Ti对铸造镍基高温合金中碳化物和拓扑密排相影响

采用光学显微镜、扫描电子显微镜和透射电子显微镜等测试技术，研究了经过标准热处理和时效处理后的不同Ti含量合金的微观组织。 研究发现，标准热处理后不同Ti含量合金的相组成相同，主要由γ、γ′、MC和M23C6型碳化物组成；随着Ti含量增加，合金组织中的碳化物数量逐渐增加。 不含Ti的合金中的MC碳化物的组成主要是TaC，而含Ti合金中MC型碳化物组成为(Ta,Ti)C,并且随着Ti含量增加，MC碳化物中M组成元素Ta和Ti的比值（Ta/Ti）逐渐减小。 通过研究900 ℃不同时间时效处理后合金微观组织发现，随着Ti含量增加，合金中拓扑密排相(TCP)析出趋势逐渐增加。 含质量分数2.7%Ti的合金经900 ℃/500 h时效处理后，组织中析出了针状富含Cr、W和Mo的σ相。 这表明要保证合金具有良好的组织稳定性，需要控制合金中Ti的加入量。

Effects of Ti on Carbides and Topologically Close-Packed Phases in a High-temperature Cast Nickel-based Superalloy

In order to understand the effect of Ti on the carbides and topologically close-packed phases(TCP) in a high-temperature cast nickel-based superalloy, samples with different Ti content after heat treatment and different aging time were investigated by optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that the microstructures of as-heated alloy with different Ti content are the same and all are composed of γ, γ′, MC, and M23C6 carbides. With increasing Ti amount in the alloy, the volume fraction of carbides gradually increased. The carbide is mainly TaC when there is no Ti in the alloy, and the carbide gradually changes to (Ta,Ti)C with the addition of Ti. By examining the microstructures of alloys aged at 900 ℃ for different time, it has been found that the TCP phase segregated easily after addition of Ti in alloy. When the alloy with 2.7% mass fraction of Ti aged at 900 ℃ for 500 h, it shows that the σ phase contains a lot of Cr, W and Mo, indicating that it is necessary to control the amount of Ti in order to obtain an excellent phase stability of the alloy.