Superplasticity of a fine-grained Mg–1.5 wt% Gd alloy after severe plastic deformation

Document Type: Research Paper

Authors

1 School of Metallurgy and Materials Engineering, Iran University of Science and Technology

2 School of Metallurgy and Materials Engineering Iran University of Science & Technology

3 School of Metallurgical and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran

Abstract

The strain rate sensitivity (SRS) of Mg–1.5 wt% Gd processed by conventional extrusion and 2 passes of simple shear extrusion (SSE) was investigated by shear punch testing. Shear punch tests were conducted at initial shear strain rates in the range of 0.003–0.3 s-1 and at temperatures in the range of 573–773 K. A fine-grained microstructure with an average grain size of about 2.5 µm, obtained after 2 passes of SSE, resulted in high SRS index (m-value) of 0.4 at 723 K. The calculated activation energy for 2 passes deformed alloy is 116 kJ/mol which is higher than the activation energy of grain boundary diffusion in magnesium (75 kJ/mol). This higher amount of activation energy can be attributed to the presence of gadolinium in this alloy. This SRS index together with an activation energy of 116 kJ/mol are indicative of a superplastic deformation behavior dominated by grain boundary sliding accommodated by grain boundary diffusion at 723 K.

Keywords


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