Grain boundary precipitation in a nickel--beryllium alloy

The morphology and kinetics of discontinuous grain boundary precipitation have been studied in a nickel 1.89 wt. percent (11.1 at. percent) beryllium alloy. The cells were found to have an irregular lamellar structure with a continuous nickel rich phase and NiBe platelets. There is no consistent habit plane observed but at least three orientation relationships do exist between the two phases. The most frequently observed relation was [100]/sub NiBe/ parallel parallel [001]/sub Ni/ : (001)/sub NiBe/ parallel parallel (110)/sub Ni/. The kinetics of the reaction were found to follow a linear growth with time. The activation energy of approximately 55 kcal/mole is less than bulk self diffusion of nickel but greater than grain boundary self diffusion