新型Ti-6554钛合金热变形行为及热加工图

Thermal Deformation Behavior and Processing Map of a New Type of Ti-6554 Alloy

利用Gleeble-1500热模拟实验机研究了新型Ti-6Cr-5Mo-5V-4Al合金在740~950℃,应变速率0.01~10.00 s^-1条件下的热变形行为。通过真应力-真应变曲线分析了合金在高温变形时的应力随温度及应变速率的变化规律,之后对数据进行回归分析得到了合金的本构方程,最后绘制合金的热加工图并结合微观组织观察研究该合金的热变形机制。结果如下:合金的流变应力对温度和应变速率都十分敏感。在相同的应变速率下,随温度升高,流变应力降低;而在相同温度下,应变速率升高,流变应力也升高。计算得到合金的动态激活能Q为246.551 kJ·mol^-1。高温变形的本构方程为ε=4.51×1010[sinh(0.0058σ)]4.85272exp(-246551/RT)。根据热加工图可知,两相区变形时,合金在温度740~770℃、应变速率0.01~0.03 s^-1的区域内具有最高的功率耗散系数,达到44%,变形机制为动态回复;β单相区变形时,在温度780~890℃、应变速率0.01~0.03 s^-1的区域内具有较高的功率耗散系数,为40%,变形机制包括动态回复和动态再结晶。合金的塑性失稳区主要在温度740~900℃、应变速率0.05~1.00 s^-1的区域内,失稳区内会发生局部塑性流动。

The hot deformation behavior of Ti-6554 alloy was investigated using Gleeble-1500 thermal simulation test machine on condition of the deformation temperature from 740 to 950℃and strain rates from 0.01 to 10.00 s^-1.The variation of flow stress with temperature and strain rate in high temperature deformation was studied by the true stress-strain curves.Through regression analysis of true stress and strain data,the constitutive equation was obtained.The hot deformation mechanism of Ti-6554 alloy was studied through the establishment of processing map and microstructural observation.The results showed that,the flow stress was sensitive to temperature and strain rate.At the same strain rate,flow stress decreased with the temperature increased,and at the same temperature,flow stress increased with the strain rate increased.Activation energy Q was equal to 246.551 kJ·mol^-1.The constitutive equation during high temperature deformation wasε=4.51×1010[sinh(0.0058σ)]4.85272 exp(-246551/RT).According to processing map,during hot deformation in two phase region,peak efficiency of power dissipation of 44%was obtained in the temperature range of 740~770℃and strain rates of 0.01~0.03 s^-1,where the deformation mechanism was dynamic recovery.During hot deformation inβphase region,high efficiency of power dissipation of about 40%was obtained in the temperature range of 780~890℃and strain rate of 0.01~0.03 s^-1,where the deformation mechanisms were dynamic recovery and dynamic recrystallization.The plastic flow instability occurring with temperatures of 740~900℃and strain rates of 0.05~1.00 s^-1 showed the plastic flow localization.