应力作用下亚稳β钛合金ω相与α相的形核机制及长大行为

Metastable β titanium alloy have been widely applied for aerospace industry owing to their high strength to density ratio, corrosion resistance, excellent fatigue/crack propagation deep hardenability. So researching effect of stress on nucleation mechanism and growth behavior of ω and αphase in metastable β titanium alloy has important practical and theoretical significance. This project intends to study on kinetics of β→ω and β→α phase transformation in Ti-1300 titanium alloy under the action of force, which is a new metastable β high strength and toughness titanium alloys developed by Northwest Institute for Nonferrous Metal Research China. And reasonable calculation model will be used to calculate energy and Avrami exponent of β→ω and β→α phase transformation in stress aging process of Ti-1300 alloy. It will be established the relationship between stress and β→ω and β→α phase transformation in Ti-1300 alloy . As well as variant selection effect of αphase in stress aging process of Ti-1300 alloy and ω role in β→α transformation process will be investigated. The effect of variant selection effect of αphase effects on the properties of Ti-1300 alloy will be studied. Finally, nucleation mechanism and growth behavior of ωand αof Ti-1300 alloy in stress aging process will be analyzed by means of TEM, SEM and EBSD. Through this research, the effect laws of stress on nucleation mechanism and growth behavior ω and α phase in metastable β titanium alloy will be summarized as far as possible, which will provide a theoretical basis for controlling microstructure of metastable β titanium alloy, performance optimization and developing process.

亚稳β钛合金因具有比强度高、耐腐蚀、好的疲劳性能和高的时效强化效应等性能在航空航天工业应用越来越广泛，因此研究应力作用下亚稳β钛合金ω相与α相的形核机制及长大行为具有重要的实际和理论意义。本项目拟研究应力作用下亚稳β钛合金Ti-1300合金中β→ω和β→α相变的动力学，并选用合理的模型计算相变激活能和Avrami指数，建立应力与β→ω和β→α相变关系；并研究Ti-1300合金在不同应力作用下时效时α相的变体选择效应和ω相在β→α相变过程中的作用，以及它们对合金性能的影响；并从微观组织角度分析应力对ω相与α相的形核机制及长大行为的影响机理。通过研究，为亚稳β钛合金的组织控制、性能优化及工艺开发提供理论依据。

亚稳β钛合金因具有比强度高、耐腐蚀、好的疲劳性能和高的时效强化效应等性能在航空航天工业应用越来越广泛，该项目以自主研发的Ti-1300合金为对象，研究了应力作用下亚稳β钛合金ω相与α相的形核机制及长大行为。选用了JMA方程计算出相变激活能和Avrami指数。同时还研究Ti-1300合金在不同应力作用下时效时α相的变体选择效应以及对合金性能的影响；从微观组织角度分析应力对ω相与α相的形核机制及长大行为的影响机理。研究结果表明：20MPa压应力作用下Ti-1300合金的ω相变的平均激活能为73KJ/mol，高于自由时效的平均相变激活能（55KJ/mol）。在连续加热转变中，随ω相转变量增加而相变激活能逐渐减小。在3℃/min加热速率条件下，随着应力的增加，固溶态Ti-1300合金β相基体中析出的ω相更加密集，而ω相形貌没有明显变化；合金最终析出的α相逐渐由颗粒状变为短针状，且针状α相的择优取向效应也越来越明显。在双重应力时效时，合金组织中针状α相较双重自由时效时出现了择优取向效应，且针状α相的长宽比明显增加；合金低温应力时效然后高温自由时效别低温自由时效然后高温应力时效所获组织更加弥散均匀。