Superplasticity of Ultra-Fine Grained 7075 Alloy Processed by High-Pressure Torsion

Abstract:

An Al 7075 alloy (5.63mass%Zn-2.56mass%Mg-1.68mass%Cu-0.21mass%Fe-0.19mass%Cr-0.14mass%Si-0.02mass%Ti with balance of Al) was processed by high-pressure torsion (HPT) under an applied pressure of 6 GPa for 1, 3 and 5 revolutions with a rotation speed of 1 rpm at room temperature. Vickers microhardness saturated to a level of 220 Hv after the HPT processing and the grain size was refined to 120 nm at the state of the hardness saturation. Tensile tests were conducted with initial strain rates from 2.0 × 10^-4 to 2.0 × 10^-2 s^-1 at temperatures as 200 °C and 250 °C (equivalent to 0.52T_m and 0.57T_m, respectively, where T_m is the melting point of the alloy). The HPT-processed samples for 3 revolutions exhibited superplastic elongations of 640% and 510% at 250 °C with initial strain rates of 2.0 × 10^-3 s^-1 and 2.0 × 10^-2 s^-1, respectively.

• Periodical: Materials Science Forum (Volumes 794-796)
• Pages: 807-810
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.794-796.807
• Online since: June 2014
• Authors: Seungwon Lee*, Zen Ji Horita
• Keywords: AA7075, Grain Refinement, High-Pressure Torsion, Superplasticity

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