Superplasticity of a nano-grained Mg-Gd-Y-Zr alloy processed by high-pressure torsion

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:651

Article

Alizadeh, R.^1,2  Mahmudi, R.¹  Ngan, A. H. W.²  Huang, Y.³  Langdon, T. G.³ 

[1] Univ Tehran, Coll Engn, Sch Met & Mat Engn, Tehran, Iran

[2] Univ Hong Kong, Dept Mech Engn, Pokfulam, Hong Kong, Peoples R China

[3] Univ Southampton, Fac Engn & Environm, Mat Res Grp, Southampton SO17 1BJ, Hants, England

关键词: High-pressure torsion;    Mg-Gd-Y-Zr alloys;    Nano-grained metals;    Shear punch testing;    Superplasticity;   

DOI  :  10.1016/j.msea.2015.10.094

来源: Elsevier

【 摘 要 】

While most of the reports on Mg-Gd-Y-Zr alloys report superplasticity after extrusion or friction stir processing, it is important to investigate superplasticity in these alloys after other severe plastic deformation processes having greater grain refinement capability. Accordingly, superplasticity was studied in an Mg-9Gd-4Y-0.4Zr (GW94) alloy after different high-pressure torsion (HPT) conditions. The HPT was performed at room temperature under an applied pressure of 6.0 GPa for up to 16 turns. TEM microstructural characterization revealed that the grain size was reduced from an initial value of similar to 8.6 mu m in the extruded condition to similar to 95 +/- 10 and similar to 85 +/- 10 nm after 8 and 16 turns, respectively. A shear punch testing method was used for evaluation of superplasticity at 573, 623, 673 and 723 K. Maximum strain rate sensitivities of similar to 0.51 +/- 0.05 and similar to 0.48 +/- 0.05 were obtained at 623 K for the material processed through 16 and 8 turns, respectively. This strain rate sensitivity and an activation energy of similar to 100 +/- 5 kJ mol(-1) suggests the occurrence of grain boundary sliding in the superplastic region. (c) 2015 Elsevier B.V. All rights reserved.

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