热力耦合作用下近β钛合金α相转变机制及变体选择效应

Near β titanium alloys, such as Ti-5553, have high strength, high fracture toughness, deep hardenability, good crack propagation resistance, and improved workability camparing to α+β titanium alloy, which have been pay close attention in the field of aviation titanium alloys in recent years.The microstructure, especialy α phase evolution and resulting properties of most near β alloys are very sensitive to thermo-mechanical processing variables. However, only limited work has investigated the evolution of microstructure of near β alloys during concurrent hot deformation and phase transformation. Therefore, the present project, beased on Gleeble thermo-mechanical simulation techniques, is mainly to study the α phase evolution, variant selction and its kinetics mechnism of Ti-5553 alloy with the lammeller and globular α phase during hot deformation and subsquently heat treatment process.The work also want to clarify the mechamism of strain induced α phase tranformation, reveal the α phase variant selcetion crition, and establish the stress relaxation model which is due to phase transformation during thermo-mechinical process of near β titanium alloy. The results are believed not only to be beneficial for the in-depth understanding of the hot deformation mechanisms and phase transformation process of near β titanium alloys, but also to be veary important engineering value for optimization and controlling the microsture-properties of this kind of alloy.

以Ti-5553为代表的近β钛合金因具有高强度、高断裂韧性、良好淬透性、抗裂纹扩展性能和优异的热加工能力而成为近年航空钛合金领域关注的热点，研究热机械处理过程中相转变过程及微观组织演化规律，不仅对理解近β钛合金的变形机制至关重要，而且是实现近β钛合金组织性能调控的关键。但目前关于近β钛合金的研究多集中于热处理或热变形单一过程中的相变及组织演化，热力耦合作用对α相转变过程的影响尚不清楚。为此，本项目提出基于Gleeble热力模拟实验技术，开展"热力耦合作用下近β钛合金α相转变机制及变体选择效应"研究，阐明近β钛合金在热力耦合作用下的应力诱导α相转变过程及动力学机制，揭示正应力对α相变体选择的作用机制，建立热力耦合作用下相变导致的应力松弛模型，不仅对深入理解近β钛合金热变形机制和相转变规律具有理论意义，而且对实现该类钛合金热变形过程中的组织-性能调控、促进其应用也具有重要价值。

本项目以Ti-5553、Ti-7333合金为研究对象，基于Gleeble热-力模拟试验技术和显微组织/相结构精细表征手段，揭示了近β钛合金中β相中条纹组织的本质特征和形成机理；揭示了近β钛合金在高、低温区热力耦合作用下β→α相转变规律及α相动态演化规律，探讨了热变形对次生α相析出的影响；揭示了不同温度条件下热力耦合作用对近β钛合金β→α相转变的动力学机制，阐明了热处理、热变形对α相变体选择的作用机制；研究了不同组织近β钛合金的应力松弛行为，分析了应力松弛对α相析出和形态演的影响；初步获得了热机械处理工艺-组织-性能关系，为进一步优化近β钛合金的热机械处理工艺和性能、促进应用奠定了基础。. 国际合作方面，与法国洛林大学(Université de Lorraine)LEM3实验室在钛合金结构表征和相变机制研究方面建立了广泛而深入的合作关系，双方联合培养博士生2名（樊江昆、花珂），共同举办研讨会1次（2016年7月26-28日，西安），并在本项目基础上成功申请NSFC-CNRS(中法)国际(地区)合作与交流项目1项（No.51711530151）。. 在Acta Materialia、Scripta、Journal of Alloys and Compounds、Journal of Applied Crystallography、Materials Characterization、Materials & Design等刊物发表SCI学术13篇，申请发明专利2项。培养博士研究生4名（毕业1名，在读3名），硕士研究生5名（毕业4名，在读1名）。参加国内外学术会议13人次，做邀请报告3人次，口头报告10人次。

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