Some remarks on the nucleation and growth of martensite

It is generally agreed that the difficult step in the formation of isothermal as well as athermal martensite is the nucleation since the growth occurs at a high speed. Previously the difference between Ms and Mg, the temperature below which martensite can grow if it is already nucleated, was determined for an Fe-1.62%C alloy. The difference was surprisingly small indicating that the difference in driving force for nucleation and growth is small. This experimental result is here compared with results on both athermal and isothermal martensite. A discussion about the critical step for the formation of lath and plate martensite formed by rapid continuous cooling is also given.