Tensile Properties of AZX612 Magnesium Alloy Sheets Processed by Friction-Assisted Extrusion

摘要

Tensile properties at room and elevated temperatures of AZX612 alloy sheets processed by a kind of lateral extrusion method namely Friction-Assisted Extrusion (FAE) were investigated. The FAE was developed to control the texture, and carried out at temperatures ranging from 250 to 350℃ with an extrusion ratio of 4 from the as-rolled condition. The results showed that FAE changes the basal texture of the as-rolled sheet into that inclined by about 15° against the extrusion direction and raises the intensity of the texture. It was observed that the significant microstructure refinement from as-rolled condition of 10.8μm to 4.7μm after FAE due to dynamic recrystallization at the extrusion temperature of 250℃. The 0.2% proof stress of the FAEed sheets at room temperature became significantly smaller than that of the as-rolled sheet in the extrusion direction but became larger in the transverse direction, resulting in the larger anisotropy. This can be understood by the activity of basal slip. The anisotropy of the tensile properties disappeared at a temperature of 300℃ and an initial strain rate of 3.3×10~(-4)s~(-1). In addition, the elongation was improved from 72% of the as-rolled sheet to 152% at maximum of the FAEed sheets in the extrusion direction. This improvement was attributable to superplastic flow based on grain boundary sliding.