The Co-Ni-Si (Cobalt-Nickel-Silicon) System

The Co-Ni system is a simple isomorphous system with liquidus and solidus temperatures very close to each other. The Co-Ni-Si system was investigated using arc melted alloys as well as using diffusion couples. Binary and ternary alloys were arc melted under argon atmosphere. The alloys, sealed in evacuated quartz capsules, were annealed and quenched in water. The diffusion couples prepared with Si and Co and three Co-Ni alloys of compositions were annealed in a vacuum furnace at 800°C. The annealed binary and ternary alloys and the diffusion zones of the diffusion couples were investigated using polarized light microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques. The Co-Ni-Si ternary system at 800°C shows continuous solid solution regions δ and ζ between the Co 2Si and Ni 2Si phases and between the CoSi 2 and NiSi 2 phases.