超声冲击电弧增材制造钛合金零件的各向异性研究

Research on Anisotropy of Titanium Alloy Manufactured by Ultrasonic Impact Treatment and Wire and Arc Additive Manufacture

电弧增材制造钛合金构件中容易形成粗大柱状晶,导致组织和力学性能的各向异性,为了解决这一问题,拟采用超声冲击与电弧增材制造相结合来改变内部组织以实现性能的优化。研究发现,超声冲击能够使钛合金沉积层内部的粗大柱状晶转变为细小等轴晶。同时,其抗拉强度各向异性百分比由12.5%缩减为1.5%。超声冲击促进了沉积层的位错增殖及迁移,造成晶粒破碎的同时增多了形核质点。这些新增质点改变了形核环境,提高了变形储能,在后续沉积层热作用下通过回复再结晶和相变形成细小的等轴晶。

Coarse columnar grains easily form in titanium alloy during WAAM（Wire and Arc additive manufacture）, which leads to poor mechanical properties. In order to solve this problem, UIT（Ultrasonic Impact Treatment） and WAAM are combined to change the microstructure and improve the mechanical properties. It was found that UIT avoided the formation of coarse columnar grain, and transformed it to fine equiaxed grains. Meanwhile, the anisotropy percentage of UITed samples can be decreased from the 12.5% of the sample without UIT to the 1.5%. The UIT promoted the multiplication and migration of the dislocations in the deposited layers. It broke the grains, and increased the nucleus number, which changed the nucleating environment and increased deformation energy. It then changed coarse columnar grains to be equiaxed grains by recovery, recrystallization and phase transformation induced by the thermal effect of subsequent deposited layers.