Microstructural Evolution of a Fine-Grained Mg-Y-Nd Alloy during Superplastic Deformation

Abstract:

Cast Mg-4.27Y-2.94Nd-0.51Zr (wt.%) alloy was subjected to submerged friction stir processing (SFSP) with at a rotation rate of 600 rpm and a traveling speed of 60 mm min^-1. Superplastic behavior of specimens with an average grain size of ~1.3 μm were investigated in the temperature ranges of 683-758 K and the strain rate ranges from 1×10^-1 to 4×10^-4 s^-1. Microstructure characteristics were investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that the maximum elongation of 967% was obtained at 733 K and 3×10^-3 s^-1, the optimal HSRS of 900% achieved at 758 K and 2×10^-2 s^-1. Grains and second phase particles grew coarser with the increasing temperature or decreasing strain rate. Remarkable grain growth is the main reason that elongations are all significantly decreased when the strain rate decrease from 3×10^-3 s^-1 to 4×10^-4 s^-1. Grain boundary sliding is the main mechanism during superplastic deformation.

• Periodical: Materials Science Forum (Volume 849)
• Pages: 162-167
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.849.162
• Online since: March 2016
• Authors: Geng Hua Cao, Da Tong Zhang*
• Keywords: Friction Stir Processing, Mg-Y-Nd Alloy, Microstructure, Superplasticity

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