Reversed Austenite Growth Behavior of a 13%Cr-5%Ni Stainless Steel during Intercritical Annealing

Abstract

The austenite growth behavior during intercritical annealing of a martensitic stainless steel 13Cr-5Ni was investigated using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and Thermocalc-Dictra simulation. The samples were firstly heated to 650°C with the heating rate of 10°C/s, and then cooled to room temperature without holding for anytime. Experimental results show that reversed austenite tends to nucleate and grow with an acicular shape along lath boundaries (LAMSBs) and with a globular shape along grain boundaries (GBs). Alloy samples were then held at 650°C for different times, and both the EBSD and XRD results show that the amount of retained austenite at room temperature firstly increases with holding time, displaying a peak at about 20 minutes, and then starts to decrease. Together with the Thermocalc-Dictra simulation results and our previous results, this observation indicates that the austenite growth is accompanied with the diffusion of Ni from matrix to reversed austenite.