Dissolution kinetics and behavior of δ phase in Inconel 718
摘要
Dissolution kinetics of δ phase in Inconel 718 at 980,1000 and 1020℃ respectively was established using the quantitative X-ray diffraction(XRD)method.Microstructure evolution during dissolution process was analyzed with scanning electron microscopy(SEM).Dissolution rate of δ phase during high temperature heating keeps at a high level at the beginning stage,and then decreases gradually with the increase of heating time.A dynamic equilibrium state approaches after being heated at 980℃ for more than 30 min and at 1000℃ for more than 2 h,and the equilibrium mass fraction are 3% and 0.6% respectively.δ phase fully dissolves into the austenitic matrix after being heated at 1020℃ for more than 2 h.The dissolution and fracture effects cause the morphology evolution of δphase from long needle shape to short bars or particles at high temperature.