Orientation-related specimen thickness effects on mechanical properties of hot extruded AZ31B magnesium alloy

Microforming is a well-suited technology to manufacture very small metallic parts, in particular for mass production. Microforming is a plastic deformation forming technology. It is frequently found the material properties of wrought-metal products with stock size are not the same in all directions. The aspect of orientation dependency of the mechanical properties has been sufficiently investigated and reported in literatures. However, there are few literatures on the influence of orientation on the specimen size effect of material properties. The aim of this work is to study the specimen size effects of hot extruded magnesium alloys and their correlation with specimen orientation (or load direction). Tensile properties of a hot extruded AZ31B magnesium alloy were investigated using different specimen thicknesses in the range from 0.25 mm to 2 mm and three orientations at room temperature. Influences of the orientations on the size effects of the mechanical properties were also studied. Major results of the present work included: firstly, obvious size effect on mechanical properties of the alloy could be observed, and secondly, the size effects on the tensile strength depended on the orientations. The tensile yield strength and the tensile strength of the alloy along the extrusion direction increased with the specimen thickness, while these along the transverse direction and the 45o direction decreased with the thickness. The elongation percentage of the three orientations decreased with the thickness. The orientation affected the failure mode and the value of the fracture elongation. However, the orientation did not influence the size effects of failure mode and fracture elongation.