Tin toughens bioimplant titanium alloys through the cocktail effect

However, under certain conditions a brittle omega phase can form, making the material prone to breaking. Whilst it is known that adding tin (Sn) negates this, and makes β-type Ti alloys stronger, the exact mechanics behind this has continued to puzzle scientists. That is until now.

A research team led by Norihiko Okamoto and Tetsu Ichitsubo from Tohoku University's Institute for Materials Research (IMR) has revealed how this occurs. Their revelation came via a systematic investigation using model titanium-vanadium (Ti-V) alloys, which included a combination of experiments 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," explained Ichitsubo.

Just like skillfully blending various drinks often results in a cocktail that is more delicious than imagined, the cocktail effect in the metallurgical field refers to the phenomenon where mixing multiple elemental components in a well-balanced ratio can lead to superior properties beyond expectations.

"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," adds Okamoto. "This discovery underscores the significance of accounting for multi-element interactions not just for biomaterials but also in the broader context of alloy design."

Understanding the finite details of strengthening β-type Ti alloys will help improve biomedical titanium implants, which provide invaluable support for people suffering from degenerative bone condition or aging populations.