Some observations on the shear fracture mode in AlMg6.5 alloy sheet

Abstract

AlMg6.5 alloy sheet samples with different width to thickness ratio (w/t=2.5-8.3) were tested in uniaxial tension test. SEM observations revealed transgranular ductile dimple type of failure occured by shear process. It was found that the orientation of fracture surface depends on the w/t ratio (due to the transition from plane stress (w/t=6.3-8.3) to plane strain (w/t=2.5-5) condition) and also on the grain size (through the grain size effect on the intensity of PLC bands appearance). At high w/t ratio, w/t=6.3-8.3, fracture occurs at ~60-70° to the tensile axis, parallel to the PLC bands, which are very intensive in that case. For low w/t ratio, w/t=2.5-5, PLC bands are less evident, and fracture occurs at ~55° through the specimen thickness and at ~90° to the tensile axis.