Low Temperature Superplasticity of High-Strength Ultrafine-Grained Al 7050 alloy

摘要

Ultrafine-grained (UFG) Al 7050 alloy of the 7xxx series demonstrates very high strength at room temperature with UTS=845 MPa and hardness Hv=255, which considerably exceeds the value after conventional heat treatment T73, i.e. Hv=165. It is also revealed that with increasing temperature the alloy exhibits rather high ductility with elongation to failure δ=170% at 120 °C and strain rate of 5×10~(-4) s~(-1) and typical superplastic behavior with 5=480% and δ=690% at temperatures 170 °C and 200 °C correspondingly. Such values of superplasticity (S) temperature are considerably lower than that typical of this alloy with micron-sized grains (T_(SP)=450-500 °C). Such reduction in superplasticity temperature made it possible to preserve ultrafine grains in the alloy structure and provide its high-strength state after SP straining.