Microstructure and Tensile Properties of AZ61 Alloy Sheets Processed by High-Ratio Extrusion with Subsequent Direct Aging Treatment

Cheng-Cheng Zhang; Hui-Yuan Wang; Min Zha; Cheng Wang; Jie-Hua Li; Zhi-Zheng Yang; Qi-Chuan Jiang

doi:10.3390/ma11060895

Microstructure and Tensile Properties of AZ61 Alloy Sheets Processed by High-Ratio Extrusion with Subsequent Direct Aging Treatment

Materials (Basel). 2018 May 26;11(6):895. doi: 10.3390/ma11060895.

Authors

Cheng-Cheng Zhang¹, Hui-Yuan Wang^{2

3}, Min Zha^{4

5}, Cheng Wang⁶, Jie-Hua Li^{7

8}, Zhi-Zheng Yang⁹, Qi-Chuan Jiang¹⁰

Affiliations

¹ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. cczhang15@mails.jlu.edu.cn.
² Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. wanghuiyuan@jlu.edu.cn.
³ International Center of Future Science, Jilin University, Changchun 130012, China. wanghuiyuan@jlu.edu.cn.
⁴ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. minzha@jlu.edu.cn.
⁵ International Center of Future Science, Jilin University, Changchun 130012, China. minzha@jlu.edu.cn.
⁶ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. chengwang@jlu.edu.cn.
⁷ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. Jiehua.Li@unileoben.ac.at.
⁸ Institute of Casting Research, University of Leoben, 8700 Leoben, Austria. Jiehua.Li@unileoben.ac.at.
⁹ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. yangzz@jlu.edu.cn.
¹⁰ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China. jqc@jlu.edu.cn.

Abstract

A high extrusion ratio of 166:1 was applied to commercial AZ61 alloy in one step with an extrusion speed of 2.1 m·min^-1. The effects of DA (direct aging) treatment on the microstructure and tensile properties of extruded alloy were investigated. The extruded alloy exhibits fine DRXed grains and the average grain size is ~11 μm. After DA treatment at 170 °C, the tensile strength and 0.2% offset yield strength is enhanced from 314 to 336 MPa and from 169 to 191 MPa respectively, sacrificing elongation from 26.5% to 23.3%. The grain size and texture distribution of extruded AZ61 scarcely evolve during the post aging treatment. However, the enhanced strength in peak-aged alloy is mainly caused by the high-density elliptical Mg₁₇Al₁₂ precipitates distributing uniformly along the grain boundaries or within the grains, by precipitation and dispersion hardening. Furthermore, the nano-sized precipitates effectively inhibit grains from coarsening by triggering pinning effects along the grain boundaries at elevated temperature. As a result, the peak-aged alloy exhibits a better superplasticity of 306.5% compared with that of 231.8% of extruded sample. This work provides a practical one-step method for mass-producing Mg alloy sheets with excellent tensile strength and ductility compared with those fabricated by conventional extrusion methods.

Keywords: aging; high-ratio extrusion; magnesium alloy; microstructure; tensile properties.