Twinning and slip behaviors and microstructural evolutions of extruded Mg-1Gd alloy with rare-earth texture during tensile deformation

Abstract

An extruded Mg-1Gd alloy with a non-basal texture, whose basal poles are tilted 60.9° from the extrusion direction (ED), exhibits a high room-temperature tensile elongation of 37.2%. This study investigates the active deformation mechanisms and microstructural evolutions of this highly ductile extruded alloy during tensile deformation through in situ electron backscatter diffraction analysis. When tensile strain is applied along the ED, a small amount of {10-12} twins is formed at the early stage of deformation, and the twins gradually grow with increasing applied strain. However, {10-11} twins and {10-11}-{10-12} twins, which are generally observed in extruded Mg alloys with a typical basal fiber texture, are not formed during deformation. The tilted initial texture is favorable for basal slip, and therefore, basal slip is vigorously activated during tension. As a consequence, the average angle between the c-axis of the grains and the ED increases from 60.9° to 66.3° as the applied tensile strain increases from 0% to 30%. Prismatic slip is also activated during tension, which is confirmed by the gradual increase in the rotation angle of the prismatic poles around the <0001> axis during deformation. The activation of prismatic slip causes a significant reduction in the texture intensity of the alloy during deformation. The high ductility of the Mg-1Gd alloy is attributed mainly to the activation of {10-12} twinning, which is beneficial to elongation, instead of the activation of {10-11} twinning, which is detrimental to elongation, and the promoted activation of basal and non-basal slips. Furthermore, microstructural characteristics such as the fully recrystallized structure, large average grain size, and absence of second-phase particles also contribute to the high ductility of the alloy.