一种具有TRIP/TWIP效应的高强高塑性亚稳β钛合金设计及发展

The development of new beta titanium alloys combined high strength, large ductility and improved strain-hardening behavior due to TRIP/TWIP effects

摘要:

相比不锈钢或Co-Cr合金,钛合金的低塑性以及加工硬化行为的缺失严重限制了其在高强和高塑性环境下的应用。针对这两大缺陷,本文将不锈钢中的TRIP/TWIP效应引入到β钛合金设计中,采用d-电子设计方法和控制合金电子浓度(e/a)的策略,通过控制合金的β稳定性,设计出具有TRIP/TWIP效应,极好的冷加工性能(冷轧变形率>95%),高强(抗拉强度UTS：900~1200MPa),优异塑性(均匀塑性变形能力ε~40%)和良好的加工硬化行为(加工硬化区间超过350MPa)的Ti-Mo基亚稳β钛合金。显微结构分析表明Ti-Mo基合金在塑性变形过程中产生了应力诱发马氏体相变α?和{332}<113>机械孪晶,这导致合金具有以上优异的性能。

Abstract:

Titanium and its alloys have been extensively used in numerous application fields. However, both their low ductility and their lack of work-hardening when compared with steels or Co-Cr alloys, limit their use in advanced applications where superior combinations of strength and ductility are required. Therefore, inspired from the superior mechanical properties of TRIP/TWIP steels (TRIP for Transformation Induced Plasticity and TWIP for Twinning Induced Plasticity), we proposed a new type of metastable β Ti-alloys showing combined TRIP/TWIP effects through controlling the β stability of Ti-alloys. The alloys were designed based on the “d-electron alloy design method” and controlling of electron/atom ratio (e/a). The results show that so-designed alloys display excellent combination of high strength (ultimate tensile strength ≈1020MPa), high ductility (uniform elongation 43%) and improved work-hardening behavior. The detailed microstructural analysis indicates that the superior performances arise from the synergic effects between α? phase transformation induced plasticity (TRIP) and {332}<113> twinning induced plasticity (TWIP).