EBSD Microstructure Characterization of 9% Nickel Steel during In Situ Heat Treatment

The austenite content in 9% Ni steel was investigated with EBSD during and after in situ heating to different temperatures in the two phase region of the phase diagram, after first obtaining a coarse grained HAZ using weld simulation. This temperature region was discovered to be much narrower than during equilibrium. The austenite formed at 590°C grew slowly and was stable after cooling to ambient temperatures. The austenite grew at laths and previous grain boundaries. The fraction retained austenite varied from 5 to 25% depending on the area investigated. The austenite formed at higher temperatures was not stable, and the retained austenite content varied from 1 to, in the temperatures closeset to 590°C, 5%. The quality of the austenite phase was confirmed by using Kurdujmov-Sachs orientation relationship