The Behaviour of Gum Metal (Ti‐36Nb‐2Ta‐3Zr‐0.3O wt.%) During Superelastic Cycling

Abstract

Metastable beta titanium alloys, such as Gum Metal (Ti-36Nb-2Ta-3Zr-0.3O wt.%), have received significant attention from the biomedical field over the last decade due to their low elastic modulus. Despite initial scepticism, it is now widely accepted that these alloys undergo a stress-induced transformation when subjected to an applied load, forming an orthorhombic martensite phase within the beta matrix. The reversible nature of this transformation gives rise to superelasticity, which is of significant interest for engineering applications outside of the biomedical industry. However, little is known as to the stability of the superelastic behaviour with respect to repeated load cycling. Here the response of Gum Metal during superelastic cycling was studied in situ, using high energy synchrotron diffraction. The material was observed to accumulate permanent damage with every cycle and the critical stress required for transformation decreased. The diffraction data was used to track the evolution of the martensite phase, both as a function of applied stress and cycle number. The martensite that formed was highly textured, with two independent orientations observed on each Debye-Scherrer ring. These orientations formed at different applied stresses and had different volume fractions at the peak stress. The volume fraction at the peak stress of all martensite orientations increased with cycling, which is believed to increase the defect concentration in the material and hence influence the deformation behaviour.

Biomedical Applications of Titanium Alloys: A Comprehensive Review

“…Ti-24Nb-4Zr-8Sn β Joint replacement [104] Ti-9Mn β Joint replacement [105,106] Ti-6Mn-4Mo β Joint replacement [106] Ti-10Fe-10Ta-4Zr β Joint replacement [107,108] Ti-12Cr β Joint replacement [109] Ti-11Cr-0.xO β Joint replacement [110] Ti-36Nb-2Ta-3Zr-0.3O β Joint replacement [111] Ti-24Nb-0.5O β Joint replacement [112] Ti-24Nb-0.5N β Joint replacement [112] Ti-23Nb-0.7Ta-2Zr β Joint replacement [113] Ti-23Nb-0.7Ta-2Zr-1.2O β Joint replacement [113,114] Ti-12Mo-6Zr-2Fe β Joint replacement [115] NiTi (Nitinol) Cardiovascular, dental, joint replacement [116] Ti-30Zr-xMo Joint replacement [117] Materials 2024, 17, x FOR PEER REVIEW 9 of 42 Despite the wide range of possible alloys, commercially pure titanium grade 2 and Ti-6Al-4V grade 5 are used in more than 95% of all titanium biomedical devices. Also widely used in the biomedical field are ELI (Extra-Low Interstitials) alloys, whose main chemical composition is similar to that of the above alloys, but with very low levels of interstitial elements.…”