(1. 寶雞文理學(xué)院 機(jī)械工程學(xué)院，寶雞 721004；
2. 西北工業(yè)大學(xué) 材料學(xué)院，西安 710072)
摘 要: 為了明確熱處理時(shí)亞穩(wěn)相的形成和演變對Ti1023鈦合金最終組織和性能的影響，將固溶態(tài)合金樣品分別在250 ℃和350 ℃預(yù)時(shí)效5 h，再在520 ℃最終時(shí)效5 h。用XRD、OM和TEM研究樣品的組織演變，測試樣品各階段的拉伸性能，分析熱處理對合金組織和拉伸性能的影響。結(jié)果表明：固溶空冷時(shí)形成了馬氏體α″相和無熱ω相；250 ℃時(shí)效時(shí)產(chǎn)生了稠密的等溫ω相，但在β基體中沒有α相形核。350 ℃時(shí)效時(shí)，α相在基體中大量形核，并形成大量細(xì)小的顆粒狀α相。由于α相生長消耗ω相，350 ℃時(shí)效后，ω相數(shù)量減少，尺寸變小。ω相使預(yù)時(shí)效樣品的強(qiáng)度升高，但是塑性降低甚至消失。固溶空冷時(shí)形成的α″相，在預(yù)時(shí)效時(shí)轉(zhuǎn)變?yōu)獒槧瞀料啵⒆罱K生長為片層組織。在250 ℃預(yù)時(shí)效的最終樣品中α相全部為片層組織，其拉伸強(qiáng)度達(dá)到1369 MPa，而在350℃預(yù)時(shí)效的最終樣品中除了由α″相轉(zhuǎn)變而來的片層α相，還有在時(shí)效過程中析出的長寬比為2:1的短棒狀α相，這種微觀組織使合金的伸長率達(dá)到8.5%。
關(guān)鍵字: Ti1023鈦合金；α相形核；力學(xué)性能；組織演化
（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
