gamma-prime Phase Stability and Phase Equilibrium in Ternary Co-W-Al at 900 °C
Eric Lass, Maureen E. Williams, Carelyn E. Campbell, Kil-Won Moon, Ursula R. Kattner
Phase equilibria at 900 °C in the Co-rich Co-W-Al ternary system is investigated through isothermal annealing of six alloy compositions for times up to 8000 h. The volume fraction of the L12-gamma-prime phase co-existing with disordered FCC-gamma, B2 and D019 phases is found to steadily decrease with increasing annealing time indicating that it is unstable at 900 °C. Additional heat treatments at 850 °C and 1000 °C further suggest it is a nonequilibrium phase at all temperatures in the ternary system. The L12-gamma-prime phase dissolves slowly with significant amounts remaining in some alloys after 8000 h at 900 °C. However, the present work clearly indicates the microstructure is moving toward a three-phase equilibrium between gamma, D019, and B2. The collected compositional and phase equilibria information provide much needed data for improving the available thermodynamic assessments of the ternary Co-W-Al alloy system.
, Williams, M.
, Campbell, C.
, Moon, K.
and Kattner, U.
gamma-prime Phase Stability and Phase Equilibrium in Ternary Co-W-Al at 900 °C, Journal of Phase Equilibria and Diffusion
(Accessed February 27, 2024)