(1. 哈爾濱工業(yè)大學(xué) 金屬精密熱加工國家級重點實驗室，哈爾濱 150001；
2. 哈爾濱工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，哈爾濱 150001；
3. 中國航空工業(yè)集團公司西安飛機設(shè)計研究所，西安 710089)
摘 要: 采用XRD、SEM、TEM、常溫拉伸及蠕變等手段，對成分為Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C的新型亞穩(wěn)β鈦合金展開了研究，分析了熱處理對合金顯微組織、力學(xué)性能及蠕變行為的影響。經(jīng)過固溶時效處理后，合金的顯微組織中析出了大量針狀次生α相，次生α相與β基體保持著Burgers位向關(guān)系與半共格界面，顯著強化了合金基體，合金的最高屈服強度達到1444 MPa，同時具有4.2%的伸長率。分析蠕變實驗結(jié)果認為，蠕變斷裂是由晶界上分布的α相所引起的應(yīng)力釋放斷裂機制主導(dǎo)的。晶界α相的破碎會引入更多可能引起孔洞及裂紋產(chǎn)生的位置，使合金的抗蠕變性能惡化。因而，經(jīng)過固溶+300 ℃時效處理后，合金β晶界上α相呈連續(xù)長條狀分布，使合金具有最長的蠕變壽命。
關(guān)鍵字: 亞穩(wěn)β鈦合金；熱處理；顯微組織；拉伸性能；蠕變
（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
