stage of the creep curve is of short duration; t hat the stress dependence of creep rate is high and variable; and that the temperature dependence of creep rate is much higher than that for self-diffusion in aluminum. The above creep characteristics are diffe rent from those documented for aluminum based solid-solution alloys bu t are similar to those reported for discontinuous SiC-Al composites an d dispersion-strengthened (DS) alloys. Analysis of the experimental da ta shows that while the high stress dependence of creep rate in 6061 A l, like that in DS alloys, can be explained in terms of a threshold st ress for creep, the strong temperature dependence of creep rate in the alloy is incompatible with the predictions of available threshold str ess models and theoretical treatments proposed for DS alloys.