Cryogenic treatment is an effective method that can improve the material's performance by changing the microstructure, such as shrinking the crystal lattice. It is usually used in combination with the annealing treatment of the material. In this article, the effects of cryogenic and annealing treatment on the microstructure and mechanical properties of TA15 friction stir welded joints are investigated. The results show that the base material's microstructure has no noticeable change after cryogenic and annealing treatment. However, the microstructure of the stirred zone has an apparent structural transformation. It indicates a selected influence of cryogenic and annealing treatment on the microstructure under severe plastic deformation of the friction stir welding. The weight fraction of the α phase increases from 78.7% to 84.8%, and the aspect ratio of the β phase becomes smaller. These changes improve the mechanical properties of the friction stir welded joints. The ultimate tensile strength and elongation of the TA15 welded joints treated by cryogenic and annealing treatment are 943.4 MPa and 5.5%.

低温处理是一种有效的方法，可以通过改变微观结构（例如收缩晶格）来提高材料的性能。通常将其与材料的退火处理结合使用。本文研究了低温和退火处理对TA15搅拌摩擦焊接接头组织和力学性能的影响。结果表明，经低温退火处理后，基体材料的微观结构无明显变化。然而，搅拌区的微观结构具有明显的结构转变。这表明在搅拌摩擦焊接严重塑性变形下，低温和退火处理对显微组织有选择的影响。α相的重量分数从78.7％增加到84.8％，β相的纵横比变小。这些变化改善了搅拌摩擦焊接接头的机械性能。经过低温和退火处理的TA15焊接接头的极限抗拉强度和伸长率分别为943.4 MPa和5.5％。