材料期刊网

The morphology and habit planes of deformation-induced lenticular martensite were investigated by optical and transmission electron microscopy in Fe-30Ni and Fe-30Ni-0.11C alloys. Transitions in morphology were observed with progressive deformation levels going from lenticular to butterfly and to compact martensite for the Fe-30Ni alloy and lenticular to butterfly and to small butterfly martensite for the Fe-30Ni-0.11C alloy. The habit planes changed from {225}f or {259}f for the thermal lenticular martensite to {111}f for the strain-induced martensite. The morphology and crystallography of the small butterfly martensites was also investigated. A change in the orientation relationships from K-S to N-W relations was also observed. These changes were attributed to the contribution of mobile dislocations which modified the shear mode from twinning to slip, and to a plastic accommodation of transformation strains.