Abstract
(Co1?xNix)79.3B20.7 (x = 0, 0.25, 0.5, 0.75, 1) alloys were solidified at different undercoolings, aimed at the effect of Co/Ni atomic ratio on the metastable phase formation and stability. Substitution of Co by Ni reduces the possibility for metastable M2B (M = Co or/and Ni) phase to form as primary solid at medium undercoolings. As a result, M2B phase completely disappears from the solidification of the alloys with x = 0.5, 0.75 and 1. All the Co-Ni-B alloys investigated solidify into single metastable M23B6 phase at large undercooling. The stability of metastable M23B6 phase however becomes worse as the Ni content increases, due to which it is decomposed into α-M and M3B phases in the post-solidification cooling process when x ≥ 0.75. A vertical section of the Co-Ni-B phase diagram with a content of 20.7 at% B was drawn, including the liquidus temperatures of M3B, M2B and M23B6 phases and the eutectic temperatures of L → α-M + M3B and L → α-M + M2B.
NSTL
Elsevier