High-strain-rate superplastic flow in 6061 Al composite enhanced by liquid phase

High-strain-rate superplastic behavior of powder-metallurgy processed 0%, 10%, 20%, and 30% SiC particulate reinforced 6061 Al composites was studied over a range of temperatures from 430 to 610 degreesC. The strength of the 6061 Al composites was lower than that of the 6061 Al matrix alloy in the temperature range where grain boundary sliding is believed to control the plastic flow. The difference in their strength was also observed to be temperature dependent, increasing with increase in temperature. Abnormally high activation energy for superplastic flow was another important feature of the 6061 Al composites. These behaviors in particle weakening and activation energy have strong resemblance to those noted in the high-strain-rate superplastic 2124 Al composites studied previously. The observed particle weakening was attributed to liquid-enhanced superplastic flow and discussed by adopting the concept of effective diffusivity considering mass flow through liquid phase formed at the solute-segregated region near SiC/Al inter-faces.