Phase stability and defect structures were studied in a C15 Laves phase by performing a combined experimental and theoretical investigation. It was found that C15 V2Hf could be alloyed with some 20at%Nb, where the Nb atoms occupied both Hf and V sites. The lattice parameters of ternary C15 phases with the same Nb content decreased with increasing V/Hf ratio. The extended defects which were observed in the ternary C15 phase were extrinsic {111} stacking faults, {111}<112> annealing twins, and faceted Σ = 3 <111> 70.53º grain boundaries. An examination of the extrinsic {111} stacking faults revealed that synchro-shear could occur in this phase.

Phase Stability and Defect Structure of the C15 Phase in the Hf-V-Nb System F.Chu, Y.C.Lu, P.G.Kotula, T.E.Mitchell, D.J.Thoma: Philosophical Magazine A, 1998, 77[4], 941-56