Phase constituents near the center of the Co–Cr–Fe–Ni–Ti system at 1000 °C

Abstract

Abstract The phase constituents of Co–Cr–Fe–Ni–Ti alloys at 1000 °C, with Cr and Fe each fixed at 20 at.%, were investigated using X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. A series of alloys were prepared via the arc-melting method and annealed at 1000 °C for 30 d. None of the alloys were in the single-phase region. The σ- and χ-(Cr13Fe35Ni3Ti7) phases were confirmed to exist in the center of the system. The alloys with more than 15 at.% Ti were composed of two or more intermetallic phases, and no fcc solid solution was present. Eight phase regions were found near the center of the Co–Cr–Fe–Ni–Ti system, i.e., fcc + D024, fcc + D024 + σ, σ + D024 + C14, fcc + D024 + σ + χ(Cr13Fe35Ni3Ti7), D024 + σ + χ + C14, bcc + D024 + C14, D024 + C14 + bcc + B2 and fcc + C15 + fcc#2. All detected phases contained 5 elements and had their own unique compositions. Moreover, comparing the experimental results with thermodynamic calculations based on the PANHEA database showed that the present database cannot satisfactorily predict the phase constituents in the center of the Co–Cr–Fe–Ni–Ti system. The result presented will be helpful in phase composition analysis and in composition design of related systems.