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通过恒应变速率超塑性拉伸试验,研究了TC21钛合金在变形温度为1 153~1 193K,应变速率为3.3×10-4~3.3×10-2 s-1条件下的拉伸流变应力行为。计算了TC21钛合金超塑性拉伸变形激活能和相应的应力指数,建立了TC21钛合金应力-应变本构模型,并通过1stopt软件对其进行修正。研究表明,在同一应变速率下,TC21钛合金流变应力随变形温度的升高而减小;在同一变形温度下,流变应力随着应变速率的增大而增大。当应变速率较高,变形温度较低时,动态再结晶为主要软化机制;当应变速率较低,变形温度较高时,加工硬化与软化达到动态平衡,软化机制以动态回复为主;当变形温度为1 153K,应变速率为3.3×10-4 s-1时,TC21钛合金具有较好的超塑性(408.60%);超塑性拉伸变形激活能和应力指数分别为329.20kJ/mol、2.367 7。
Through constant strain rate superplastic tensile test, the tensile flow stress of TC21 titanium alloy under the conditions of deformation temperature of 1 153-1 193K and strain rate of 3.3 × 10-4 ~ 3.3 × 10-2 s-1 behavior. The activation energy of tensile deformation and the corresponding stress index of TC21 titanium alloy were calculated. The stress - strain constitutive model of TC21 titanium alloy was established and modified by 1stopt software. The results show that the flow stress of TC21 titanium alloy decreases with the increase of the deformation temperature at the same strain rate. At the same deformation temperature, the flow stress increases with the increase of the strain rate. When the strain rate is higher and the deformation temperature is lower, the dynamic recrystallization is the main softening mechanism. When the strain rate is lower and the deformation temperature is higher, the work-hardening and softening reach the dynamic equilibrium, and the softening mechanism is dominated by dynamic recovery. TC21 titanium alloy has a good superplasticity (408.60%) at a temperature of 1 153K and a strain rate of 3.3 × 10-4 s-1. The activation energy and stress exponent of superplastic tensile deformation are 329.20kJ / mol and 2.367 7.