TiZrNbTaMo high-entropy alloy designed for orthopedic implants: As-cast microstructure and mechanical properties

- TiZrNbTaMo high-entropy alloy (HEA) was suggested as potential orthopedic alloy.
- As-cast TiZrNbTaMo HEA consisted of dual bcc phases.
- TiZrNbTaMo HEA exhibits Young's modulus of 153 GPa.
- Compressive yield strength of TiZrNbTaMo HEA reaches to 1390 MPa.
- TiZrNbTaMo HEA manifests excellent corrosion resistance in PBS medium.

Combining the high-entropy alloy (HEA) concept with property requirement for orthopedic implants, we designed a Ti20Zr20Nb20Ta20Mo20 equiatomic HEA. The arc-melted microstructures, compressive properties and potentiodynamic polarization behavior in phosphate buffer solution (PBS) were studied in detail. It was revealed that the as-cast TiZrNbTaMo HEA consisted of dual phases with bcc structure, major bcc1 and minor bcc2 phases with the lattice parameters of 0.3310 nm and 0.3379 nm, respectively. As confirmed by nanoindentation tests, the bcc1 phase is somewhat harder and stiffer than the bcc2 phase. The TiZrNbTaMo HEA exhibited Young's modulus of 153 GPa, Vickers microhardness of 4.9 GPa, compressive yield strength of σy = 1390 MPa and apparent plastic strain of εp ≈ 6% prior to failure. Moreover, the TiZrNbTaMo HEA manifested excellent corrosion resistance in PBS, comparable to the Ti6Al4V alloy, and pitting resistance remarkably superior to the 316L SS and CoCrMo alloys. These preliminary advantages of the TiZrNbTaMo HEA over the current orthopedic implant metals in mechanical properties and corrosion resistance offer an opportunity to explore new orthopedic-implant alloys based on the TiZrNbTaMo concentrated composition.

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