合成参数对粉末冶金制备Ti3Al−11Nb−1Mo金属间化合物结构和力学性能的影响

摘要

研究了在室温和高温条件下显微组织、热处理和合金添加对Ti 3 Al基金属间化合物的力学性能和断裂特性的影响.采用机械合金化(MA)和热压(HP)方法,通过粉末冶金工艺压制Ti3Al?11Nb?1Mo(摩尔分数,%)合金.使用XRD和SEM-EDS手段表征机械合金化粉末,机械合金化的最佳时间是25 h,热压制的最佳条件是1350°C、2 h、35 MPa.合金经热压制处理后,在1050°C下固溶处理1 h,随后水淬处理,合金中存在α2+βWidmanst?tten显微组织,然而合金随后在800°C下时效24 h,诱发产生了少量O相.Mo的存在直接导致β相的含量较高.在温度从室温到750°C和真空环境下进行压缩试验,当温度升高至250°C时,压缩件的屈服强度增大(锥形滑行体系运行),随后降低.在整个温度范围内压缩件的延展性增大.在时效合金中O相的存在有助于延展性的增大,而屈服强度的降低可以忽略.相比未时效的合金,时效合金屈服强度的降低是受α2″粒子析出影响.在所有温度范围内混合断口模式都是有效的.%The influence of microstructure, heat treatment and alloying addition on mechanical and fracture properties of Ti3Al-based intermetallic at room and elevated temperatures was studied. Ti3Al?11Nb?1Mo (mole fraction, %) alloy was consolidated via powder metallurgy processing by mechanical alloying (MA) and hot pressing (HP). MA powders were characterized using XRD and SEM-EDS. Optimum MA duration was 25 h and HP conditions of 1350 °C, 2 h, 35 MPa. After HP, solution treatment at 1050 °C for 1 h and water quenchingα2+β Widmanst?tten microstructure is present, while subsequent aging at 800 °C during 24 h induces small content ofO-phase. High fraction ofβ-phase is a direct consequence of Mo. Compression tests were performed from room temperature to 750 °C in vacuum. The yield strength of compacts increases with temperature up to 250 °C (pyramidal slip systems activation), after which it decreases. Ductility increases throughout the whole temperature range. The presence ofO phase contributed to ductility increase in aged alloys, while negligibly lowering yield strength. Registered drop in the yield strength of aged alloys compared with non-aged ones was mostly influenced by precipitation ofα″2 particles. Mixed fracture modes are operative at all temperatures.