Vanadium-free Ti-based high- and medium-entropy alloys as next-generation biomedical implant materials: a critical review

Nada Hamad; Ahmed Abbas; Rusul Ghadban; Mohammed Abdulrehman; Khairunisak Abdul Razak; Ahmed Hafedh Mohammed; Ali Flayyih; Ali Salman; Nada Hamad; Ahmed Abbas; Rusul Ghadban; Mohammed Abdulrehman; Khairunisak Abdul Razak; Ahmed Hafedh Mohammed; Ali Flayyih; Ali Salman

doi:10.3934/bioeng.2026007

AIMS Bioengineering

2026, Volume 13, Issue 1: 136-167. doi: 10.3934/bioeng.2026007

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Review

Vanadium-free Ti-based high- and medium-entropy alloys as next-generation biomedical implant materials: a critical review

1.
Project and Construction Division, Mustansiriyah University, Baghdad, Iraq
2.
Al-Mustafa University College, Baghdad, Iraq
3.
Department of Materials Engineering, Engineering College, Mustansiriyah University, Baghdad, Iraq
4.
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Malaysia

Received: 18 February 2026 Revised: 13 March 2026 Accepted: 19 March 2026 Published: 24 March 2026

Load-bearing biomedical implants in severe physiological environments must compromise mechanical compatibility, corrosion resistance, and long-term biocompatibility. The fear of the long-term liberation of vanadium and aluminum has provoked the creation of vanadium-free options, despite Ti-6Al-4V remaining clinically viable. This has proved promising, with high- and medium-entropy alloys (HEAs/MEAs) of titanium containing non-toxic two stabilizing elements such as Nb, Ta, Mo, and Zr. Concentrating on the interdependent nature of alloy composition, microstructural development, phase stability, corrosion characteristics, ion release, and biological response, the present critical review article discusses vanadium-free Ti-based HEAs/MEAs and their potential use in biomedical implants. Ti-based HEAs/MEAs have been found to possess low elastic modulus values, corrosion resistance (owing to the presence of multicomponent passive oxide films), and good in vitro cytocompatibility compared to conventional Ti-6Al-4V alloys. This review highlights that microstructural heterogeneity, particularly in additively produced alloys, may have a significant influence on corrosion and biological performance, and that high configurational entropy is not sufficient to ensure improved performance. The challenges that are left to overcome include the lack of standardized testing procedures and long-term in vivo validation. This review presents research priorities so that the clinical translation of vanadium-free Ti-based HEAs/MEAs to be used in load-bearing applications is carried out safely.
- Vanadium-free alloys,
- high-entropy alloys,
- medium-entropy alloys,
- biomedical implants,
- corrosion resistance,
- biocompatibility,
- complex concentrated alloys,
- multi-principal element alloys
Citation: Nada Hamad, Ahmed Abbas, Rusul Ghadban, Mohammed Abdulrehman, Khairunisak Abdul Razak, Ahmed Hafedh Mohammed, Ali Flayyih, Ali Salman. Vanadium-free Ti-based high- and medium-entropy alloys as next-generation biomedical implant materials: a critical review[J]. AIMS Bioengineering, 2026, 13(1): 136-167. doi: 10.3934/bioeng.2026007

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Abstract

Load-bearing biomedical implants in severe physiological environments must compromise mechanical compatibility, corrosion resistance, and long-term biocompatibility. The fear of the long-term liberation of vanadium and aluminum has provoked the creation of vanadium-free options, despite Ti-6Al-4V remaining clinically viable. This has proved promising, with high- and medium-entropy alloys (HEAs/MEAs) of titanium containing non-toxic two stabilizing elements such as Nb, Ta, Mo, and Zr. Concentrating on the interdependent nature of alloy composition, microstructural development, phase stability, corrosion characteristics, ion release, and biological response, the present critical review article discusses vanadium-free Ti-based HEAs/MEAs and their potential use in biomedical implants. Ti-based HEAs/MEAs have been found to possess low elastic modulus values, corrosion resistance (owing to the presence of multicomponent passive oxide films), and good in vitro cytocompatibility compared to conventional Ti-6Al-4V alloys. This review highlights that microstructural heterogeneity, particularly in additively produced alloys, may have a significant influence on corrosion and biological performance, and that high configurational entropy is not sufficient to ensure improved performance. The challenges that are left to overcome include the lack of standardized testing procedures and long-term in vivo validation. This review presents research priorities so that the clinical translation of vanadium-free Ti-based HEAs/MEAs to be used in load-bearing applications is carried out safely.

Acknowledgments

The authors would like to thank Mustansiriyah University for their continuous support and providing the facilities required to complete this study. The university environment and facilities played an important role in the success of this study.

Conflict of interest

The authors declare no conflicts of interest.

Author contributions

Conceptualization, Mohammed Abdulrehman and Khairunisak Abdul Razak; methodology, Mohammed Abdulrehman, Ahmed Abbas, and Khairunisak Abdul Razak; literature survey and data curation, Nada Hamad, Rusul Ghadban, Ahmed Mohammed, Ali Flayyih, and Ali Salman; formal analysis and critical interpretation, Mohammed Abdulrehman, Ahmed Abbas, and Khairunisak Abdul Razak; visualization and figure preparation, Ali Flayyih, Rusul Ghadban and Ahmed Mohammed; writing—original draft preparation, Nada Hamad and Mohammed Abdulrehman; writing—review and editing, Mohammed Abdulrehman, Ahmed Abbas, Khairunisak Abdul Razak, and Ali Salman; supervision, Mohammed Abdulrehman and Khairunisak Abdul Razak; project administration, Mohammed Abdulrehman. All authors have read and agreed to the published version of the manuscript.

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