SPS烧结温度对Ti-45Al-8Nb合金组织及力学性能影响研究

Microstructure and mechanical properties of Ti?45Al?8Nb alloy sintered at different SPS temperatures

摘要:

本文以雾化法制备的Ti-45Al-8Nb (at.%) 预合金粉末为原料,采用放电等离子烧结工艺技术(SPS)制备了Ti-45Al-8Nb合金,研究了不同烧结温度对合金显微组织及力学性能的影响规律。实验结果表明,在烧结温度范围内(1250℃、1275℃、1300℃),合金均为全片层组织,并具有高抗压强度和压缩率。随着烧结温度的提高,合金中γ相含量升高,α₂相含量下降。1250℃放电等离子烧结时,合金中并未出现B2相,随着烧结温度的升高,合金中的B2相主要由晶界析出,并呈增多的趋势。分析表明,主要是由于放电等离子烧结过程中使得粉末间产生局部高温形成液相,其后的快速凝固导致高温β相来不及转变而形成的B2相残留。合金总体表现出随着烧结温度的升高,合金的强度和塑性性能下降的趋势。SPS烧结温度为1250℃时,抗压强度和压缩率最佳,分别为2084.20MPa和33.10%。合金SPS烧结温度为1250℃和1275℃时,断裂模式主要为沿片层断裂和穿片层断裂混合方式。SPS烧结温度为1300℃时,断裂则主要以沿片层断裂为主。

Abstract:

In this paper, TiAl alloys with a nominal composition of Ti-45Al-8Nb (at.%) were prepared by spark plasma sintering (SPS) process. The effect of sintering temperatures on microstructure and mechanical properties of Ti-45Al-8Nb alloy has been studied. The results show that the microstructures of Ti-45Al-8Nb alloy sintered at different temperatures all exhibit full lamellae structure. With the increasing of sintered temperature, the amount of γ phase in the alloy increases and α₂ phase decreases. There is no B2 Phase when sintered at 1250℃. As the sintering temperature increases, the B2 phase precipitates at the grain boundary and the amount of B2 phase increases. The main reason is that the alloy may melt at local areas with the increasing of sintering temperature; the β phase would order to B2 phase at high cooling rates. The tensile strength and compression ratio decreases with the sintering temperature increasing from 1250℃ to 1300℃. The maximum tensile strength and compression ratio reached 2084.20MPa and 33.10% at 1250℃ respectively.