A metastable b.c.c. phase and its decomposition behavior in rapidly solidified Ni-10at.%Zr and Ni-8at.%Zr-1at.%X alloys

A metastable b.c.c. (A2) phase with lattice parameter a = (0.280 ± 0.005) nm is obtained upon rapidly solidifying Ni-10at.%Zr and Ni-8at.%Zr-1at.%X (X = Si, Ti, Mo) alloys. The b.c.c. phase is relatively more stable in the ternary alloys. Formation of this metastable phase and the equilibrium phases under rapid solidification conditions are discussed in terms of classical nucleation theory. Upon aging, the b.c.c. phase decomposes into equilibrium phases, the morphology of which is dependent on the aging temperature.