Exceptional grain refinement in a Mg alloy during high pressure torsion due to rare earth containing nanosized precipitates

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

卷:728

Article

Sun, W. T.¹  Qiao, X. G.¹  Zheng, M. Y.¹  He, Y.²  Hu, N.²  Xu, C.³  Gao, N.²  Starink, M. J.² 

[1] Harbin Inst Technol, Sch Mat Sci & Engn, Harbin 150001, Heilongjiang, Peoples R China

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

[3] Nagaoka Univ Technol, Dept Mech Engn, Nagaoka, Niigata 9402188, Japan

关键词: Mg-RE alloy;    High pressure torsion;    Precipitates;    Microstructure evolution;    Work hardening;   

DOI  :  10.1016/j.msea.2018.05.021

来源: Elsevier

【 摘 要 】

The influence of the nanosized rare earth (RE) containing precipitates on grain refinement during severe plastic deformation is investigated in detail through a study of high pressure torsion (HPT) processing of a solution treated and aged Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt%). In the early stages of HPT deformation, dislocation generation and pile-up is promoted by the nanosized RE containing beta' precipitates. With increasing strain, the precipitates are cut by the moving dislocations and gradually dissolve into the alpha-Mg matrix aided by dislocations serving as diffusion channels for solute atoms. After HPT for 2 turns, the hardness reaches a maximum and on further deformation the hardness decreases although the microstructure refinement continues and the dislocation density is increasing. This is due to the continuing dissolution of precipitates, which dominates the hardness evolution at this stage. After HPT for 16 turns, the precipitates have almost completely dissolved and the average grain size is similar to 33 nm, which is the smallest ever reported for a Mg- or Al-based alloy. The present peak-aged Mg8.2Gd-3.8Y-1.0Zn-0.4Zr (wt%) alloy exhibits quite different microstructure evolution and hardening behaviour during HPT processing as compared to both the cast and the solutionized Mg-Gd-Y-Zn-Zr alloy.

【 授权许可】

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