Element Segregation and Solidification Behavior of a Nb, Ti, Al Co-Strengthened Superalloy ЭК151

• 来源期刊: 金属学报（英文版）
• 年，卷（期）: 2019,（10）
• 页码范围: 1298-1308
• 页数: 11页
• 语种: 英文

摘要

The as-cast microstructure,element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated.The results show that the severe element segregation leads to the complicated precipitations at the inter-dendritic region,including η-Ni3(Ti,Nb),eutectic (γ + γ') and Laves,which shows the characteristics of both Ti,Al-strengthened and Nb-strengthened alloys.Differential thermal analysis,heating and quenching tests reveal the solidification sequence as follows:Liquids → γ matrix → (Nb,Ti)C → η-Ni3(Ti,Nb)→ eutectic (γ+ γ')→ Laves.The melting points are between 1250 and 1260 ℃ for (Nb,Ti)C,between 1200 and 1210 ℃ for η phase,between 1180 and 1190 ℃ for eutectic (γ + γ') and Laves.γ'initially precipitates from matrix at 1150 ℃ and achieves the maximum precipitation at 1130 ℃.According to the microstructure evolution captured during solidification and composition analysis by an energy dispersive spectrometer and electron probe microanalyzer,(Nb,Ti)/A1 ratio is put forward to explain the formation of η-Ni3(Ti,Nb) and eutectic (γ,+ γ').The solidification of γ,matrix increased the Nb,Ti concentration in the residual liquids,so the high (Nb,Ti)/A1 ratio would result in the formation of η-Ni3(Ti,Nb);the precipitation of the phase consumed Nb and Ti and decreased the (Nb,Ti)/Al ratio in the liquid,which led to the precipitation of eutectic (γ+ γ').Laves formed by the sides of η-Ni3(Ti,Nb) and in front of the eutectic (γ,+ γ,') after Al,Ti were further depleted by the two phases and Cr,Co,Mo were rejected to liquids.