ELECTRON-MICROSCOPY STUDY OF NI NI3AL DIFFUSION-COUPLE INTERFACE .1. MICROSTRUCTURAL OBSERVATION AND MICROCHEMICAL ANALYSIS/

The Ni/Ni3Al diffusion-couple interface has been examined using the te chniques of analytical electron microscopy and high-resolution electro n microscopy. It is shown that the Ni-rich solid solution phase (gamma phase) is transformed from the Ni3Al-based intermetallic phase (gamma ' phase) and that it extends into the gamma' phase during diffusion an nealing. The orientations of the gamma and gamma' phases remain the sa me. Coherency exists across the gamma/gamma' phase boundary. The posit ion of the boundary is not well defined but it is in an equilibrium co ndition in terms of composition.