Transformation of grain boundary structure inferred from the changes in the dihedral angle distribution in NiMn2

NiMn2 polycrystals, prestrained 4%, were annealed at temperatures of 0.6-0.9 T sub m and measurements were made of the grain sizes and dihedral angles at grain boundary triple junctions. Although the shape distribution of grain sizes remains almost constant, the distributions of dihedral angles show significant changes. After annealing at 0.7 and 0.8 T sub m , the standard deviations of dihedral angles is much higher than after annealing at 0.6 and 0.9 T sub m . The results are explained using the concept of grain boundary transformation. 9 ref.--D.O.N.