Experimental determination of the isothermal sections and liquidus surface projection of the Mo–Si–V ternary system

Abstract

Abstract The phase equilibria of the Mo–Si–V ternary system were experimentally determined, including the isothermal sections at 1200 and 1450 °C, as well as the liquidus surface projection. The microstructures, crystal structures and phase constitutions of the as-cast and the annealed alloys in whole composition range were investigated by means of scanning electron microscopy equipped with energy dispersive spectroscopy, electron probe microanalyzer and X-ray diffraction. Five three-phase regions and ten two-phase regions were confirmed and no ternary compounds were observed in isothermal sections at 1200 and 1450 °C. In addition, the solidification paths of different Mo–Si–V alloys were analyzed to verify the primarily solidified phases. The stoichiometric compounds Mo5Si3 and V5Si3 have the same structure-type (W5Si3), however, they have two different compositions in the Mo–Si–V ternary system. They form two-line compounds Mo-rich Mo(V)5Si3 and V-rich V(Mo)5Si3. Eight primary solidification regions were finally confirmed on the basis of the study on the solidification processes of the as-cast alloys. The present experimental results are useful for the thermodynamic assessment of the Mo–Si–V ternary system, and the database development for the multi-component Nb/Mo–Si-based superalloy system.