粉末冶金Ti-22Al-25Nb合金的放电等离子烧结工艺数值模拟与实验研究

选用Ti-22Al-25Nb预合金粉末为实验初始原料，采用放电等离子烧结工艺（SPS）制备组织致密的粉末冶金Ti-22Al-25Nb合金。采用MSC.Marc有限元软件对SPS过程中粉末的致密化过程进行了数值模拟，分析了烧结温度、保温时间和烧结压力对粉末致密化过程的影响，揭示了粉末相对密度随烧结温度、保温时间和烧结压力的变化规律。根据模拟结果，在950~1 200 ℃温度区间、50 MPa烧结压力和10~20 min保温时间的条件下，完成系列SPS烧结实验，制备获得Ti-22Al-25Nb合金。系统分析了50 MPa/10 min烧结条件下温度对Ti-22Al-25Nb合金的相对密度、显微组织和力学性能的影响，揭示了烧结合金的断裂机制。实验结果表明烧结合金在950 ℃/50 MPa/10 min条件下具有最优的综合力学性能，延伸率和屈服强度分别达到8.14%和691.04 MPa。

Numerical Simulation and Experimental Study on SPS Processes for a Powder Metallurgy Ti-22Al-25Nb Alloy

A Ti-22Al-25Nb alloy with dense microstructure was prepared by using SPS method from pre-alloy powders. The densification of the powders during the SPS processes was simulated numerically by using the finite element software MSC. Marc. The effects of sintering temperature， holding time and sintering pressure on the densification processes of the Ti-22Al-25Nb powders were analyzed， respectively. The evolutions of relative density varying with sintering temperature， holding time and sintering pressure were revealed， respectively. Based on the results of simulation， the temperature range of 950~1 200 ℃， 50 MPa pressure and 10~20 min holding time were utilized in a series of sintering experiments to fabricate the Ti-22Al-25Nb alloys. The effects of temperature on the relative density， microstructure evolution and mechanics property of Ti-22Al-25Nb alloy at 50 MPa /10 min were systematically revealed. In addition， the fracture mechanism of the alloys sintered at different temperatures was revealed， respectively. The results show that the alloys sintered at 950 ℃/50 MPa/10 min exhibit a better mechanics property with the elongation of 8.14% and the yield stress of 691.04 MPa.