An examination of the effect of processing procedure on the creep of metal matrix composites

Creep data were examined for two metal matrix composites having an Al-6061 alloy as the matrix and fabricated using either powder metallurgy (PM) or ingot metallurgy (IM) procedures. Although the results from these two composites suggest the possibility of different rate-controlling creep mechanisms, it is shown by analysis that the behavior of the two composites is mutually consistent and in agreement with the expectations from earlier creep data using dilute Al–Mg solid solution alloys. It is demonstrated that the processing procedure has an important influence on the values of the measured threshold stresses. For these two composites, the threshold stresses are consistently higher in the PM composite at any temperature, by a factor of ≈3, and this is attributed to the additional obstacles to dislocation movement, in the form of fine oxide particles, which are introduced during the atomization process.