Influence of grain size on twinning behavior of WE43 magnesium alloy during room-temperature compression deformation

Abstract

In the present study, room-temperature compression experiments and characterization experiments via optical microstructure (OM), X-ray diffractometer (XRD) and electron backscattered diffraction (EBSD) techniques were conducted on WE43 magnesium (Mg) alloy samples to investigate the grain size effect on twinning behavior. Three couples of solution treatments (823 K for 0.5 h, 798 K for 8 h, 823 K for 16 h, followed by water-quenching at ⁓333 K) were adopted and these solutionized samples are with different grain sizes of 48.5, 72.0 and 120.2 μm, respectively. Results show that {10-12} extension twin (ET) and {11-21} ET serve as major twinning modes during plastic deformation. For all 7.7%-deformed samples, although the volume fractions of {10-12} ETs and {11-21} ETs increase with the increasing grain size. {10-12} ETs are in growth stage, while {11-21} ETs are mainly in nucleation stage and they still maintain narrow and parallel to each other. Besides, {10-12} ETs mainly contribute to the rotation of c-axes of grains towards compression direction, while {11-21} ETs mainly contribute to the formation of a nearly ring-shaped texture component in (0002) pole figure. Twin variants analysis with the assistance of Schmid factor (SF) demonstrates that the activation of twin variants mainly obeys Schmid law. When only {10-12} ETs occur in individual grains, the maximum number of twin variants shows some positive relationship with the increasing grain size. By comparison, when both {10-12} ETs and {11-21} ETs occur in individual grains, the maximum numbers of twin variants are rarely influenced by the increasing grain size.