CRITICAL TEMPERATURE FOR GROWTH OF MARTENSITE

摘要

M_s may be defined as the temperature below which the formation of martensite starts upon cooling. It may also be useful to define M_g, the temperature below which martensite can grow if it is already nucleated. In order to analyze the mechanism of martensite formation, it is essential to know the difference M_g — M_s. We have tried to evaluate M_g — M_s for an Fe-C alloy with a decarburized surface zone in order to induce nucleation. The samples were studied by means of electron microprobe, serial sectioning and optical microscopy. The results indicate that M_g is surprisingly close to M_s. The possibility that M_s is controlled by growth rather than nucleation is discussed.