Orientation and Habit Plane Relationships for Carbide and Nitride Precipitates Molybdenum

Precipitation of group IVa carbides and nitrides (TiC, TiN, ZrC, ZrN, HfC, and HfN) in molybdenum has been studied with electron microscopy. The precipitates display a characteristic platelike morphology, and contrast effects suggesting coherent nucleation have been observed. The zirconium and hafnium carbides and nitrides exhibit a cubic {100} habit plane and an orientation relationship with the matrix characterized as follows:{100}Mo{100}ppt〈100〉Mo〈110〉ppt〈110〉Mo〈100〉ppt ike precipitates of titanium carbide and titanium nitride, however, exhibit an apparent {310}Mo habit plane. lysis of the mismatch parameters and an approximate calculation of the relative strain energies associated with coherency for various possible habit planes and matrix-precipitate orientation relationships confirm the {100}Mo habit for the zirconium and hafnium carbide and nitride precipitates. The theory predicts the observed {310}Mo habit plane for the titanium carbide and nitride phases with the following orientation relationship:{310}Mo{113}ppt〈113〉Mo〈112〉ppt〈100〉Mo〈110〉ppt