Zhang Cheng-Cheng, Wang Hui-Yuan, Zha Min, Wang Cheng, Li Jie-Hua, Yang Zhi-Zheng, Jiang Qi-Chuan
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.
International Center of Future Science, Jilin University, Changchun 130012, China.
Materials (Basel). 2018 May 26;11(6):895. doi: 10.3390/ma11060895.
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. 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 MgAl 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.
以2.1 m·min的挤压速度对商用AZ61合金一步施加166:1的高挤压比。研究了直接时效（DA）处理对挤压合金微观结构和拉伸性能的影响。挤压合金呈现出细小的动态再结晶晶粒，平均晶粒尺寸约为11μm。在170°C进行DA处理后，拉伸强度和0.2%规定非比例延伸强度分别从314 MPa提高到336 MPa，从169 MPa提高到191 MPa，伸长率从26.5%降至23.3%。挤压态AZ61的晶粒尺寸和织构分布在时效后处理过程中几乎没有变化。然而，峰值时效合金强度的提高主要是由于高密度的椭圆形MgAl析出相沿晶界或晶粒内均匀分布，通过析出和弥散强化作用。此外，纳米级析出相通过在高温下触发沿晶界的钉扎效应，有效地抑制了晶粒粗化。结果，峰值时效合金表现出比挤压态样品更好的超塑性，分别为306.5%和231.8%。这项工作提供了一种实用的一步法，相比传统挤压方法制备的镁合金板材，能够大规模生产具有优异拉伸强度和延展性的镁合金板材。
