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 diffr action. The powders were generally spherical and exhibited both dendri tic and lamellar structures. The increase in lattice parameter per ato m fraction of boron, epsilon, was estimated to be 0.33. Extrusion of t he powders produced fine grains of about 2 mu m in diameter. The extru ded materials were partially recrystallized and showed a minor prefere nce for {111} orientation. Annealing at 950 degrees C resulted in a fu lly recrystallized structure and a nearly random orientation. The addi tion of 0.06at.% boron had no observable effect on the morphology, mic rostructure, and texture. Precipitates of borides were observed in the annealed boron-doped alloy, suggesting that the solubility of boron i n (NiGe)-Ge-3 may be below about 0.06at.%. (C) Elsevier Science Inc., 1996