Experimental investigation of phase equilibrium in the Al–Nb–Hf ternary system at 600 °C and 400 °C

The phase equilibria in the Al–Nb–Hf ternary system at 600 °C and 400 °C were experimentally investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe microanalysis (EPMA/WDS). In each isothermal sections, 13 three-phase regions were measured. And their phase region boundaries were precisely determined. Among the actually measured binary compounds, only Al3Nb, AlNb2 and AlNb3 have a large range of solid solubility. In addition, two stable ternary compounds τ1-Al11Nb4Hf5 and τ2-Al2NbHf2, which had certain solid solubility, were newly discovered. On the basis of the experimental results and reasonable inference, the isothermal sections of ternary system at 600 °C and 400 °C were constructed.