Hot deformation behavior in Mg-Al alloy, AZ91D grain refined by isothermal-rolling

The isothermal-rolling mill has been developed for non-working materials, for example, like Mg-Al alloy. The recrystallization behavior of Mg-Al alloy, AZ91D has been investigated. The starting and finishing temperatures of recrystallization are 523K and 648K, respectively. AZ91D sheets tempered to fine grain size by recrystallization have been prepared and tensed at high temperatures. Both the total elongation and strain-rate sensitivity m have been obtained and discussed. The values of total elongation have exceeded over 100% at testing temperature over 623K with strain-rate below 1.0 x 10(-2) s(-1) and 170% of maximum total elongation has been obtained. The ill values have indicated over 0.5 in range of 1.0 x 10(-4) s(-1) to 2.5. x 10(-4) s(-1) except testing temperature of 573K. The activation energy required for high temperature deformation has been calculated to be about 124kJ.mol(-1), which is almost same of the activation energy for self-diffusion coefficient in Mg. Therefore, the deformation of AZ91D has been accommodated by volume diffusion.