Some new experimental results on the Zr–Nb–Fe system

The scope of this study is the identification and characterization of intermetallic phases and their binary and ternary fields in the Zr–Nb–Fe phase diagram. A construction of the central region of the phase diagram at 900 °C was proposed using new experimental results obtained by optical and scanning electron microscopies, X-ray diffraction and microprobe analysis. In addition to the well-known Laves C15-type (ZrNb)Fe2 phase (the polytypic C14 and C36 structures were not detected in the studied compositions), another Laves C14-type phase was found (Zr(NbFe)2). Watson and Bennett maps helped to predict the occurrence of both of these phases. Moreover, the validity of the Pettifor prediction model for Laves phases in pseudobinary systems with transition elements was checked, verifying the obtained experimental results in the Zr–Nb–Fe system. On the other hand it was determined that the Zr–Nb–Fe ternary system at 900 °C, as it happens in the binary Zr–Nb system, would have a miscibility gap (β-Zr + β-Nb) in the 25–70 at.% Nb composition range, accepting up to 3 at.% Fe approximately.