Martensitic transformation defined

At Ms temperature TiNi initiates a uniform (inhomogeneous) distortion of its lattice — through a collective atomic shear movement. The lower the temperature, the greater the magnitude of shear movements. As a result, between Ms and Mr temperature the crystal structure is not definable. In sharp contrast, other known martensitic transformations initiate a nonuniform (heterogeneous) nucleation at Ms and thereafter the growth of martensite is achieved by shifting of a two dimensional plane known as invariant plane [28] at a time. Thus, between Ms and Mr temperature the crystal structure is that of austenite and/or martensite . 

Martensitic transformations are a general class of reactions that are similar to that found in steel. The main characteristic of this class of reactions is that they are very rapid, because no atom diffusion occurs. Martensitic transformations are defined by being diffiisionless reactions. 

Stress induced martensitic transformation is a transformation firom one ciystallographic form to another form and associated with a displacement of chains to new positions in the new crystallographic ceU in order to acconunodate the deformation. An example of martensitic transformation firom orthorhombic to monoclinic form was found in oriented polyethylene with well defined texture subjected to uniaxial compression. Martensitic transformation was also found in other polymers in poly(L-lactic acid) [119] and in nylon 6 with the a-form transforming to the 7-form [120,121]. 

Outside of the well-defined limits mentioned above, anomalous behaviors were observed in the cold-worked 301 stainless steels which were found to have been caused by a solid-state transformation of austenite (face-centered cubic) to martensite (body-centered tetragonal). This austenite to martensite reaction, which had a strong influence on all of the properties studied, is known to be favored by both low temperature and high strain [2]. In this study, martensite was... 

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