Influence of heat treatment regimes on microstructure and creep property of GH4169 alloy microalloyed by P，B

You are here: Homepage > Search

Influence of heat treatment regimes on microstructure and creep property of GH4169 alloy microalloyed by P，B

Free access

TIAN Songwen / WANG Xin / LIU Lirong / TIAN Sugui

By means of short-term aged treated （STA）, standard heat treated （ST）, long-term aged treated （LTA） and microstructure observation, the effect of heat treatment regimes on microstructure of forged GH4169 alloy is investigated. The results show that after short-term aged treated, standard heat treated and long-term aged treated, the microstructure of forged GH4169 alloy consists of γ, γ′, γ", needle-like δ-Ni3Nb phase and particle-like （Nb,Ti）C, M23C6 carbides, therein, the P element is enriched in （Nb,Ti）C phase in which the elements Cr and Mo is poor. And after STA treated, no precipitated phases are identified in the boundary regions. After standard heat treated （ST） and long-term aged treated （LTA）, there are needle-like δ phase precipitated along the grain boundaries, and the quantity and size of the one increase as the aged time prolongs. After LTA treated, the parameters of γ、γ′ and γ" phases in the alloy diminishes slightly, so that the misfits between the phases in alloy are diminished to δγ/γ′= 0.361% and δγ/γ′′= 0.128% respectively, and the misfit between γ′ and γ" phases increases to δγ′/γ′′= 0.233%. And after LTA treated, the crystallography relation between the δ and γ matrix in the alloy is maintained to be （200）γ//（110）δ and [011]γ//[001]δ, therein, the （020）δ，（\begin{document}$1\bar10 $\end{document}）δ planes of needle-like δ-Ni3Nb phase and （\begin{document}$1\bar11 $\end{document}） γ，（\begin{document}$11\bar1 $\end{document}） planes of γ matrix keep an coherent interface respectively. Compared to the LTA alloy, the STA and ST alloys display a better creep resistance. Therein, a large number of needle-like δ phase is precipitated in the LTA alloy along the boundary, which is easily to produce the stress concentration during creep, so that the cracks are easily initiated and propagated along the direction vertical to the stress axis. This is considered to be the main reason of the LTA alloy having a lower creep lifetime.