Morphology transition of deformation-induced lenticular martensite in FeNiC alloys

One-step model of the face-centred-cubic to body-centred-cubic martensitic transformation

“…The many (110) // (111) planar defects observed in lenticular martensite by Jana & Wayman (1970), Shimizu & Nishiyama (1972), Sandvik & Wayman (1983) and in butterfly martensite by Umemoto et al (1984), Gong (1987) and Zhang et al (1993) might be explained as follows: the deformation of austenite in the surrounding of a nucleated martensite is accommodated by the disclinations A constituted by dislocations on a specific (111) Sandvik & Wayman (1983) could result from the accommodating disclinations w B (x4.2) and an inheritance mechanism during the martensitic transformation. The origin of serrations, which are small notches sometimes visible on the edge of martensite (Jana & Wayman, 1970;Maki et al, 1973) is still not well understood.…”

“…It is formed by two lenticular-shaped wings in two distinct {225} planes and, as a lenticular martensite, it can present the same internal features, such as a midrib, 'twins', (110) planar faults and serrations (Umemoto et al, 1984;Gong, 1987;Zhang et al, 1993). showed recently by EBSD that the lattice inside a wing is gradually deformed by a rotation around the common [111] = [110] axis with a maximum angle generally between 5 and 10 , i.e.…”

Martensitic Transformation under Stress in Ferrous Alloys. Mechanical Behaviour and Resulting Morphologies

“…Results indicate that i) for a given martensite content, the transformation plasticity deformation increases with the test temperature ii) for a given manensite content, the transformation plasticity depends on the deformation range (elastic or plastic deformation range of austenite, oy -200 MPa) iii) a more important transformation plasticity deformation is obtained when the transformation occurs at a higher value of o/X (i-e. at a same martensite content X the transformation plasticity is larger if the stress is larger, or at a same stress, the transformation plasticity is larger if the amount of martensite formed before is lower). TO understand the origins of these large deformations, microstructural observations of martensite formed during plastic deformation were performed for different Fe-Ni-C alloys [30,31,33]. From these studies it was shown that the martenste morphology changes when it is formed during deformation.…”

Transformation Mechanism of Deformation - Induced Compact Martensite in Fe-Ni-C Alloys

“…I t i m~l i e d that the austenitic nrain was locallv rotated and in the local region in Fe -30Ni -0. 34C alloy [3]. In the right variant of the lenticular couple -plate, some transfornation twinning bands seem to have extended into the austenite when the plate has further grown.…”

“…For the Fe -30Ni alloy, transitions in morphology were observed with progressive deformation levels going from lenticular to butterfly and to compact martensites. The deformation -induced butterfly martensites with different { I l l / r habit planes were conjugated closely to form the compact martensite in which the substructure was high densities of dislocations and no residual austenites were found between the conjunctive plates [3]. For the Fe -25Ni -0.…”