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Microstructural Evolution and Mechanical Properties in Superlight Mg-Li Alloy Processed by High-Pressure Torsion

1,2, 1,2,*, 1,2, 3, 1,2, 1,2 and 3,*
1
Key Laboratory of Micro-Systems and Micro-Structures Manufacturing of Ministry of Education, Harbin Institute of Technology, Harbin 150080, China
2
School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
3
Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, South Korea
*
Authors to whom correspondence should be addressed.
Materials 2018, 11(4), 598; https://doi.org/10.3390/ma11040598
Received: 3 March 2018 / Revised: 29 March 2018 / Accepted: 3 April 2018 / Published: 13 April 2018
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

Microstructural evolution and mechanical properties of LZ91 Mg-Li alloy processed by high-pressure torsion (HPT) at an ambient temperature were researched in this paper. The microstructure analysis demonstrated that significant grain refinement was achieved after HPT processing with an average grain size reducing from 30 μm (the as-received condition) to approximately 230 nm through 10 turns. X-ray diffraction analysis revealed LZ91 alloy was consisted of α phase (hexagonal close-packed structure, hcp) and β phase (body-centered cubic structure, bcc) before and after HPT processing. The mean value of microhardness increased with the increasing number of HPT turns. This significantly increased hardness of specimens can be explained by Hall-Petch strengthening. Simultaneously, the distribution of microhardness along the specimens was different from other materials after HPT processing due to the different mechanical properties of two different phases. The mechanical properties of LZ91 alloy processed by HPT were assessed by the micro-tensile testing at 298, 373, 423, and 473 K. The results demonstrate that the ultra-fine grain LZ91 Mg-Li alloy exhibits excellent mechanical properties: tensile elongation is approximately 400% at 473 K with an initial strain rate of 1 × 10−2 s−1. View Full-Text
Keywords: microstructure; mechanical property; ultrafine-grains; high-pressure torsion; Mg-Li alloys microstructure; mechanical property; ultrafine-grains; high-pressure torsion; Mg-Li alloys
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Su, Q.; Xu, J.; Li, Y.; Yoon, J.I.; Shan, D.; Guo, B.; Kim, H.S. Microstructural Evolution and Mechanical Properties in Superlight Mg-Li Alloy Processed by High-Pressure Torsion. Materials 2018, 11, 598.

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