HIGH-TEMPERATURE FLOW AND FAILURE PROCESSES IN AN AL-13WT-PERCENT SI EUTECTIC ALLOY

A maximum elongation of 250% was achieved in a Al-13 wt % Si eutectic alloy (similar to 18 mu m grain size) when deformation was carried out at 557 degrees C at a strain rate of 1 x 10(-2) s(-1). The shapes of the true stress-true strain curves obtained in this investigation are different from those reported by Chung and Cahoon [1]. It is felt that this is due to differences in the processing of the alloys used in th e two investigations. The higher elongation obtained at a strain-rate of 1 x 10(-2) s(-1) as compared to 4.6 x 10(-4)s(-1) is attributed to a higher strain rate sensitivity, lower rain and particle coarsening a nd a lower revel of cavitation at the former strain rate. It is believ ed that the mechanism of high temperature flow in this system is by gr ain boundary sliding accommodated by dislocation motion. The latter is rate controlled by the climb of dislocations over hard Si particles.