Quasi-in-situ EBSD analysis of twinning and detwinning in ZCW610 alloy

Abstract

The twinning and detwinning behavior of ZCW610 alloy during two-step intermittent dynamic compression along extrusion direction (ED) and extrusion radial direction (ERD) was studied by quasi-in-situ electron backscatter diffraction (EBSD). Experiments show that 160 twins with a volume fraction of 16.96% form at 4% strain along ED for the first step. When compressed to 4% strain along ERD next, 60 new twins are generated, while 41 twins undergo detwinning with the final volume fraction reaching 19.07%. When the strain increases, the number of newly generated twins is always more than that of detwinning, and the Schmid factor (SF) of most activated twinning and detwinning variants rank first or second, indicating that twinning is easier to accommodate deformation than detwinning. Two low SF tensile twin variants are found: those formed at grain boundaries and twin pairs with intersecting boundaries. Twin variant selection depends on both Schmid's law and strain compatibility factor (m'), where low SF variants nucleate via stress concentration in adjacent grains due to high m'. Detwinning across low angle grain boundaries releases tip stress, proving shear stress from internal stress can activate low SF twins. Low SF twins generated by compression along ED can reorient parent grains and activate slip. ED-compressed low SF twins reorient parent grains and activate slip, while ERD stress reverses their resolved shear stress, driving detwinning migration. This study elucidates the key influencing factors and mechanisms of twinning and detwinning under biaxial dynamic compression, providing theoretical support for material deformation research.