High Strain Rate Superplasticity of in situ Al3Zr/6063Al Composites

In situ 5wt%Al3Zr/6063Al composites were fabricate by a direct melt reaction method (DMR) and then processed by deformation pretreatment. Process of the pretreatment was forging of 70% deformation at 450 °C and friction stir processing (FSP). The high strain rate superplasticity of the composites was studied by modern analytic determination methods. The results show that the average grain size of the composites is less than 10 μm after forging and FSP. The composites exhibit superplasticity at the temperature from 350 to 500 °C and initial strain rate from 1.0×10−3 s−1 to 1.0×10−1 s−1. The elongation reaches 330% and the sensitive index (m value) is 0.45 at the initial strain rate of 1.0×10−2 s−1 and the temperature of 500 °C. The dominant mechanisms of superplastic deformation are grain boundary sliding and dislocation slip which is synergized with moderate grain growth and dynamic continuous recrystallization