Atomic structure of interfaces between Mn3O4 precipitates and Ag studied with HRTEM

Internal oxidation of Ag-3 at.% Mn resulted in Mn3O4 precipitates with a ''parallel'' topotaxy with the metal matrix and an octahedron shape due to {111} facets. Orientation and shape of Mn3O4 in Ag are not in the lowest strain energy state, indicating the dominance of interfacial energy over strain energy. Owing to the tetragonality of Mn3O4, only a few planes and directions of Ag and Mn3O4 can be parallel simultaneously. The precipitates exhibited a tendency to align {111} planes with the matrix one pair of facets and then for another pair a tilt of 7.6 degrees occurs which is relieved by ledges in Ag. The dislocation structure at these parallel and tilted {111} interfaces. including phenomena such as stand-off and dissociation of (partial) dislocations, is scrutinized combining HRTEM and atomistic calculations. (C) 1997 Acta Metallurgica Inc