TB8钛合金形变诱导超塑性成形技术研究

发布时间：2018-06-07 00:23

  本文选题：TB8钛合金 + 超塑性　； 参考：《南昌航空大学》2017年硕士论文

【摘要】：TB8钛合金是一种超高强度亚稳态β型钛合金,常用于制备航空、航天领域的结构件。较高的β稳定元素含量使得该合金的变形抗力较高,导致在塑性成形工艺的应用中受到限制。因此,探讨该合金超塑性成形技术成为解决这一问题的有效途径之一。本文以热变形参数对TB8钛合金动态再结晶及时效析出行为的影响为切入点,从热变形过程中的动态再结晶、时效析出行为等多个角度研究了TB8钛合金超塑性行为以及超塑性变形过程中的组织演变规律。同时引入形变诱导超塑性拉伸法,通过形变诱导析出强化和再结晶组织优化双重手段有效地提高其超塑性能。通过高温拉伸试验研究TB8钛合金超塑性变形显微组织的演变及变形条件对超塑性变形行为的影响。结果表明:在变形温度为690℃~840℃、应变速率为10-4s-1~10-3s-1拉伸时,TB8钛合金具有超塑性变形性能,且在750℃、10-4s-1变形条件下,延伸率最大为524.9%。变形过程中,变形软化和加工硬化相互抵消,表现为传统的超塑性变形稳态流动特征;同时,变形温度、应变速率和变形程度对超塑性变形后的显微组织有显著的影响,随着变形速率的降低,等轴β相晶粒尺寸增大;随着变形温度的升高,β相晶粒尺寸增大,并伴有α相到β相的转变,但仍能保持一定的等轴度;随着变形程度的增大,β晶界和基体弥散析出的α相越多,细小、弥散分布的α相可以抑制晶粒的过分长大。采用形变诱导法对TB8钛合金进行了超塑性拉伸试验,研究了变形温度、预变形量和中间保温时间对该合金超塑性性能及微观组织演变的影响。结果表明:与恒应变速率法拉伸相比,该方法拉伸后合金的超塑性得到大幅度地提升,变形温度为750℃、预变形量为50%和保温时间为20min时,该合金的超塑性能最好,延伸率为796.1%。预变形阶段,脱溶析出和再结晶双重优化作用使亚稳态β相转变为细小均匀的再结晶组织,在后续变形过程中,细小弥散的α相既能抑制再结晶晶粒过分长大,又能在一定程度上使再结晶组织发生应变集中而破碎。超塑性变形后合金的微观组织仍然保持较好的等轴状,具有显著的超塑性变形特征。通过对TB8钛合金热变形行为研究,建立了合金的动态再结晶有关模型。分析得到随着变形温度的升高和应变速率的减小,发生动态再结晶体积分数增加,再结晶晶粒尺寸随之增加;而低温和高应变速率环境下则会延迟动态再结晶的发生。合理控制热变形参数,可以得到均匀细小的动态再结晶组织,提高合金的塑性变形能力,所得结论与试验结果相吻合。
[Abstract]:TB8 titanium alloy is a super high strength metastable 尾-titanium alloy. The high content of 尾 -stable elements makes the alloy have higher deformation resistance, which limits its application in plastic forming process. Therefore, discussing the superplastic forming technology of the alloy is one of the effective ways to solve this problem. Based on the effect of thermal deformation parameters on dynamic recrystallization and aging precipitation behavior of TB8 titanium alloy, the dynamic recrystallization during hot deformation is studied in this paper. The superplastic behavior and microstructure evolution of TB8 titanium alloy during superplastic deformation were studied from aging precipitation behavior. At the same time, the deformation induced superplastic tensile method was introduced to improve the superplasticity effectively by means of deformation induced precipitation strengthening and recrystallization microstructure optimization. The evolution of superplastic deformation microstructure of TB8 titanium alloy and the effect of deformation conditions on superplastic deformation behavior were studied by high temperature tensile test. The results show that TB8 titanium alloy has superplastic deformation property when the deformation temperature is 690 鈩，

本文编号：1988805