The Thermal Stabilization of Austenite in High-Nickel Steels

Abstract

The thermal stabilization of austenite has been studied in two high-nickel steels which transformed to martensite at sub-zero temperatures; the martensite was of {259}γ habit in one alloy and predominantly of {225}y in the other. In both steels appreciable stabilization was obtained after ageing between the ambient temperature and ⊂ 90°C. The observations are considered in the light of the previously proposed theories for stabilization. It is concluded that stabilization at well below O°C is due to stress-relaxation, although as the temperature of stabilization is raised the diffusion of carbon may become an increasingly important factor. The influence of habit plane of the martensite on stabilization supports the concept that the controlling mechanism acts to inhibit nucleation of the martensite.