热处理对TLM钛合金管材组织及力学性能的影响

Influence of Heat Treatment Process on Microstructure and Mechanical Properties of TLM Titanium Tube

采用规格为Ф4.0 mm×0.3 mm冷轧TLM(Ti-25Nb-3Zr-3Mo-2Sn,TLM))合金细径薄壁管材,分别在660,720℃进行固溶处理以及对720℃固溶态管材在510℃进行时效处理,利用金相显微镜、XRD、室温拉伸及断口观察分析了固溶、时效对管材组织、力学性能的影响。不同固溶态管材均为等轴组织,随着固溶温度升高,平均晶粒尺寸增大。相变点以上的固溶组织由β相和α''相组成,相变点以下固溶组织还有少量α相。时效过程中,针状的α相在晶界析出更快,合金相变化过程为β+α''→β+α''+α→β+α,时效时间大于3 h时,α相的析出使应力-应变曲线的"双屈服"特征减弱;随着时效时间的延长,抗拉强度、屈服强度及弹性模量升高,而延伸率降低。综合分析表明:720℃+510℃,3 h时效态具有较好的综合力学性能。

An alloy with the normal composition of Ti-25Nb-3Zr-3Mo-2Sn（TLM） has been prepared using cold-rolling technology for application as a thin tube material with Φ4.0×0.3 mm. The heat treatment process has been carried out for TLM at 660 and 720 ℃; in addition,the TLM alloy with 720 ℃ solution treatment was subsequently aged at 510 ℃. The effects of heat treatment and aging process for TLM on the microstructure and mechanical properties have been investigated by metallurgical microscopy,X-ray diffraction and mechanical measurement at room temperature. Results show that the column-like crystals can be observed at any heat-treatment temperature. The average grain sizes increase with increasing temperature. The phase transition from β＋α＇＇ to α occurs in TLM. The mechanical properties depend on heat treatment temperature,due to the phase transition induced by temperature. The phase transition are dynamic,which can be described as β＋α＇＇→β＋α＇＇＋α→β＋α. The presence of α phase is beneficial for improving the tensile strength and elastic modulus and declining the elongation ratio. The preferable comprehensive property can be obtained by 720 ℃,0.5 h（ST） ＋510 ℃,3 h（AT）.