定向层片组织铸造 TiAl 合金的热等静压温度选择

摘要

The effect of hot isostatic pressing temperature on lamellar breakdown behavior and RT tensile properties was studied for a cast TiAl based alloy with directional lamellar microstructure by conventional casting,in order to optimize the temperature of hot isostat-ic pressing (HIP)for the special lamellar microstructure.After HIP at 1250 ℃,excessive equiaxed γgrains were precipitated along the colony boundary or in the colony,which resulted in reduction of tensile strength at RT.After HIP at 1290 ℃,breakdown of lamellar was occurred by coarsening of lamellar and formation of secondary lamellar with random orientation.Formation of the secondary lamellar resulted in instability of tensile properties at RT.After HIP at 1270 ℃,less equiaxed γgrains were precipitated and secondary lamellar did not generated,so the better integrality of lamellar and uniformity of lamellar orientation were kept by the microstructure obtained, and also the best tensile properties and good stability were achieved.Finally,HIP at 1270 ℃ is good for the directional lamellar micro-structure.%研究热等静压温度对定向层片组织常规铸造 TiAl 合金层片分解程度和室温拉伸性能的影响，以期优选出适于定向层片组织的热等静压温度。结果表明：在1250℃热等静压处理，析出过多的等轴γ晶粒，降低了该合金的室温拉伸强度；在1290℃热等静压处理，发生层片粗化和生成随机取向二次层片，破坏了取向一致性，降低了室温拉伸性能的稳定性。在1270℃等静压处理，等轴γ晶粒析出量较少，且未见明显的层片粗化和二次层片，所得组织保持较好的层片组织完整性和取向一致性，并表现出最佳的室温强度、塑性和性能稳定性。确定适于定向层片组织铸造 TiAl 合金的热等静压温度是1270℃。