Strong strain path dependence of strain localizations and fracture in magnesium AZ31 sheet

摘要

This study compares the deformation and fracture behavior of a basal-textured Mg AZ31 alloy sheet under uniaxial tension and biaxial stretching by using an in-plane biaxial test setup capable of observing and measuring the deformation at both meso(millimeter)and microstructure scales.Strain distributions at the mesoscale and accompanying fracture surfaces indicate a significant dependence on strain path.At the microscale,limited slip activity in biaxial case promotes contraction twins,where severe strain localizations(εmax/εmean≈220)to the twins and their boundaries cause mainly transgranular fracture.This leads to a brittle,and a more pronounced shear-type fracture under biaxial stretching.In uniaxial case,considerable tensile twinning activity reorients the initial texture for slip activity.Strain localizations(εmax/εmean≈2)to the grain interiors and boundaries initiate mainly intergranular fracture.Samples fail by displaying both brittle and ductile fracture structures,with smaller shear lips compared to the biaxial case.