Identification of microstructural mechanisms during densification of a TiAl alloy by spark plasma sintering
Identification of microstructural mechanisms during densification of a TiAl alloy by spark plasma sintering
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DOI：
10.1016/j.jallcom.2011.08.008
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发表时间：
2011-10
影响因子：
6.2
通讯作者：
H. Jabbar;A. Couret;L. Durand;J. Monchoux
中科院分区：
文献类型：
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作者：
H. Jabbar;A. Couret;L. Durand;J. Monchoux
本工作旨在通过扫描和透射电子显微镜(SEM)和透射电子显微镜(TEM)的耦合观察，确定雾化的Ti-47Al-1W-1Re-0.2Si粉末在放电等离子烧结(SPS)致密化过程中的致密化机理。为此，已经执行了SPS循环的中断，以逐步跟随微结构的演变。粉末颗粒具有典型的树枝晶结构，含有大量的非平衡α相。在升温过程中，显微组织经历了连续的转变。在T=525-875℃时，α相转变为γ相。形成的γ相在W和Re中过饱和。当温度高于875℃时，它通过W和富Re的B2相的不连续析出来脱饱和。T在900℃~1150℃之间通过粉末颗粒的塑性变形致密化。透射电子显微镜观察表明，塑性变形的再分配与枝晶组织有关，并存在动态再结晶机制。SPS过程中的高电流直接导致的微结构现象尚未观察到。
This work aims at identifying, by coupled scanning and transmission electron microscopy (SEM and TEM) observations, the densification mechanisms occurring when an atomized Ti–47Al–1W–1Re–0.2Si 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 microstructure step by step. The powder particles exhibit a classical dendritic microstructure containing a large amount of out-of-equilibrium α phase. During heating-up, the microstructure undergoes successive transformations. At T=525–875°C the α phase transforms into γ. The γ phase formed is supersaturated in W and Re. It de-saturates for T above 875°C by discontinuous precipitation of W and Re-rich B2 phase. Densification takes place for T between 900°C and 1150°C by plastic deformation of the powder particles. TEM observations show that the repartition of the plastic deformation is correlated to the dendritic microstructure, and that dynamic recrystallization mechanisms occur. Microstructural phenomena directly resulting from the high currents involved in the SPS process have not been observed.