(1. 宝鸡文理学院 机械工程学院，宝鸡 721004；
2. 西北工业大学 材料学院，西安 710072)
摘 要: 为了明确热处理时亚稳相的形成和演变对Ti1023钛合金最终组织和性能的影响，将固溶态合金样品分别在250 ℃和350 ℃预时效5 h，再在520 ℃最终时效5 h。用XRD、OM和TEM研究样品的组织演变，测试样品各阶段的拉伸性能，分析热处理对合金组织和拉伸性能的影响。结果表明：固溶空冷时形成了马氏体α″相和无热ω相；250 ℃时效时产生了稠密的等温ω相，但在β基体中没有α相形核。350 ℃时效时，α相在基体中大量形核，并形成大量细小的颗粒状α相。由于α相生长消耗ω相，350 ℃时效后，ω相数量减少，尺寸变小。ω相使预时效样品的强度升高，但是塑性降低甚至消失。固溶空冷时形成的α″相，在预时效时转变为针状α相，并最终生长为片层组织。在250 ℃预时效的最终样品中α相全部为片层组织，其拉伸强度达到1369 MPa，而在350℃预时效的最终样品中除了由α″相转变而来的片层α相，还有在时效过程中析出的长宽比为2:1的短棒状α相，这种微观组织使合金的伸长率达到8.5%。
关键字: Ti1023钛合金；α相形核；力学性能；组织演化
（1. College of Mechanical Engineering, Baoji University of Arts and Sciences, Baoji 721004, China;
2. School of Materials Science and Engineering, Northwestern Polytechnical University, Xian 710072, China）
Abstract:The solid solution alloy specimens were pre-aged at 250 ℃ and 350 ℃ for 5 h, respectively, and then aged at 520 ℃ for 5 h as final treatment in order to confirm the effect of formation and evolution of Ti1023 alloy metastable during heat treatment on the final microstructure and tensile properties. The microstructure evolution was studied by XRD, OM, and TEM, the tensile properties of specimens at each stage were tested, and the effects of heat treatment on microstructure evolution and microstructure on tensile properties were analyzed. The results indicate that the α″ and a few althermal ω phases form during cooling process after solution. The massive isothermal ω phases form, but few α phases nucleated from the β matrix during ageing at 250 ℃. Contrarily α phases nucleated largely, and grew to small α laths during aging at 350 ℃. The growth of α phase consumes the ω phases, as a result, ω phases number decreases, and the size reduces. The ω phases make the strength increase slightly and ductility decrease, even vanish. The α″ phases produced in the solution-cooling process transform to acicular α phases during pre-aging and then to lamellar structure during final ageing. The ultimate specimen pre-aged at 250 ℃ is lamellar microstructure, and the tensile strength increases to 1369 MPa, but that pre-aged at 350 ℃ show not only lamellar α phases which form from α″ phases, but also short rod-like α phases with length-width ratio of 2:1 form during aging, as a result, the elongation ratio reaches 8.5%.
Key words: Ti1023 titanium alloy; α phase nucleation; metastable phase; duplex aging
