Relaxation of the Excess Free Volume of the Phase Transformation at the Interphase Boundary between the Crystal and the Melt

The mechanism of relaxation of the excess free volume of phase transformation released in the region of local dilation at the interphase boundary (MFG) of a crystal with a melt is considered. The analysis of the structural state of the MFG and its effect on the mobility of the boundary under the conditions of pressure application during the growth of the crystal from the melt is carried out. An explanation is given of the extreme influence of pressure on the mobility of the MFG and the possibility of the state of abnormally high mobility of the boundary under conditions of the application of “optimal” pressure in magnitude (“super-mobility” of the MFG). Within the framework of the mechanism of viscous melt flow into the region of local dilation at the MFG, which occurs during crystallization, a quantitative agreement was obtained with the experimental value of the “optimal” pressure in terms of magnitude, which determines the extreme nature of the mobility of the crystal boundary with the melt.