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June 26, 2023
Conference Paper
Title
Experimentally screening the oxidation resistance and microstructure of refractory metals-based high-entropy alloys (RHEAs) with varying compositions
Abstract
High-Entropy Alloys (HEAs) based on refractory metals alloyed with light metals (RHEAs) show a promising combination of low density and high compression strength at high temperatures. Thus, the high potential of these alloy systems for high-temperature applications beyond nickel-based superalloys has risen extensive research interest.
In this work, AlMo0.5NbTa0.5TiZr, AlCrMoNbTi and AlCrMoTaTi were chosen as base RHEAs for variations in chemical compositions and experimental screening of isothermal oxidation resistance. In order to improve the three base alloys in terms of oxidation resistance and density, fractions of Al, Ti and Cr/Zr are systematically modified, respectively. Furthermore, the influence of Si additions is investigated. Thus, a total of 55 RHEAs 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 RHEAs is screened gravimetrically by weighing before and after isothermal oxidation testing for 48 h at 1000°C in air. Selected promising RHEAs with highest oxidation resistances are investigated in more detail regarding phase composition, microstructure, mechanical properties and oxidation behaviour.
RHEAs are characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), Vickers hardness testing and compression testing. Experimental findings are supplemented by thermodynamic data using CALPHAD simulations.
In this work, AlMo0.5NbTa0.5TiZr, AlCrMoNbTi and AlCrMoTaTi were chosen as base RHEAs for variations in chemical compositions and experimental screening of isothermal oxidation resistance. In order to improve the three base alloys in terms of oxidation resistance and density, fractions of Al, Ti and Cr/Zr are systematically modified, respectively. Furthermore, the influence of Si additions is investigated. Thus, a total of 55 RHEAs 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 RHEAs is screened gravimetrically by weighing before and after isothermal oxidation testing for 48 h at 1000°C in air. Selected promising RHEAs with highest oxidation resistances are investigated in more detail regarding phase composition, microstructure, mechanical properties and oxidation behaviour.
RHEAs are characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), Vickers hardness testing and compression testing. Experimental findings are supplemented by thermodynamic data using CALPHAD simulations.