Examining the mechanical properties and superplastic behaviour in an Al-Mg-Sc alloy after processing by HPT

P.H.R. Pereira1, Y. Huang1, T.G. Langdon1,2*
1Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, U.K.
2Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453, U.S.A.
Abstract
Experiments were conducted using the solution treated Al-3 % Mg-0.2 % Sc alloy in order to examine the mechanical properties and superplastic behaviour after processing by high-pressure torsion. Hardness values of ~200 Hv were detected in the edge of the samples after 10 turns of HPT, although the microhardness distribution was inhomogeneous along the diameter of the discs. Excellent superplastic properties were achieved in this Al alloy after HPT processing and further tensile testing at temperatures over the range from 523 to 673 K, demonstrating good agreement with the theoretical model for grain boundary sliding. High strain rate superplasticity was consistently observed at temperatures from 573 to 623 K, with elongations to failure up to ~800 % at 573 K and at a strain rate of 1.4×10-2 s-1. Further analysis of the experimental data revealed that the stress exponent at the testing conditions displaying elongations >400 % was ~2 thereby demonstrating good agreement with the theoretical model for grain boundary sliding. The calculated activation energies lie in the range from ~98 to ~118 kJ mol-1 and are similar to the value obtained for the same alloy after ECAP which is within the range for grain boundary diffusion in pure Al and interdiffusion in Al-Mg alloys.
Accepted: 19 March 2015
Views: 144   Downloads: 35
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