TB6钛合金两相区变形行为及组织演变规律

Deformation behavior and microstructure evolution law of two-phase region for TB6 titanium alloy

通过对TB6钛合金棒料进行不同参数下的热模拟压缩实验,得到了TB6钛合金的真应力-真应变曲线,并对比分析了等效应变为0.9时,不同变形温度(700~790℃)和应变速率(0.001~1s^(-1))下TB6钛合金两相区的组织演变规律以及一定变形条件下(760℃、0.1s^(-1))的再结晶行为。结果表明:变形温度过高会导致α相向β相转变的数量增多,变形温度以700~760℃为宜;流动应力与应变速率呈正相关,流动应力的增加延缓了动态回复和动态再结晶动力学过程,不利于锻件的精确塑性成形,应变速率以0.001~0.1s^(-1)为宜;变形量的增加可促使长条状α相发生再结晶球化转变为等轴状晶粒,却不利于合金的韧性,变形量以40%左右为宜。变形温度为760℃、应变速率为0.1s^(-1)条件下,大、中、小3种角度晶界占比分别约为8.6%、31.7%和59.8%,α相、β相的再结晶分数分别约为14.8%和4.99%,在某些方向上两种晶粒结构均表现为较强的织构;TB6钛合金两相区热变形的失稳区主要集中于变形温度为700~760℃、应变速率为0.01832~1s^(-1)的区域,进一步地绘制了相应的热加工图。

The true stress-true strain curve of TB6 titanium alloy was obtained by conducting thermal simulation compression experiments with different parameters on TB6 titanium alloy bars,and the microstructure evolution law of the two-phase region for TB6 titanium alloy under different deformation temperatures (700-790℃),strain rates (0.001-1 s^(-1)),and the recrystallization behavior under certain de-formation conditions (760℃,0.1 s^(-1)) were compared and analyzed when the equivalent stain was 0.9.The results show that excessive deformation temperature leads to an increase in the number of α to β phase transition,and the appropriate deformation temperature is700-760℃.The flow stress is positively correlated with the strain rate,and the increasing of flow stress delays the kinetic process of dy-namic recovery and dynamic recrystallization,which is not conducive to the precise plastic forming of forgings.The appropriate strain rate is 0.001-0.1 s^(-1).The increasing of deformation amount can promote the recrystallization and spheroidization of the elongated α phase into the equiaaxial grain,but it is not conducive to the toughness of alloy,and the appropriate deformation amount is about 40%.Under the conditions of the deformation temperature of 760℃and the strain rate of 0.1 s^(-1),the proportion of large,medium and small angle grain boundaries is about 8.6%,31.7%and 59.8%,respectively.The recrystallization fractions of α and β phases are about 14.8%and4.99%,respectively.In some directions,both grain structures exhibit strong texture.The unstable region of thermal deformation for TB6titanium alloy two-phase region is mainly concentrated in the region with the deformation temperature of 700-760℃and the strain rate of0.01832-1 s^(-1),and the corresponding thermal processing diagrams are drawn further.