Development of high modulus TiFeCu alloys for biomedical applications

TiFeCu alloys with higher Young's modulus, hardness and compressive mechanical properties than those of the existing Ti alloys were developed using a d-electrons alloy design method in order to improve Young's modulus, hardness and compressive properties of Ti and existing Ti alloys for use as metallic stents. Their microstructures, Young's modulus, hardness and compressive mechanical properties were investigated both before (as-cast) and after heat-treatments performed under a high-purity argon atmosphere at 1173K for 21.6 and 86.4 ks. The studied TiFeCu alloys consist of the β-Ti phase and dendritic TiFe intermetallic phase. Moreover, the area fraction of the TiFe intermetallic phase increases with increasing atom ratio (Fe + Cu)/Ti of the alloys and with the heat-treatment time. The Young's modulus of the studied TiFeCu alloys increases from 110 GPa (Ti₇₈Fe₁₈Cu ₄ alloy) to 145 GPa (Ti₆₈Fe₃₀Cu₂ alloy) with increasing atom ratio (Fe + Cu)/Ti of the alloys and the area fraction of the TiFe intermetallic phase. However, the Young's modulus is saturated or slightly decreased when the area fraction of the TiFe intermetallic phase is more than 34%. The Vickers hardness of the as-cast alloys increases from 490HV (Ti₇₈Fe₁₈Cu₄ alloy to 550HV (Ti _63.4Fe₃₀Cu_6.6 alloy with increasing atom ratio (Fe + Cu)/Ti of the alloys and area fraction of the TiFe intermetallic phase. On the other hand, the Vickers hardness of the heat-treated alloys is lower than that of the as-cast alloys, despite the increase in the area fraction of the TiFe intermetallic phase after the heat-treatment. The heat-treated alloys have better compressive properties than those of the as-cast alloys and the reported TiFeCu alloys. The compressive strength and strain of the heat-treated Ti67Fe27Cu6 alloys reach to 2131MPa and 24.5%, respectively.