Reviewed by Lexie CornerJun 5 2024
A study team led by Norihiko Okamoto and Tetsu Ichitsubo from Tohoku University’s Institute for Materials study (IMR) discovered that a brittle omega phase can emerge under certain conditions, making the material more likely to shatter. The study has been published in the journal Acta Materialia.
Stem as artificial hip femoral components. The ternary interaction of titanium (Ti), β-stabilizing elements like niobium (Nb) and vanadium (V), and tin (Sn) plays a crucial role in determining the phase stability of the biocompatible Ti alloys. Image Credit: Tohoku University.
Beta(β)-type titanium (Ti) alloys are known for their strength, formability, and durability in hostile conditions. This, along with their superior biocompatibility, has made them ideal candidates for implants and prostheses ranging from joint replacement to stents.
However, a brittle omega phase might emerge under some conditions, making the material more susceptible to breaking. Although scientists understand that adding tin (Sn) strengthens β-type Ti alloys, the specific mechanism remains unclear. That was until now.
The researchers conducted a comprehensive inquiry utilizing model titanium-vanadium (Ti-V) alloys, comprising experimental and theoretical analyses.
Our findings reveal that the multi-element interaction between Ti, V, and Sn, coupled with the anchoring effect of Sn atoms, work together to completely suppress the formation of the detrimental omega phase, exemplifying the so-called cocktail effect.
Tetsu Ichitsubo, Institute for Materials Research (IMR), Tohoku University
In metallurgy, the cocktail effect describes how combining several elements in a well-balanced ratio can produce superior properties that surpass expectations—like mixing drinks to get a tastier cocktail.
This cocktail effect is a prime example of the phenomena observed in high-entropy materials, highlighting the importance of considering multi-element interactions in alloy design. This discovery underscores the significance of accounting for multi-element interactions not just for biomaterials but also in the broader context of alloy design.
Norihiko Okamoto, Institute for Materials Research (IMR), Tohoku University
Understanding the intricacies of strengthening β-type Ti alloys can help enhance biomedical titanium implants. These implants provide crucial support for people suffering from degenerative bone conditions or aging populations.
The study, published in Acta Materialia on April 29th, 2024, was heavily influenced by the pioneering work of Shuji Hanada and Naoya Masahashi, emeritus professors of IMR.
Journal Reference:
Okamoto, L., N., et al. (2024) Why is neutral tin addition necessary for biocompatible β-titanium alloys?–Synergistic effects of suppressing ω transformations. Acta Materialia. doi:10.1016/j.actamat.2024.119968