EXPERIMENTAL INVESTIGATION OF SUPERPLASTIC BEHAVIOR IN MAGNESIUM ALLOYS

Constant strain rate tensile tests have been conducted for fine graine d Mg-Al-Zn (AZ91) and Mg-Zn-Zr (ZK60 and ZK61) alloys processed by pow der metallurgy (PM) and ingot metallurgy (IM) routes. The experimental results revealed that the strain rate was inversely proportional to t he cube of the grain size and that the activation energy for superplas tic flow was higher than that for grain boundary diffusion. The PM Mg alloys showed superplastic behaviour at higher strain rates than the I M Mg alloys. This is because of small grain sizes of the PM Mg alloys. The origin of the high strain rate superplasticity for the PM Mg allo ys is unlikely to be associated with the presence of a liquid phase. ( C) 1997 The Institute of Materials.