Precipitation and dissolution behaviors of δ phase inside a deformed nickel-based superalloy during annealing treatment

The precipitation and dissolution behaviors of delta phase inside a deformed nickel-based superalloy during annealing treatment are investigated. A new method for quantitatively evaluating the content of delta phase was proposed based on SEM micrograph, which was verified by X-ray diffraction (XRD) analysis. The effects of recrystallization during pre-annealing at 980 degrees C on the precipitation and dissolution behaviors of delta phase in the subsequent annealing treatment at 900 degrees C and 980 degrees C are discussed. Moreover, the improved precipitation and dissolution kinetics models are proposed to consider the effects of recrystallization fraction. The results show that: (1) for the precipitation of delta phase at 900 degrees C, delta phases precipitate first in grain boundaries and then within grains after a long incubation period. Moreover, the interval between adjacent delta phases increases first and then drops with the increasing recrystallization fraction during pre-annealing treatment. A balance between the precipitation and solution of delta phase at the aging temperature of 900 degrees C can be reached when the holding time is about 12 h; (2) for the dissolution of delta phase at 980 degrees C, the dissolution equilibrium can be obtained at approximate 200 min. Moreover, more rod-like delta phases can be remained with the increasing recrystallization fraction in pre-annealing treatment.