高塑性纳米准晶Mg-1.92Zn-0.34Y合金的热变形行为

Hot Deformation Behavior of High-Ductility Mg-1.92Zn-0.34Y Alloy with Nano-quasicrystals

摘要:

纳米准晶增强Mg-Zn-Y合金室温具有超高延伸率，具有较广阔的应用前景，需进一步研究其热变形行为，为后续加工提供理论和应用基础。本工作采用半固态+热挤压的复合工艺制备了含有纳米准晶颗粒的Mg-1.92Zn-0.34Y（质量分数，下同）合金，探究本合金在250、300和350 ℃温度和10^-3、10^-2和10^-1 s^-1应变速率条件下的高温变形机制，着重研究微量纳米准晶颗粒对Mg-1.92Zn-0.34Y合金热变形行为的影响。结果表明：半固态+热挤压的复合工艺制备了高塑性纳米准晶Mg-1.92Zn-0.34Y合金，其室温下抗拉延伸率为44%±2.6%，抗拉强度为258±2.0 MPa，屈服强度为176±1.6 MPa。通过本构关系获得平均变形激活能达到271.7812 kJ/mol，其应力指数为6.7838；Mg-1.92Zn-0.34Y合金具有较好的热塑性，在研究条件下无失稳现象，表明纳米准晶颗粒能够强化其变形能力；最佳热加工区域是：330~350 ℃，10^-3~10^-2 s^-1，即高温低应变速率区。

Abstract:

The nano-quasicrystal reinforced Mg-Zn-Y alloy has ultra-high elongation at room temperature and has broad application prospects. It is necessary to further study its hot deformation behavior to provide a theoretical and application basis for subsequent processing. In this research, Mg-1.92Zn-0.34Y (wt%) alloy containing nano-quasicrystalline particles was prepared by semi-solid and hot extrusion composite process. The high temperature deformation mechanism of the alloy at temperatures of 250, 300 and 350 ℃ and strain rates of 10^-3, 10^-2 and 10^-1 s^-1 was investigated. The effect of nano-quasicrystal particles on hot deformation behavior of Mg-1.92Zn-0.34Y alloy was studied. The results show that the high-ductility Mg-1.92Zn-0.34Y alloy with nano-quasicrystals can be prepared by the combination process of semi-solid and hot extrusion. The processed alloy exhibits a high tensile elongation to failure (EL) of 44%±2.6%, ultimate tensile strength (UTS) of 258±2.0 MPa and yield strength (YS) of 176±1.6 MPa at room temperature. The average deformation activation energy and stress index of Mg-1.92Zn-0.34Y alloy according to the constitutive equation are 271.7812 kJ/mol and 6.7838, respectively. The alloy has good thermoplasticity and no instability phenomenon occurs under experimental conditions, which indicates that the presence of nano-quasicrystals improves the deformation ability of the alloy. The optimal hot working region is 330–350 ℃ and 10^-3–10^-2 s^-1, that is, the high-temperature and low strain rate region.