近β钛合金冷变形纳米化及后续时效组织演变机制和力学行为研究

Severe cold plastic deformation inducing nano-structure is one kind of high efficient strengthening method. To explore potential mechanical property of near β titanium alloy, one kind of typical near β titanium alloy, i.e., Ti-10V-2Fe-3Al (Ti-1023), will be selected as the research material. Nano structure Ti-1023 will be obtained by compressing solution treated Ti-1023 alloy under room temperature. During this process, systematic investigations will be carried out on the deformation response, microstructure evolution and grain refinement mechanism. A thermodynamic model of this structure evolution will be established, which will help to reveal the relationship between the cold deformation parameters and microstructures in this type of alloys. To enhance the comprehensive mechanical properties of this kind of alloys, subsequent aging treatment will be applied to the nano structure Ti-1023 alloy. The structure evolution and the corresponding mechanical behaviors during aging treatment will be fully studied. A strength model will be established on aging treated nano structure Ti-1023 alloy, revealing strengthening and toughening mechanisms in this kind of alloys subjected to cold deformation. This research will not only help to understand the strengthening and toughening mechanisms in cold deformed and ageing treated near β titanium alloys, but also provide a new method to strengthening and toughening this kind of alloys.

强烈塑性冷变形致晶粒纳米化是一种有效的金属材料强化途径。为了发掘近β钛合金的力学潜能，本项目选择一种典型的近β钛合金Ti-10V-2Fe-3Al (Ti-1023)作为研究对象，采用对固溶态冷压变形的方法，获得纳米化组织，系统地研究冷变形过程中的组织变形响应、演化规律及晶粒细化机制，建立冷变形过程中组织演化的热力学模型，揭示该类合金晶粒细化程度与冷变形参数之间的内在联系，同时对冷变形纳米化后的合金进行时效处理以进一步提高综合性能，系统研究时效过程中的组织演化及相应的力学性能，建立冷变形纳米化后时效—强度本构模型，从理论上揭示时效处理对该类合金冷变形纳米化组织的力学性能的影响机理。该项研究将有助于全面深入地理解近β钛合金冷变形纳米化机制及后续时效处理的强韧化机理，而且可为此类合金的强韧化提供一种新的技术途径。

剧烈冷变形因其具有强大的晶粒细化能力，可以使很多金属和合金的内部组织细化至亚微米级甚至纳米级的超细晶材料，因而收到了广泛的关注。本项目系统研究了钛合金在塑性变形过程中的组织响应及力学性能，主要研究结果如下：1.对完全固溶的TB6合金进行不同应变量的变形，结果表明合金的细化归结为应力诱发马氏体相变的分割作用以及剪切带的形成和扩展, 基于变形后的组织，考虑到各相组织对强度的贡献，建立了变形后组织强度预测的理论模型，其结果与实测值符合的较好；2.研究了变形对TB6合金双相区固溶组织和力学性能的影响, 结果发现，与α相相比，β相细化趋势要明显得多，出现了大片的纳米晶区。β相更快、更有效的细化归结于应力诱发马氏体α″对β相的分割作用和随后剪切带的形成及扩展，而较小的α相尺寸产生的强化效应及变形细化所需极高的位错密度使得α相在整个变形过程中没有得到有效细化；3.研究了变形对单相α组织钛合金Ti-2.5Cu的变形组织及力学性能的影响, 结果显示时效之前先进行预应变引入的高密度位错可以充当高效的扩散通道，从而加快Ti2Cu粒子的析出及长大动力学过程,在考虑了α 钛合金滑移变形特征的基础上，基于Orowan机制首次推导出了Ti-2.5Cu合金时效析出强化模型, 其计算结果能够较好的预测时效状态该合金强度随时效时间的变化规律。