Kinetics of δ phases precipitated at grain boundaries during aging of GH4169 superalloy

Abstract:

GH4169 alloy is a Ni-Fe based superalloy which is used as the critical component in areoengine. The evolution of δ phase has highly influence on the hot working process, microstructure evolution and performance. In this paper, GH4169 alloy which are solution treated and deformed at high temperature were conducted on aging treatment to investigate the morphology and precipitation mechanisms of δ phases. The volume fraction of δ phases increases with the Nb element content. The peak temperature for δ phases precipitation is 920℃ which is not influenced by the content of Nb element. The nucleation rate and volume fraction of δ phases increases with the decreasing of average grain size. Otherwise, the size of δ phases decreasing with 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 radius of vurvature. Otherwise, the nucleation rate of δ phases increases with the increasing of curvature. The distribution morphologies of δ phases precipitated at grain boundary are similar to needles, sawtoothes and fish tails.