Effects of Niobium and Vanadium on the Properties of Porous TiMoCuAg High-Entropy Alloys

Powder metallurgy was used to create porous TiMoCuAgV HEA (VHEA) and TiMoCuAgNb HEA (NbHEA) using 0, 10, and 20 wt.% from ammonium hydrogen carbonates (AHCs) as a space holding material. Samples were mixed with AHCs as a foaming agent. All samples were compacted at 400 MPa and sintered at 1250(o)C. X-ray diffraction, scanning electron microscopy, and energy dispersive analyses were performed for phase identification, microstructure observation, and elemental composition, respectively. Fabricated HEAs density values were estimated according to Archimedes' principle. Also, hardness and Young's modulus were determined. The addition of vanadium (V) was shown to exceed that of niobium (Nb) in increasing the HEA Young's modulus without AHCs. The corrosion characteristics of the prepared HEAs in corrosive media were estimated by the weight loss (WL) method, indicating good improvement by adding either V or Nb. The findings showed that the 10-NbHEAs in SBF had the highest improvement values, where the CR value was 0.94 mm/y lower than other investigated media. Additionally, 10-VHEAs in a simulated body fluid solution (SBF) and hydroxyapatite (HA) corroded more rapidly than 10-NbHEAs. After the corrosion test, the surface morphology showed a protective layer for 10-NbHEAs in SBF media. Also, the surface morphology is well-defined as smooth and uniform in HA media for 10-NbHEAs and 20-NbHEAs, which agrees with WL and corrosion rate values. Generally, VHEAs have higher corrosion resistance than NbHEAs.