ON ROTATING SPHERE-ON-A-PLATE EXPERIMENTS AND THE QUESTION OF WHETHER HIGH ANGLE GRAIN-BOUNDARIES MELT BELOW BULK MELTING TEMPERATURES

The question of whether high angle grain boundaries in metals undergo complete melting at temperatures significantly below bulk melting temperatures, T//M, has been longstanding. In this study, the authors conclude that essentially all the boundaries in the rotating copper and silver sphere-on-a-plate experiments at 0. 96 T//M and 0. 99 T//M could not have been completely melted. Instead, it appears that they remained crystalline and that the rotation occurred because of the dependence of their energy on crystal misorientation. Possible situations include a variety of cases where the boundary is considerably disordered but where the atomic positions are still highly correlated with the atomic positions in the two grains adjoining the boundary slab.