A micromechanics based model for martensitic phase transformations

Martensitic phase transformations are solid to solid phase transformations,which have an important role in determination of mechanical properties ofsteels and represent the main deformation mechanism of shape memory alloys.During such transformations, large transformation strain in some regions ofa body results in development of large stresses. At these regions, inelasticstrains develop and a ects the thermodynamics and kinetics of the phasetransformation. Determination of changes that occur in the microstructureduring phase transformation taking place under applied load and temperatureenables the design of mechanical properties of a material with respect to thesechanges. For this purpose, micromechanics based models for martensitic phasetransformations in elastic and inelastic materials (Ozsoy and Levitas, 2007) havebeen developed recently. Although a detailed numerical study has been made forelastic materials in the study, real material parameters have not been used. Also,numerical study of martensitic phase transformations in inelastic materials hasnot been completed.In this thesis study, rstly, the model developed by Ozsoy and Levitas (2007) forelastic materials is studied numerically for a shape memory alloy and veri ed bycomparison with experimental results. Then, the model developed for inelasticmaterials is studied numerically by developing a computational technique todetermine the changes in microstructure under di erent conditions, the reasonbehind such changes, and in uence of plastic deformation and applied stress ortemperature on phase transformations.Keywords: Martensitic Phase Transformations, Micromechanics, Plasticity.