(1. 哈尔滨工业大学 金属精密热加工国家级重点实验室，哈尔滨 150001；
2. 哈尔滨工业大学 材料科学与工程学院，哈尔滨 150001；
3. 中国航空工业集团公司西安飞机设计研究所，西安 710089)
摘 要: 采用XRD、SEM、TEM、常温拉伸及蠕变等手段，对成分为Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C的新型亚稳β钛合金展开了研究，分析了热处理对合金显微组织、力学性能及蠕变行为的影响。经过固溶时效处理后，合金的显微组织中析出了大量针状次生α相，次生α相与β基体保持着Burgers位向关系与半共格界面，显著强化了合金基体，合金的最高屈服强度达到1444 MPa，同时具有4.2%的伸长率。分析蠕变实验结果认为，蠕变断裂是由晶界上分布的α相所引起的应力释放断裂机制主导的。晶界α相的破碎会引入更多可能引起孔洞及裂纹产生的位置，使合金的抗蠕变性能恶化。因而，经过固溶+300 ℃时效处理后，合金β晶界上α相呈连续长条状分布，使合金具有最长的蠕变寿命。
关键字: 亚稳β钛合金；热处理；显微组织；拉伸性能；蠕变
（1. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
3. Xi''an Aircraft Design and Research Institute of AVIC, Xi’an 710089, China）
Abstract:A metastable β titanium alloy of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C was studied, and the effects of heat treatment on the microstructure, mechanical properties and creep behavior were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), room temperature tensile tests and creep tests. After solution aging treatment, a large number of acicular secondary α phases precipitate in the microstructure, while the secondary α phase keeps the Burgers relationship and the semi-coherent interface with the β matrix, which significantly strengthens the alloy. The highest yield strength of the alloy reaches 1444 MPa with the elongation of 4.2%. By analyzing the results of the creep tests, it is proposed that the creep rupture is dominated by the stress relief cracking mechanism caused by the α phase precipitating on the β grain boundary. When the grain boundary α phase is broken, there are more places for the nucleation of cavities and cracks, which deteriorates the creep resistance. Therefore, after solution-treated and aged at 300 ℃, the grain boundary α phase precipitates with continuous strip morphology, which makes this alloy has the longest creep life.
Key words: metastable β titanium alloy; heat treatment; microstructure; mechanical properties; creep
