微量Ni对增材制造新型钛合金的组织演变和强韧化的影响机制研究

利用强共析元素Ni可将增材制造钛合金的粗大柱状晶转变为细小等轴晶，但共析产物Ti2Ni会损害钛合金的塑韧性。利用选择性激光熔化（SLM）技术，在含微量Ni (0.4 wt.%)的新型Ti-Ni合金中可获得高强韧马氏体组织。本项目拟研究微量Ni对SLM Ti-Ni组织演变的影响规律，探索过饱和固溶Ni的调控极限和Ti-Ni的强韧化极限。揭示Ni含量和Ni偏聚对钛合金马氏体相变的影响机制和超细化马氏体的形成机制。研究微量Ni在钛合金中的强韧化效果，探索过饱和固溶Ni的强化极限、及其对位错运动和孪生行为的影响机制，探索超细化晶粒对强韧性的提升规律，探索回火马氏体中Ti2Ni析出的强化效果。最终提出增材制造新型钛合金的Ni微合金化原理，及其组织性能调控原理，为制备高强韧钛合金探索新途径。

Eutectoid forming elements, Ni, which could turn coarsen columnar crystal into equixed fine grains. But could generate brittle Ti2Ni and lower ductility and toughness. High strength-tough nickel-microalloyed titanium was produced by selective laser melting and obtained martensitic microstructure. This project was proposed to study the microstructural evolution of the nickle-microalloyed titanium, and explore the limitation of solubility of nickel in titanium and best mechanical properties of titanium alloy. Study the influences of Ni content and Ni segregation on the martensitic transformation, and reveal the refining mechanism of nickle-microalloyed titanium. Study the effect of Ni for the improvement of strength and toughness. Explore the solution strengthening of Ni and precipitation strengthening of Ti2Ni. Study the influences of Ni for the motion of dislocation and twinning is α’-Ti. Developing a new microalloying theory for the additive manufacturing of titanium alloys, developing tailoring method of the microstructure and mechanical properties, and find a pathway for a new kind of high strength-tough titanium alloy.