Microstructures of rapidly solidified powder and extruded rod of Ni3Ge

Rapidly solidified powders and extruded rods of Ni3Ge with and without 0.06at.% boron were characterized using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The powders were generally spherical and exhibited both dendritic and lamellar structures. The increase in lattice parameter per atom fraction of boron, ε, was estimated to be 0.33. Extrusion of the powders produced fine grains of about 2μm in diameter. The extruded materials were partially recrystallized and showed a minor preference for {111} orientation. Annealing at 950 °C resulted in a fully recrystallized structure and a nearly random orientation. The addition of 0.06at.% boron had no observable effect on the morphology, microstructure, and texture. Precipitates of borides were observed in the annealed boron-doped alloy, suggesting that the solubility of boron in Ni3Ge may be below about 0.06at.%.