Identification of stress-induced nucleation sites for martensite in Fe-31.8 wt% Ni-0.02 wt% C alloy

Abstract

A novel plate impact recovery technique has been used to study the incubation time, the inception, and the initiation and growth of martensitic transformations in an Fe-31% Ni-0.02% C alloy, at a temperature of M s + 10°C. The technique allows subjecting the sample to a single tensile pulse of pre-assigned duration and amplitude. The amplitude of the tensile pulse sufficient to induce transformation at the test temperature, was about 1.5 GPa. For a tensile pulse duration of 80 ns, martensitic transformation was observed to have been initiated, but no fully transformed martensite lensen were produced. For a tensile pulse of 105 ns duration, in addition to small incompletely grown lenses, fully grown martensite lenses were observed. The majority of these martensite lenses abutted the annealing twin boundaries, suggesting that these boundaries are favored nucleation sites for tensile stress wave-induced martensite in the system under investigation.