Abstract

    Certain solids can exist in more than one phase, each phase being characterized by it's own distinct crystal structure. A stress-induced phase transformation in a single crystal of such a material occurs by the propagation of one or more sharp interfaces - phase boundaries -- through the specimen.  When a material particle crosses such a moving interface it transforms from one phase to another, this being a transition from a metastable state to a more stable state. The response of such a material is typically hysteretic. For some materials this hysteresis is quite large, for others it is negligible. According to continuum thermodynamics, the speed of propagation of an interface depends on the associated driving force, but it does not specify the form of this relation. Therefore, the continuum theory, on its own, cannot, for example, explain the difference in the size of the hysteresis, or the related fact that some phase boundaries are very easy to move while others are extremely resistant to motion. In this talk we will review the continuum theory of mobility, and then describe two mechanisms: one involves the motion of a ledge along the interface, and the other involves the splitting of the tips of martensitic bands.

Biobibliography

    Dr. Abeyaratne graduated from University of Ceylon in 1975, and he got his MS degree and Ph.D degree in Applied Mechanics from California Institute of Technology in 1976 and 1979, respectively. He is now the head of Department of Mechanical Engineering of Massachusetts Institute of Technology (MIT) and Quentin Berg Professor of Mechanical Engineering of MIT. Dr. Abeyaratne received many honors including President-elect, American Academy of Mechanics, MacVicar Faculty Fellow of MIT, Fellow of ASME, Fellow of American Academy of Mechanics, and Den Hartog Distinguished Educator Award, etc.