镁锡（Mg-Sn）系合金是一种极具潜力的经济耐热镁合金，但其强化相（基面析出Mg2Sn）对基面滑移阻碍弱，时效强化不明显。柱面析出相阻碍作用强，但现有的合金化或热处理对Mg2Sn取向调控不可控。本项目提出“孪生-析出-去孪生-二次析出”将Mg2Sn以特定比例调控至柱面-基面分布，有望实现强度塑性同时提高。基于此，本项目以Mg-Sn合金为研究对象，结合析出相对临界剪切应力增量的贡献模型，获得强化效果最佳的柱面Mg2Sn临界阈值，依据孪生后织构及时效硬化行为确定孪生变形及时效工艺，调控不同位向析出相在合金中所占比例，达到最佳强化效果；采用高分辨数字图像关联技术及相对位移比法研究特定位向析出Mg2Sn对基面/非基面位错的阻碍规律，结合含不同位向析出相合金的力学性能，阐明基于析出相取向的Mg-Sn合金强韧化机制。本项目提出一种构建基面-柱面组合析出相新策略，为开发高性能镁合金提供新思路及理论依据。

Mg-Sn based alloys show a great potential for the development of low-cost and heat resistant magnesium alloys. However, Mg-Sn alloy exhibits a feeble ageing strengthening because the main strengthening phase (the basal precipitated Mg2Sn) in Mg-Sn alloy shows a weak hindering effect for basal <a> dislocation. The prismatic precipitated Mg2Sn would intensely impede the basal dislocation compared to the basal precipitates. The existing methods, such as the alloying or heat treatment, could regulate the orientation of Mg2Sn to some extent, but they were uncontrollable. A novel regulating precipitate orientation method of Twinning-Precipitation-Detwinning was proposed to transfer Mg2Sn distribution from basal plane to prismatic plane in proportion so as to improve the strength and ductility simultaneously. Thus, in this project, the critical volume fraction of the prismatic precipitate, which impedes the basal dislocation to the maximum extent, will be investigated based on the developed Orowan critical resolved shear stress (CRSS) model. Then, the texture after twinning and age hardening behavior can be used to set up the twinning and ageing process parameters and further to manipulate the proportion of the basal and prismatic precipitates in Mg-Sn alloy. In addition, the advanced analysis methods of High Resolution Digital Image Correction (HRDIC) and Relative Displacement Ratio (RDR) will be applied to investigate the basal/non-basal dislocation slip behaviors for the Mg-Sn alloy containing different oriented precipitates. Finally, the mechanism that the improved the strength and ductility due to optimized precipitate orientation will be revealed via quantitative dislocation slip activity of the Mg-Sn alloy containing different oriented precipitates. The project will propose a novel strategy to build the combined basal-prismatic precipitates, and further to provide a new thought and theoretical foundation to develop high performance magnesium alloys based on precipitate orientation regulation.