Superplasticity of a SiC_p/AI-10wtTi Composite at High Strain Rates

摘要

A SiC particle reinforced Al-10wt%Ti composite was manufactured by a powder metallurgy process using SiC particles of about 8μm and gas atomized powders of Al-10wt%Ti, and the microstructure consisted of fine equiaxed grains with uniform dispersion of SiC and Al_3Ti particles was produced. Superplastic behavior has been investigated at 600 ～ 650℃ and strain rates of 10~(-3) ～ 10~(-1) sec~(-1) in tension test. The composite exhibited a strain-rate sensitivity(m) higher than 0.33 and total elongation of 250 ～ 400% was observed at strain-rate of 10~(-1) sec~(-1). Threshold stress(σ_o) was determined by the linear interpolation method and used to understand the effective stress(σ - σ_o) vs.rnstrain-rate(ε) 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 SiC_p/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.