Physical and Theoretical Chemistry

Biography

Biography: Osman Adiguzel

Abstract

Some materials take place in class of smart materials with adaptive properties and stimulus response to the external changes. Shape memory alloys take place in this group with shape reversibility character and capacity of responding to changes in the environment. These alloys exhibit a peculiar property called shape memory effect, which is characterized by the recoverability of two certain shapes of material at different temperatures. This property is characterized by the recoverability of two certain shapes of material at different temperatures. These alloys possess two unique abilities: the capacity to recover large strains and to generate internal forces during their activation. Shape memory effect is initiated by successive cooling and deformation treatments, and activated thermally on heating and cooling, with which shape of material cycles between original and deformed shapes in reversible way. Therefore, this behavior can be called Thermoelasticity. The basis of this phenomenon is the stimulus-induced phase transformations, thermal and stress induced martensitic transformations, which govern the remarkable changes in internal crystalline structure and properties of the materials. Thermal induced martensitic transformation occurs on cooling, with cooperative movement of atoms in, <110> type directions on the {110} type planes of austenite matrix, along with lattice twinning and ordered parent phase structures turn into twinned martensite structures. The twinned structures turn into detwinned structures by means of stress induced transformation by stressing the material in the martensitic condition. Martensitic transformations are diffusion less transformations, and movements of atoms are confined into neighbor atom distances.