Atomic ordering and structural transformation in the V-Co-Ni ternary alloys

The transformation behavior of the close-packed ordered nine-layered hexagonal structure (κ phase) existing in the V-Co-Ni ternary alloys was investigated by various metallurgical methods. Both neutron and X-ray diffraction indicate that atomic ordering and structural transformation take place separately. The isothermal aging at subcritical temperatures resulted first in the formation of cubic long-range-ordered α' from the fcc α matrix and subsequently transformation of the α' to hexagonal κ. The α' to κ transformation proceeds by nucleation and growth; however, both mode and morphology of transition vary with reaction temperature. These observation have been discussed in terms of the temperature dependence of nucleation and growth processes. The structural transformation produces massive substructures, which harden the alloy substantially. © 1973 The Metallurical Society of American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., and American Society for Metals.