TB15钛合金等温时效析出行为及相变动力学

Precipitation Behavior and Phase Transition Kinetics of TB15 Titanium Alloy during Isothermal Aging

对TB15钛合金在不同时效温度处理后的次生α相转变及动力学过程进行了研究。结果表明,TB15钛合金经β相区固溶后均为β相,经不同时效温度和时效时间处理后,随时效时间延长,α相体积分数逐渐增加,形貌由点状逐渐向针状、板条状演化,针状或板条状α相相互交织成“V”字形构型,且长时间时效后部分α相局部富集成粗大的板条状;随时效温度升高,α相体积分数先增加后降低,平均宽度逐渐增加。在相变过程中,α相转变过程可分3个阶段,即形核孕育期、快速析出期以及稳定期,在530℃时效30~60 min的快速析出阶段时效响应速度最快,硬度(HV)提升最大,提升了124。建立了TB15钛合金不同时效温度下的等温相变动力学JMAK方程,根据试验结果绘制了合金的时间-温度-转变量图(TTT图),其“鼻温”接近540℃,α相从时效开始到析出需15 min左右,时效90 min左右α相体积分数可达到最高。

The secondaryαphase transition and kinetics of TB15 titanium alloy treated with different aging temperatures were investigated.The results indicate that TB15 titanium alloy is composed ofβphase after solid solution throughβphase zone.After treatments with different aging temperature and aging time,the fraction ofαphase is gradually increased with the extension of aging time,and the morphology is transformed from dot to the needle and plate strip,which are interwoven into a"V"font configurations.After long-time aging,partial a phase are locally rich integrated into thick strip.With the aging temperature increase,the fraction ofαphase is increased firstly and then decreased,with the average size increasing gradually.Theα-phase transition process can be divided into three stages,which are nucleation incubation period,rapid precipitation period and stable period.The aging response is the fastest and hardness increment is the greatest,which reaches 124 HV,during the rapid precipitation phase aged at 530℃for 30~60 min.The JMAK equation for isothermal phase transition kinetics of TB15 titanium alloy at different aging temperatures was established,and the time-temperature-transition diagram(TTT diagram)of the alloy was plotted according to the results.The"nose temperature"of the alloy is close to 540℃,and it takes about 15 min from aging to precipitation ofαphase.The fraction ofαphase reaches the maximum value after aging for 90 min.