近α钛合金中次生α相转变织构的形成机制研究

The textures of the α phase frequently develop from deformation and heat treatment at various temperatures, which can cause recrystallization and phase transformation, in titanium alloys. Due to the low content of the retained β phase in near-α titanium alloys at room temperature, it is difficult to directly analyze the β crystallographic orientation of parent β grains using experimental methods. The present project carries out the following main research work based on reconstructed parent β orientation from secondary α phase: 1) the effect of β deformed texture on α-variant selection during β→α phase transformation in near α titanium alloy; 2) the influence of deformation on β texture and α-variant as well as its interaction in the formation of transformation texture. 3）the influence of β/β grain boundary, primary α grains and deformation on α-variant selection during β→α phase transformation and its effect on secondary α texture. The present research aims to present a detailed analysis of the change in texture during deformation in the α/β and β domains for a near-α titanium alloy. Specific attention is paid to the α transformation texture associated with α-variant selection.

织构是影响钛合金力学性能的一个关键因素，钛合金中次生α相的织构主要受β织构和变体选择的影响。近α钛合金在室温下β相含量较少，直接研究β相的晶体取向较困难，本项目结合次生α相的晶体取向重组原始β晶粒晶体取向方法，主要研究如下问题：1）变形β织构在次生α相变体选择中所起的作用；2）变形对β相织构和次生α相变体选择的影响及二者对α转变织构的交互作用；3）初生α相、β/β晶界和预变形等对次生α变体选择的竞争关系极其对α转变织构的影响。根据以上研究结果，探寻次生α相织构的形成机制，探讨近α钛合金中织构和微织构的形成原因，探索改善其微观组织的新工艺，为通过热加工优化近α钛合金的机械性能提供新思路。

尽管钛合金组织和织构演化的研究工作已经取得了丰富的成果，特别是关于组织控制的研究已经形成完整的体系。但针对高温钛合金晶体取向演变规律的研究还存在诸多不足，特别是对影响高温钛合金次生α相变体选择的因素和机制这一问题还没有得到根本解答。.Ti60合金是我国自主研制，可在600 °C长时使用的一种近α型高温钛合金。目前该合金已在某些型号上完成了相关实验考核并已有工程应用，是我国先进在研航空航天发动机的优选材料。.基于此，申请者拟采用Ti60合金作为研究对象，利用EBSD和β晶粒重组技术以研究不同热加工条件下近α钛合金晶体取向的演化规律为切入点，着重对以下几个命题展开探索：1）变形β织构在次生α相变体选择中所起的作用；2）变形对β相织构和次生α相变体选择的影响及二者对α转变织构的交互作用；3）初生α相、β/β晶界和预变形对次生α变体选择的竞争关系极其对α转变织构的影响。.本项目通过热加工实验得出高温钛合金次生α相变体选择受原始β晶界类型和初生α相与周围β晶粒的取向关系的双重影响，其中受初生α相与周围β晶粒的取向关系的影响较大，通过热压缩变形破坏两相间的Burgers取向关系，有助于合金微织构的消除。.以上研究可加深对高温钛合金组织和织构演变规律的理解，揭示次生α相织构的形成机制以及近α钛合金相变织构和“微织构”的形成原因，为优化高温钛合金的生产工艺提供理论依据。