Abstract
Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus. However, the current Ti materials used for implant applications exhibit much higher Young’s modulus (50 ~ 120 GPa) than human bone (~30 GPa). This large mismatch in the elastic modulus between implant and human bone can lead to so-called “stress shielding effect” and eventual implant failure. Therefore, the development of β-type Ti alloys with modulus comparable to that of human bone has become an ever more pressing subject in the area of advanced biomedical materials. In this study, an attempt was made to produce a bone-compatible metastable β-type Ti alloy. By alloying and thermo-mechanical treatment, a metastable β-type Ti-33Nb-4Sn (wt. %) alloy with ultralow Young’s modulus (36 GPa, versus ~30 GPa for human bone) and high ultimate strength (853 MPa) was fabricated. We believe that this method can be applied to developing advanced metastable β-type titanium alloys for implant applications. Also, this approach can shed light on design and development of novel β-type titanium alloys with large elastic limit due to their high strength and low elastic modulus.
Highlights
Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus
Β -type Ti alloys developed for implant application can have Young’s modulus in the range of 50 ~ 80 GPa1,8–10, still not low enough to match that of human bone
This points to the looming hope of developing β -type Ti alloys with elastic modulus approaching that of human bone
Summary
The room-temperature XRD results for solution-treated (designated as ST ) and cold-rolled plus annealed (CRA) Ti-33Nb-4Sn specimens are presented in Fig. 1a,b, respectively. A metastable β -type Ti alloy with high ultimate strength (~853 MPa) and ultralow elastic modulus (~36 GPa versus ~30 GPa for human bone) was fabricated In this metastable Ti alloy, β -phase with low content of β -stabilizers is retained at room temperature by high density of dislocations and grain boundaries introduced by cold rolling and annealing treatment. It is this approach and the microstructure that render the bone-compatible low Young’s modulus. Nanometer-sized α -precipitates serve to strengthen the β -matrix acting as dislocation barriers We believe that this approach could be applied to the development of metastable β -type titanium alloys with ultralow Young’s modulus and high strength. Our effort may open a new avenue for design and fabrication of novel metastable β -type titanium alloys for implant applications
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