Abstract
Phase equilibria in the Al-Cr-V system have an important role for designing of low-density Al containing refractory multiprincipal element alloys. In order to improve the literature data related to this system and contribute with the development of alloys with good oxidation resistance, the liquidus projection of the Al-Cr-V system is proposed for the first time in the present work. The experimental investigations were carried out via microstructural characterization of twenty-four as-cast alloys using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). Results showed no signs of ternary compounds and the limits of the primary precipitation fields are proposed. The primary precipitation field of BCC is preponderant in relation to those of the other phases. Me5Al8 aluminide with D82 crystal structure is present in both Al-Cr and Al-V systems (namely V5Al8 and the high temperature β-Cr5Al8) with a complete mutual solution of V and Cr forming a primary precipitation field connecting both diagrams (Al-V and Al-Cr). The VAl3 and CrAl4 primary precipitation fields were also determined. Three class II ternary invariant reactions are suggested based on experimental data: (UI) Liquid + α-Cr5Al8 ? Me5Al8 + CrAl4; (UII) Liquid + Me5Al8 ? VAl3 + CrAl4 and (UIII) Liquid + CrAl4 ? VAl3 + Cr2Al11. Four other class II and one class I ternary invariant reactions are suggested based on thermodynamic extrapolated data: (UIV) Liquid + Cr2Al11 ? VAl3 + CrAl7; (UV) Liquid + VAl3 ? V4Al23 + CrAl7; (UVI) Liquid + V4Al23 ? CrAl7 + V5Al47; (UVII) Liquid + V5Al47 ? CrAl7 + V2Al21 and (PI) V2Al21 + CrAl7 + Liquid ? (Al)-FCC.
NSTL
Elsevier