中文摘要：

通过强制冷却的搅拌摩擦加工（FSP）技术在Cu—Al合金中得到了超细晶和纳米结构的微观组织，利用电子背散射衍射、透射电子显微镜等技术研究了层错能对FSP Cu-A1合金微观组织和力学性能的影响．结果表明，FSP Cu-A1合金为均匀、等轴的再结晶组织，随着层错能的减小，晶粒尺寸不断降低，而且在低层错能的FSP Cu-A1合金中，超细晶粒内部生成了丰富的纳米孪晶片层组织，进一步细化了微观组织，由于微观组织的逐步细化，FSP Cu—A1合金的强度随层错能的降低逐步提高，而均匀延伸率呈现出先增加后减小的趋势．

英文摘要：

Ultrafine-grained （UFG） and nanostructured （NS） materials have attracted considerable interest due to their special microstructure and mechanical properties. Severe plastic deformation is one of the optimum ap- proaches to fabricate bulk, dense and contamination-free UFG and NS metallic materials. However, high density of dislocations and unstable microstructure were usually induced in these UFG and NS metallic materials, resulting in poor tensile plasticity and fatigue properties. In this study, bulk UFG and NS Cu-A1 alloys were successfully pre- pared via friction stir processing （FSP） with additional forced water cooling. FSP Cu-A1 alloys exhibited uniform recrystallized microstructure with equiaxed ultrafine grains, and the grain sizes reduced gradually as the stacking fault energy （SFE） decreased. Abundant nano-twin layers formed in the ultrafine grains of FSP Cu-A1 alloys with low SFEs, which further refined the ultrafine grains and NS microstructure was achieved. The strength of the FSP Cu-A1 alloys increased clearly with decreasing the SFEs due to the gradually refined microstructure, but the uni- form elongation increased initially and then decreased in the Cu-A1 alloy with the lowest SFE.