Twinning behavior of hot extruded AZ31 hexagonal prisms during uniaxial compression

Abstract

Hot-extruded magnesium alloy AZ31 bar was cut into hexagonal prisms and then compressed at room temperature with the loading direction parallel to the extrusion direction (ED) or perpendicular to ED. The effective stress and strain evolution at center and corner region of the hexagonal prisms was simulated by using DEFORM 3D, while microstructure evolution was characterized by electron backscatter diffraction (EBSD). Relationship between twinning behavior and stress–strain evolution during compression at room temperature was studied. The results indicated that the compressive stress and strain levels at central region of hexagonal prisms were lower than those at the corner parts. EBSD examination revealed that {10-12} twins activate during the compression and the volume fraction of twins at corner parts were less than that at the central parts, which was attributed to twin thickening and coalescence behaviors. Meanwhile, the EBSD map indicated that the arise of {10-11} contraction twins and {10-11}-{10-12} double twins in compressed samples, especially in the corner region with loading axis perpendicular to ED, which were considered to be related to the high stress level at corner region. The dislocation slips led to low-angle boundaries in LA⊥ED and LA//ED. Keywords: Magnesium alloy, Simulation, Microstructure, Twinning, Coalescence