Papers by Author: Q.P. Meng

Abstract: The free energy function of martensitic transformation is established using Landau polynomial. According to the free energy function, the interfacial structural modification of austenite-martensite with the chemical driving force of martensitic transformation and elastic constants of materials is discussed. Some characteristics of martensitic transformation, such as the difference between thermoelastic and nonthermoelastic martensitic transformation, martensitic growth, are explained.

Abstract: Previous works on the kinetics of martensitic transformation in shape memory materials through Landau theory and the application of the phase field theory to study phase transformations in alloys are briefly reviewed. Based on field model to improper martensitic transformation proposed by Wang and Khachaturyan in 1997, a simpler model is suggested. Using this model, the motion speed and shape of parent/martensite and martensite-martensite interface are quantitatively described, which are important factors to be considered in design of smart device using shape memory materials as a main element.

Abstract: The quantitative relationships are suggested that the applied stress decreases the nucleation barrier and activation energy of nucleation of martensitic transformation, and strain increases the nucleus sites. Taking Fe-20Ni-0.5C and Fe-25Ni-0.66C alloys as examples, their different martensitic morphologies in thermal-mechanical processing can be explained and the origin of such a difference may be revealed based on the above theoretical analysis. Accordingly, the control of martensitic morphologies in thermal-mechanical processing of ferrous alloys will become possible.