Abstract
A number of non-equimolar refractory high entropy alloys (RF HEAs) from the Al–Ti–Mo–Nb–V system are synthesized, with the selected compositions aimed to balance the conflicting requirements of the low-temperature ductility and high-temperature corrosion protection. Based on the thermodynamic modeling and experimental results, all the obtained alloys are characterized by the single-phase B2 structure with V acting as the main phase stabilizer. The microstructure and mechanical properties appear to be controlled mainly by the Al content, which is especially visible on the example of hardness, with a maximum value of 545 HV for Al20Ti5Mo25Nb25V25 composition. For the selected Al20Ti5Mo25Nb25V25 and Al10Ti30Mo20Nb20V20 alloys, the measured stress–strain curves indicate the highly coveted, ductile room temperature behavior, with the values of ultimate strain measured under compression mode being 9.17 and 9.00 pct, respectively, and compressive fracture strain of 13.38 and 13.25 pct, respectively. The obtained results suggest that it is possible to include Al as a vital component of refractory HEAs without compromising their low-temperature ductility. The next intended step will be the characterization of the high-temperature corrosion behavior in order to investigate the potential selective oxidation capabilities of such materials.
Highlights
THE high entropy alloys—HEA’s are currently one of the most intensively explored directions of studies in materials engineering
Considering the as-cast state of the alloys presented in this study, based on the results of thermodynamic modeling, it can be expected that the alloys should exhibit a single-phase structure, with the ordered body-centered cubic B2 phase being present in all cases
The thermodynamic modeling indicates the presence of a single-phase, B2 structure in all considered as-cast alloys, with the Mo25Nb25V25-based series being characterized by the tendency toward the formation of Mo-rich A15 phase, while the precipitation of the secondary, the assumed plasticizer (Ti)-rich B2 phase is predicted for Al20Ti20Mo20Nb20V20
Summary
THE high entropy alloys—HEA’s are currently one of the most intensively explored directions of studies in materials engineering. In the case of high entropy alloys, by far the most prospective application are the high-temperature structural materials.[5,7] Multiple studies indicate that the mechanical properties of transition metal-based HEAs are comparable, or even superior to the ones of state-of-the-art Ni-based superalloys[3,8] while offering a possibility of tailoring other properties, such as density, in a much more extensive way. Thanks to these exceptional properties, high entropy alloys are nowadays considered potential materials for energy, automotive, aerospace, and nuclear industries.[7,9]
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