Effect of {10-11} contraction and {10-11}-{10-12} double twins on the subsequent deformation behavior of two Mg alloys

Mg alloy tubes are frequently bent prior to hydroforming. As a result, such metals are subjected to reversals of strain path. It is therefore useful to know the effects of changing strain path as well as of twinning on the stress-strain response after the change. In this study, experiments were designed and conducted to introduce contraction and double twins during tensile prestraining. These samples were subsequently compressed at a strain rate of 0.1s^-1 and at ambient temperature as well as at 200°C The results indicate that the compressive (second) deformation is initially slip-dominated, which is then followed by extension twin-dominated deformation. An annealing treatment (holding at 300°C for one hour) was performed on some of the prestrained tensile samples. By annealing heavily extended (ε=0.15) material containing contraction and double twins, the grain size was very effectively refined and the texture was modified as well.