Precipitation Kinetic Analysis for δ Phases at Grain Boundary of GH4169 Alloy

GH4169 alloys which were solution treated and deformed at high temperature were conducted on aging treatment to investigate the morphology and precipitation mechanisms of δ phases. The results show that the volume fraction of δ phases increases with the increase of Nb element content. The peak temperature for δ phases precipitation is 920℃ which is slightly influenced by the content of Nb element. The nucleation rate and volume fraction of δ phases increase with the decreasing of average grain size. Otherwise, the size of δ phases decreases with the decrease of average grain size. Low angle grain boundaries within grains promote the precipitation of δ phases intergranular. The critical barrier and critical radius decreases with the decrease of the radius of curvature. Otherwise, the nucleation rate of δ phases increases with the decreasing of curvature. The distribution morphologies of δ phases precipitated at grain boundary are similar to needles, sawteeth and fish tails.