Explanation

It is a kind of displacement type diffusionless transformation. The phase transformation is carried out in the form of lattice shear, and the total shear of phase transformation can be divided into two parts. One is the shear parallel to the habitual surface (causing the shape change of the phase transformation zone), the other is the expansion perpendicular to the habitual surface (causing the volume change). The displacement property of phase transformation produces a surface bulge. The reference line of the surface twists in the phase transformation area but remains continuous on the interface. During phase transformation, there is a shear in the martensite that keeps the lattice unchanged: slip or twinning.

Classification