Abstract
It is shown that an adaptive transient phase can be formed along the martensitic transformation path to overcome thermodynamic and nucleation barriers caused by the transformation strain. A possible role of the adaptive phase in the thermal nucleation of the martensite is discussed. The structure of the adaptive phase is predicted from the strain accommodation condition. An example of the cubic→tetragonal transformation is considered. The crystal lattice parameters of the adaptive phase are expressed through those of the parent cubic phase and tetragonal normal martensite. It is shown that the 7R martensite in β′NiAl alloys is an example of the adaptive martensite.
