Abstract
Knowledge on phase stability in Fe-rich Fe-Cr-Ni-Zr alloys is needed for the development of Laves-phase strengthened Fe-Cr-Ni-Zr ferritic alloys which have shown promising applications as new cladding materials of nuclear reactors due to enhanced high temperature strength, and resistance to creep and irradiation hardening. Phase stability in four Fe-rich Fe-Cr-Ni-Zr alloys was carefully investigated using scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. The samples were arc-melted and heat treated at 700 ∘C for 336 hours and 1000 ∘C for 1275 hours. The experimental results showed extensive solubility of Ni in the intermetallic phases Fe23Zr6 and Fe2Zr_C15. Nickel stabilizes the Laves Fe2Zr_C15 structure more than the C36 and C14 structures. In addition to Fe23Zr6 and Fe2Zr_C15, Ni7Zr2 was found to be stable in samples with higher Ni content and lower annealing temperature. The body-centered-cubic, Fe2Zr_C15 and Fe23Z6 coexist in all samples regardless of composition and temperature. Detailed analysis suggested that the coexistence of these three phases is not a result of thermodynamic equilibrium, but a result of the competing formation kinetics of Fe2Zr_C15 and Fe23Z6.
