Correlations to improve high-temperature strength and room temperature ductility of refractory complex concentrated alloys

Correlations were explored between mechanical, thermodynamic and physical properties of refractory complex concentrated alloys (RCCAs). Experimentally measured yield strengths (σy) and ductility were taken from the open literature and were compared against liquidus, solidus and solvus temperatures, elastic properties (Young's, shear and bulk moduli), density (ρ), surface energy (γ) and valence electron concentration (VEC). If not publicly available, the thermodynamic properties were calculated using CALPHAD while the other properties listed above were estimated using a rule-of-mixtures average of the constituent element properties. This analysis emphasized tensile ductility. Based on the identified correlations, useful criteria for selecting possibly ductile RCCA compositions with good high-temperature strength were proposed, a few ductile and strong RCCAs were made and properties of some of them were reported in this paper. Additionally, multivariate linear regression (MLR) was used to identify new insights from the high dimensional space of the present study by modeling the influence of composition and the input thermodynamic and physical properties on the high-temperature strength and room temperature ductility. Equal concentrations of Mo and Nb in RCCAs were found to give a good balance of strength and ductility. The MLR analysis identified over 50 promising RCCAs for intended high-temperature applications, pending experimental confirmation.