Understanding the enhanced corrosion performance of two novel Ti-based biomedical high entropy alloys

The microstructure and corrosion behavior of two novel biomedical high entropy alloys (HEA)s, namely Hf27Nb12Ta10Ti23Zr28 and Hf30Nb14Ta10Ti28Zr18 that were previously designed utilizing machine learning, were investigated in depth. The microstructure of the alloys was determined to be dendritic, with some elemental segregations governed by the solidification kinetics occurring during the arc-melting process. Static immersion experiments were carried out in artificial saliva (AS) and simulated body fluid (SBF) to investigate the ion release behavior of the HEAs and reveal the dissolution kinetics of the passive film forming on the surface. The composition of the corresponding surface oxide layers was examined using X-ray photoelectron spectroscopy, which provided detailed insight into the stability of passive oxide layers and sub-oxide formation. Potentiodynamic polarization experiments performed in AS and SBF at 37 ºC demonstrated that both HEAs exhibit superior corrosion behavior as compared to the CoCrMo alloy, one of the conventional metallic implant materials of choice.