MEASUREMENT AND ANALYSIS OF GRAIN-BOUNDARY GROOVING BY VOLUME DIFFUSION

Experimental measurements of isothermal grain boundary grooving by volume diffusion are carried out for Sn bicrystals in the Sn-Pb system near the eutectic temperature. The dimensions of the groove increase with a temporal exponent of 1/3, and measurement of the associated rate constant allows the determination of the product of the liquid diffusion coefficient D and the capillarity length-GAMMA associated with the interfacial free energy of the crystal-melt interface. We generalize the small-slope theory of Mullins to the entire range of dihedral angles by using a boundary integral formulation of the associated free boundary problem, and obtain excellent agreement with experimental groove shapes. By using the diffusivity measured by Jordan and Hunt, we deduce that our measured values of GAMMA agree to within 5% with the values obtained from experiments by Gunduz and Hunt on grain boundary grooving in a temperature gradient.