Refractory multi-principal element alloys are promising candidates for high temperature structural applications offering lower density and mechanical properties comparable to advanced Ni-based superalloys. One limitation of these alloys remains their moderate high temperature corrosion resistance due to the formation of unfavourable oxides. One example of such a refractory multi-principal element alloy, Ta-Mo-Cr-Ti-Al, was recently investigated by Müller at al.  and showed some promising oxidation resistance.
In this work, a modification of the aforementioned alloy namely Ta-Mo-Ti-Al is investigated. Chromium is deliberately removed from the alloy composition to supress the formation of Cr rich Laves phases. Ta-Mo-Ti-Al alloys with varying compositions were obtained via direct laser deposition (DLD) using the Trumpf Laser Cell 7040 and four hoppers. The effect of DLD processing parameters on the formation of the microstructure is reported. Their microstructure and phases were analysed using scanning electron microscopy (SEM) and XRD analysis. Several heat treatments are performed to analyse the thermal stability of the alloy in the range of 1000-1200°C and mechanical tests are performed to assess the performance of the alloys.
 F. Müller, B. Gorr, H.-J. Christ, H. Chen, A. Kauffmann, M. Heilmaier, Effect of microalloying with silicon on high temperature oxidation resistance of novel refractory high-entropy alloy Ta-Mo-Cr-Ti-Al, Materials at High Temperatures 35(1-3) (2018) 168-176.