AlMo0.5NbTa0.5TiZr was the first published refractory complex concentrated alloy (RCCA) [1] with inverted superalloy-like microstructure, showing a high volume fraction of cuboidal particles in a matrix phase analogue to nickel-based superalloys [2]. Hence, the term RCCA superalloy was created [3]. The reported combination of low density and high compression strength at 1000 °C shows the high potential of this alloy system for high-temperature applications.
In this work, AlMo0.5NbTa0.5TiZr and chemical derivatives are synthesised and screened in terms of oxidation testing. Selected RCCAs with highest oxidation resistances are tested thermogravimetrically to investigate oxidation kinetics.
In order to improve AlMo0.5NbTa0.5TiZr in terms of oxidation resistance and density, fractions of Al, Ti and Zr are systematically modified, respectively. Furthermore, the influence of Si additions is investigated. Thus, a total of 17 RCCAs are synthesised by vacuum arc melting, milling, spark plasma sintering (SPS), homogenisation heat treatment and surface preparation. Densities are determined by Archimedes method. The oxidation resistance of all RCCAs is screened gravimetrically by weighing before and after oxidation testing for 48 h at 1000 °C in air. Specimens are characterised both in homogenised and oxidised condition using metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experimental findings are compared to thermodynamical data using CALPHAD simulations.