拉伸变形诱导Ti-6Al-4V钛合金相转变机制

Phase transformation mechanism of Ti-6Al-4V titanium alloy induced by tensile deformation

钛合金中的相转变行为对材料的塑性变形以及力学性能起到至关重要的影响。因此,有必要深入研究钛合金的相转变行为,并在此基础上揭示相转变的机制。采用一种新颖的热处理工艺成功在Ti-6Al-4V钛合金中引入细β晶马氏体组织。发现在拉伸载荷条件下存在变形诱导HCP相向FCC相转变的行为,并揭示了相转变机制。HCP相与新形成的FCC相之间满足晶体学取向关系:■。通过两相之间的晶体学取向关系提出相转变机制:HCP相(0001)晶面上每两个原子层之间的一个■肖克莱不全位错滑移。通过第一性原理计算HCP相向FCC相转变过程中■层错能变化,成功验证了该相转变机制。

Phase transition behavior plays a crucial role on the plastic deformation and mechanical properties of titanium alloy.Therefore,it is very necessary to study the phase transition behavior and further reveal the corresponding mechanism of titanium alloy.In this paper,a novel heat treatment process was successfully used to introduce a fine β grain martensite structure into Ti-6Al-4V titanium alloy.Deformation-induced HCP phase to FCC phase transition behavior under tensile loading conditions was discovered,and the corresponding phase transition mechanism was revealed.The crystallographic orientation relationship between the HCP phase and the newly formed FCC phase is:■.The phase transition mechanism is proposed based on the crystallographic orientation relationship between the two phases:■type Shockley partial dislocations slip on every two (0001) atomic basal planes.This phase transition mechanism was further verified by first principles that calculated the change of ■stacking fault energy during HCP to FCC phase transition.