Metastable Two-Phase Field(A2+B2) in Co-Al-Fe and Co-Al Alloy Systems
Precipitation of disordered bcc Co (A2) particles has been investigated in Co-rich B2 ordered Co-Al-Fe and Co-Al alloys by means of a macroscopic composition gradient method using a transmission electron microscope. When Co-Al-Fe ternary and Co-Al binary alloys were annealed at 823-1023K for a relatively short time, bcc disordered particles precipitated within B2 ordered matrix, followed by the formation of equilibrium fcc α-Co (A1) on the phase boundaries. The precipitation limit of metastable A2 phase was evaluated using the binary and ternary specimens with macroscopic compositional gradient. As a result, it was found that the limits are located within the equilibrium A1+B2 two-phase fields in both ternary and binary alloy systems, and that the limit curve on the isothermal section at 923K for Co-Al-Fe system successfully connects with the phase boundary of A2+B2 two-phase field at the Co-Fe binary side of the ternary system.
S.-G. Kang and T. Kobayashi
T. Kozakai et al., "Metastable Two-Phase Field(A2+B2) in Co-Al-Fe and Co-Al Alloy Systems", Materials Science Forum, Vols. 449-452, pp. 61-64, 2004