2015 Volume 55 Issue 1 Pages 293-299
This paper reports the precipitation kinetics along the eutectoid-type reaction path of δ-Fe → γ-Fe+Fe2Hf in an Fe-9Cr-0.3Hf (wt.%) alloy. Three types of precipitation modes were observed in the reaction path: (1) interphase precipitation forming periodically arrayed rows of fine Fe2Hf particles, (2) the precipitation of Fe2Hf phase in the δ phase followed by a phase transformation from the δ phase to the γ phase and (3) the precipitation of Fe2Hf phase in the γ phase matrix preceded by a δ → γ phase transformation. The nose for the interphase precipitation in time-temperature- transformation diagram is located at a few second and at 1100°C. The interphase precipitation is expected to be used as a tool for strengthening heat resistant ferritic steels, but the heat treatment window for the precipitation mode is narrow in the ternary alloy.
