镁-铝-稀土合金中Al-RE金属间相稳定性及其对高温蠕变行为的影响研究

Mg-Al-RE系耐热镁合金在汽车等产业具有广阔的应用前景，合金中主要增强相Al11RE3是否具有高的热稳定性，即是否存在相分解，对合金高温抗蠕变性能至关重要。本项目从不同单一稀土（La、Ce、Pr、Nd）形成的Al-RE金属间相热稳定性差异出发，综合考虑稀土种类、温度、应力等影响因素，利用第一性原理计算和实验两种手段，研究Mg-Al-RE合金中不同Al-RE金属间相的热稳定性，包括相分解的过程及条件；除采用传统蠕变理论外，从微/纳观角度阐明Al-RE金属间相分解对合金蠕变抗力的影响及其机理，揭示增强相稳定性对合金抗蠕变性能的重要性，并建立合金高温蠕变变形机制。准确认识Mg-Al-RE系合金主要增强相的热稳定性及其对合金高温蠕变行为的影响，为设计新型耐热镁合金和合理使用该系合金开发汽车等耐热部件提供重要理论指导。

Mg-Al-RE heat-resistant alloys have a wide application prospect in automobile and other related fields.Whether the main strengthening phase Al11RE3 is thermally stable, namely whether the phase can decompose in the alloys, is very important for the high-temperature creep resistace.The project puts forward that the thermal stability of the Al-RE intermetallic phases varies with the kinds of the rare earth (RE=La, Ce, Pr, Nd).Taking the factors of temperature, stress and etc.into account, we use both the experiments and the first-principle calculation to study the thermal stability of the Al-RE intermetallics, including the phase decomposition conditions and process. Besides application of the traditional creep theory, we investigate the evolution of microstructure in the micro-/nano-scale during creep deformation and clarify the effect of phase decomposition on creep resistance, deeply revealing the importance of Al-RE phase stability for the heat-resistance. And finally, the creep deformation mechanism is established. In summary, it has great significances to accurately understand the thermal stability of the main strengthening phase and its effect on the creep behavior of Mg-Al-RE alloys, which can provide theoretical guidance for designing new heat-resistant magnesium alloys and rationally developing automotive transmission components.