Stability of reversed austenite in 9Ni steel

The samples of 9Ni steel were treated by Quenching + Tempering (QT) and Quenching + larmellarizing + Tempering (QLT). The morphology, thermal stability and mechanical stability of the reversed austenite in 9Ni steel were studied by TEM, XRD, EBSD, subzero treatment, three-point bending, uniaxial tension and uniaxial compression. It turns out that blocky reversed austenite occurs in QT-treated steel, while blocky and filmy reversed austenite occurs in QLT-treated steel, additionally, the filmy reversed austenite distributes in the lath boundaries. Subzero treatment shows that certain amount of reversed austenite in QLT-treated samples transforms after dipping into liquefied nitrogen, but it retains a higher level of more stable austenite in QLT-treated sample than that in QT-treated sample. Both tension and compression facilitate the transformation of reversed austenite into martensite, and the retained austenite mainly locates within grains.