摘要
The hot deformation characteristics of as-forged Ti−3.5Al−5Mo−6V−3Cr−2Sn−0.5Fe−0.1B−0.1C alloy within a temperature range from 750 to 910℃and a strain rate range from 0.001 to 1 s^(-1) were investigated by hot compression tests.The stress−strain curves show that the flow stress decreases with the increase of temperature and the decrease of strain rate.The microstructure is sensitive to deformation parameters.The dynamic recrystallization(DRX)grains appear while the temperature reaches 790℃at a constant strain rate of 0.001 s^(-1) and strain rate is not higher than 0.1 s^(-1) at a constant temperature of 910℃.The work-hardening rateθis calculated and it is found that DRX prefers to happen at high temperature and low strain rate.The constitutive equation and processing map were obtained.The average activation energy of the alloy is 242.78 kJ/mol and there are few unstable regions on the processing map,which indicates excellent hot workability.At the strain rate of 0.1 s^(-1),the stress−strain curves show an abnormal shape where there are two stress peaks simultaneously.This can be attributed to the alternation of hardening effect,which results from the continuous dynamic recrystallization(CDRX)and the rotation of DRX grains,and dynamic softening mechanism.
通过热压缩实验研究Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C锻态合金在750~900℃温度范围和0.001~1 s^(-1)应变速率范围内的热变形特征。应力-应变曲线表明,流变应力随着温度的提高和应变速率的降低而降低。显微组织对热变形参数十分敏感,当应变速率保持在0.001 s^(-1)不变,温度达到790℃或者温度保持在910℃不变,应变速率不高于0.1s^(-1)时合金显微组织中出现动态再结晶晶粒。计算出加工硬化率θ,并发现动态再结晶倾向于在较高温度和较低应变速率条件下发生。得到合金的本构方程和加工硬化图,平均热激活能为242.78 k J/mol,而且只有少量失稳区在热加工图中出现,说明合金具有良好的热加工性能。当应变速率为0.1s^(-1)时,应力-应变曲线呈现一种异常的形状,连续出现两个应力峰值,这一现象可以归因于连续动态再结晶和再结晶晶粒的转动所造成的硬化现象与动态软化机制的混合作用。
