Ti1023钛合金在时效过程中的组织演化和拉伸性能

The solid solution alloy specimens were pre-aged at 250℃ and 350℃ for 5h, respectively, and then aged at 520℃ for 5h 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 1369MPa, 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%.