2005 Volume 91 Issue 8 Pages 647-654
Thin magnesium alloy of AZ91D sheets worked by isothermal-rolling and then annealed around the temperature between 0% and 100% recrystallization have been prepared, and tensed at right angles to rolling direction at elevated temperatures and at several strain-rates. Both the total elongation and strain-rate sensitivity m have been obtained and discussed.
The m values was found to be 0.5 in range of 1.0 × 10-4s-1 to 1.0 × 10-3s-1. The activation energy required for superplastic deformation was calculated to be about 87 kJ ·mol-1, which was almost same of the activation energy for self-diffusional grain boundary coefficient in Mg.
Although the high strain-rate sensitivity and the activation energy corresponding to self-diffusional grain boundary were obtained, contrary to expectations, the values of total elongation didn't exceed over 100% at all testing temperatures and at all strain-rates.
Tensed at right angles to rolling direction, gap and offset presupposed during tensile testing were not accommodated by recrystallized anisotropic fine particles. Therefore, a large number of cavities caused, and consequently the total elongations decreased.
