SPS制备TiAl基合金微观组织演变研究

Indentification of microstructural evolution mechanisms of TiAl based alloy prepared by spark plasma sintering

摘要:

以等离子旋转电极雾化球形Ti47Al2Cr2Nb0.2W预合金粉末为原料，采用SPS技术在不同烧结温度下（1100℃、1200℃、1250℃、1300℃）制备TiAl基合金，结合XRD、SEM及TEM等检测手段，对预合金粉末致密化过程中显微组织演变进行了系统研究以及不同烧结温度对力学性能的影响。结果表明：当烧结温度超过1200℃时，组织内存在少量高温残留B2相，且随着烧结温度的升高，β相（B2相）含量有所增加；烧结温度在1100℃时合金具有最高的压缩断裂强度、拉伸断裂强度和断裂应变，分别为2367MPa、600MPa和2.25%；α2相、β相和γ相存在如下晶体学关系： ∥ ∥ ， ∥ ∥ ；1300℃烧结样品中有形变诱导α2→γ相变以及形变孪晶产生。

Abstract:

This work aims at identifying, by coupled X-Ray diffraction, scanning and transmission electron microscopy (XRD, SEM and TEM) observations, the microstructural evolution mechanisms occuring when an atomized Ti-47Al-2Cr-2Nb-0.2W powder is densified by spark plasma sintering (SPS). For this purpose, interruptions of the SPS cycle have been performed to follow the evolution of the microstricture step by step. During heating-up, the microstructure undergoes successive transformations. At begaining temperature of 1100℃ the α phase transforms into γ and residual B2. The γ phase formed is supersaturated in W. At temperature above 1200℃, TEM observations show that the repartition of the plastic dedormation is correlated to the dendritic microstructure, and the deformation induced α₂ →γ phase transformation and the twins.