Effect of dynamic strain aging on the deformation and twinning behavior of a Mg-2Zn-2Nd alloy

Constant strain rate compression tests were carried on samples of Mg-2Zn-2Nd that had been either: (i) slowly cooled or (ii) solutionized and quenched. Peaks in the flow stress/temperature curves were observed, indicating that dynamic strain aging (DSA) was taking place at certain temperatures and strain rates. This led to the presence of both negative as well as high positive strain rate sensitivity (SRS) regions. The quenched material displayed a wider range of negative SRS owing to its higher Nd solute content. Compression samples of the slowly cooled material deformed under positive SRS conditions contained large extension and contraction twins. By contrast, samples deformed under negative SRS conditions contained fine extension twins located entirely within the shear bands. The twin variants that formed in the negative SRS sample were characterized by high Schmid factors and required accommodation by a combination of basal, prismatic and pyramidal glide.