Papers by Keyword: Martensite Stabilization

Abstract: Shape memory alloys exhibit a peculiar property, shape memory effect that is the result from the structural changes in microscopic scale. These alloys return to previously defined shapes when they are subjected to variation of temperature after deformation of the low temperature phase. Shape-memory effect is based on martensitic transformation, with which the material changes its internal crystalline structure. The ordered structure or super lattice structure is essential for the shape memory effect of the material. Copper based alloys exhibit this property in the β-phase field, which possesses the simple bcc-structure at high temperature austenite phase. As the temperature is lowered, austenite phase undergoes martensitic transition following two ordering reactions, and microstructural changes in microscopic scale govern this transition. In the present work, Cu alloys were investigated by transmission electron microscope, TEM, and x-ray diffraction techniques.

Abstract: The Landau theory has been developed for the description of martensite aging. The characteristic features of the theory are: i) the multicomponent non-scalar character of the order parameter describing the slow reconfiguration of lattice defects after martensitic transformation (MT); ii) the complete agreement with Symmetry-Conforming Short-Range-Order principle formulated by X. Ren and K. Otsuka; iii) the applicability to the different MT-s and various defects related to aging phenomena. The physical values interpreted as the components of internal stress, which stabilizes certain variant of martensitic phase, have been composed of the components of slow non-scalar order parameter. An applicability of the developed theory to the description of influence of aging on the MT temperature and yield stress was demonstrated.