Effect of prior deformation on AS temperature of martensite in Fe-Ni alloys

Lath martensite of an Fe-15%Ni and lenticular martensite of an Fe-31%Ni alloy were prepared and the influence of prior deformation at room temperature on the start temperature of reverse transformation (As) in the martensites was investigated. The As and hardness of the lenticular martensite are raised simultaneously with increasing deformation, whereas those of the lath martensite, a greater driving force for the growth of austenitic nuclei in response to increased hardness is considered to shift the As to higher temperature. For the lath martensite, the constant hardness regardless of deformation degree is thought to be responsible for no change in As.