Hot Tensile Deformation Behavior of Twin Roll Casted 7075 Aluminum Alloy

摘要

High temperature deformation behavior of the 7075 aluminum alloy sheets fabricated by twin roll casting and rolling was investigated by hot tensile tests at different temperatures from 350 to 500 degrees C and various initial strain rates from 1x10(-3) to 1x10(-2) s(-1). The results show that flow stress increased with increasing initial strain rate and decreasing deformation temperature. A large elongation of 200% was obtained at relatively high strain rate of 5x10(-3) s(-1) at 450 degrees C. It is closely related with the grain boundary sliding at elevated temperature attributed to the recrystallized fine grains and the large volume fraction of high-angle grain boundaries. The fracture transformation mechanism changes from ductile transgranular fracture to ductile intergranular fracture due to the recrystallized fine grains at high temperature. High density and uniform cavities observed in large elongation samples at high temperature reveals the contribution of grain boundary sliding. Necking-controlled failure mode was characterized by rare cavities with low elongation.