INTERFACE CONFIGURATIONS DURING THE DIRECTIONAL GROWTH OF SALOL .2. THERMAL-STRESS CRACKING

A combined numerical and experimental work is carried out to determine the conditions for the onset of cracking during directional growth of macroscopically faceted crystals. The numerical simulation is based on a combined solidification, thermal and stress model. Results indicate that during growth, regions of the facet which initially experience high shear stresses and high compressive hydrostatic stresses may pass into regions of high tensile hydrostatic stresses. The cracking behavior is predicted from these results. For the screw dislocaton assisted growth, the cracking tendency is expected to depend only on the velocity of growth as the temperature gradient and spacing adjust to impose the same stresses for a fixed velocity of growth. For continuous growth and growth in the transitional regime, the stresses experienced by macroscopic facets is a function of (G/V)1/2, where G is the axial temperature gradient and V is velocity of the growth.