Influence of temperature on segregation in 2009 Al-SiC w composite and its implication on high strain rate superplasticity

Abstract

A number of aluminum matrix composites exhibit high strain rate superplasticity. Two experimental features stand out. First, the optimum strain rates for superplasticity are > 1 {times} 10{sup {minus}1} s{sup {minus}1}, significantly higher than conventional superplastic strain rates of 10{sup {minus}4}--10{sup {minus}3} s{sup {minus}1}. Second, a correlation exists between the temperature at which the maximum superplastic elongation is observed and the incipient melting temperature. This has led to some debate on the mechanism of high strain rate superplasticity. To investigate the role of ceramic reinforcement on the segregation at high temperatures, the authors have conducted the following experiments: (a) the effect of prior thermomechanical processing on high strain rate superplasticity, and (b) the influence of temperature on segregation by carrying out analysis during in-situ heating in a transmission electron microscope (TEM). This work was carried out on a 2009 Al-SiC{sub w} composite.