Superplasticity of a SiCp/Al-10wt%Ti composite at high strain rates

Abstract

A SiC particle reinforced Al-10wt%Ti composite was manufactured by a powder metallurgy process using SiC particles of about 8 mu m and gas atomized powders of Al-10wi%Ti, and the microstructure consisted of fine equiaxed grains with uniform dispersion of SiC and Al3Ti particles was produced. Superplastic behavior has been investigated at 600 similar to 650 degrees C and strain rates of 10(-3) similar to 10(-1) sec(-1) in tension test. The composite exhibited a strain-rate sensitivity(m) higher than 0.33 and total elongation of 250 similar to 400% was observed at strain-rate of 10(-1) sec(-1). Threshold stress(sigma(o)) was determined by the linear interpolation method and used to understand the effective stress(sigma - sigma(o)) vs. strain-rate((epsilon) over dot) data. Based on the fact that the stress exponent of 2 correlate the experimental data well, the mechanism for the high strain-rate superplasticity of the SiCp/Al-10wt%Ti composite was analyzed to be the grain boundary sliding. The incorporated threshold stress showed strong temperature dependence as in the similarly processed RSP Al-10wt%Ti alloy. This analysis revealed that the addition of 5vol% SiC particles did not affect the superplastic property of the fine grained Al-10wt%Ti alloy.