On the uniform elongation of cast Al–7%Si–0.6%Mg (A357) alloys

Continuously cast A357 alloy specimens that are essentially free from structural defects, such as oxide bifilms and porosity, were artificially aged at three different temperatures for various durations. The stress–strain curves of 90 specimens were analyzed. It was determined that in A357: (i) nonuniform elongation can be up to 38% of total elongation, (ii) nonuniform elongation can be as high as 5%, (iii) for the same yield strength, uniform elongation is a lower fraction of the total elongation in the overaged specimens than in the underaged, (iv) the strain-hardening exponent, n, of the Ludwik–Hollomon equation changes linearly with yield strength in underaged and overaged conditions, (v) n provides a poor estimate of the uniform elongation, and (vi) the Voce equation estimates the uniform elongation accurately.