STABILIZATION OF AUSTENITE ASSOCIATED WITH PRIOR FORMATION OF MARTENSITE

The stabilization of retained austenite was studied via a two-step coo ling procedure. Alloys with M(s) temperatures below 0 degrees C were u sed. It was found that the martensitic transformation starting tempera ture, M(s), was lowered to M(s)' during the second step of cooling. Wi th increasing the amount of previously formed martensite, the differen ce in the transformation starting temperatures, Delta M(s) (= M(s) - M (s)'), increases. This stabilization effect can also be observed in an alloy having very low carbon content, and the magnetic properties of alloys do not have drastic effect on the nature of this stabilization phenomenon. The mechanism of the stabilization of retained austenite i s proposed to be mainly due to the inhibition effect produced by the p reviously formed martensite. The aging processes are considered to be a necessary condition for the above mechanism to operate.