固溶+时效处理对粉末冶金Ti-22Al-25Nb合金显微硬度的影响

Effect of Solution-and Aging-treatment on Microstructure and Microhardness of a Powder Metallurgy Ti-22Al-25Nb Alloy

采用放电等离子烧结技术(SPS)在950℃/80 MPa/10 min条件下制备粉末冶金Ti-22Al-25Nb(原子分数,%)合金作为初始材料,将其分别在940~1100℃、10~120 min和800℃/8 h条件下进行固溶处理和时效处理,研究了固溶+时效处理对粉末冶金Ti-22Al-25Nb(原子分数,%)合金的微观组织和显微硬度的影响,并建立了显微硬度的演变模型。结果表明,随着固溶温度的提高和保温时间的延长B2相的晶粒尺寸增大、均匀度提高,在940~1010℃晶粒长大的速率最低,在1100℃晶粒尺寸的均匀度达到最大值0.84。板条O相的尺寸和数量对合金的性能有显著影响。在(B2+O)两相区时效后,其尺寸和数量显著影响合金性能的次生板条O相的体积分数提高、尺寸减小,尤其是相互交叉、缠结的O/O相数量的增多,使合金的显微硬度提高;在1060℃/60 min/Water cooling(WC)+800℃/8 h/Furnace cooling(FC)条件下处理的合金,其显微硬度达到最大值434.92 HV。

The powder metallurgy(P/M)Ti-22 Al-25 Nb(atomic fraction,%)alloy sintered by spark plasma sintering(SPS)at 950℃/80 MPa/10 min was used as the initial material and the alloy experienced the solution treatment at the temperature range of 940~1100℃for 10~120 min and subsequently aged at 800℃/8 h.The effect of solution-and aging-treatment on the microstructure and microhardness of P/M Ti-22 Al-25 Nb alloy was investigated,while the model of microhardness evolution was proposed.The results show that the grain size and uniformity of B2 phase increase with the increase of solution temperature and holding time.The growth rate of B2 phase grain is the lowest in the temperature range of940~1010℃,and the grain size uniformity reaches the maximum 0.84 at 1100℃.The size and number of secondary lath O-phase have a significant effect on the properties of the alloy.After aging in the(B2+O)two-phase region,with the increase in the volume fraction of the secondary lath O-phase and the decrease in the size of the laths,especially the increase in the number of intersecting and entangled O/O phases,the microhardness of the alloy was enhanced.The microhardness of the alloy reached the maximum value 434.92 HV after solution and aging treatment at 1060℃/60 min/water cooling(WC)+800℃/8 h/furnace cooling(FC).