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Open AccessArticle

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

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
2
International Center of Future Science, Jilin University, Changchun 130012, China
3
Institute of Casting Research, University of Leoben, 8700 Leoben, Austria
*
Author to whom correspondence should be addressed.
Materials 2018, 11(6), 895; https://doi.org/10.3390/ma11060895
Received: 18 April 2018 / Revised: 13 May 2018 / Accepted: 23 May 2018 / Published: 26 May 2018
(This article belongs to the Section Manufacturing Processes and Systems)
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. View Full-Text
Keywords: magnesium alloy; high-ratio extrusion; aging; microstructure; tensile properties magnesium alloy; high-ratio extrusion; aging; microstructure; tensile properties
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Zhang, C.-C.; Wang, H.-Y.; Zha, M.; Wang, C.; Li, J.-H.; Yang, Z.-Z.; Jiang, Q.-C. Microstructure and Tensile Properties of AZ61 Alloy Sheets Processed by High-Ratio Extrusion with Subsequent Direct Aging Treatment. Materials 2018, 11, 895.

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