Evaluation of Long-Term Mechanical and Biological Biocompatibility of Low-Cost β-Type Ti-Mn Alloys for Biomedical Applications

To evaluate the long-term mechanical biocompatibility of Ti-Mn alloys, the microstructures, Young's moduli, and tensile and fatigue properties of the solutionized Ti-8Mn and Ti-13Mn were investigated. In addition, to evaluate the long-term biological biocompatibility of Ti-Mn alloys, the bone formability of the solutionized Ti-12Mn implant was evaluated by animal testing. The solutionized Ti-8Mn and Ti-13Mn consist of equiaxed P-grains with diameters of approximately 420 m and 430 pm, respectively. Moreover, the solutionized Ti-8Mn also contains an athermal <a phase. The 0.2 % proof stress (σ0.2), tensile strength (σb), and elongation of the solutionized Ti-8Mn are 1148 MPa, 1184 MPa, and 2%, respectively. The σ0.2 and σb decrease to 915 MPa and 953 MPa, respectively, and the elongation increases to 7% for the solutionized Ti-13Mn. The higher strength and significantly lower elongation of the solutionized Ti-8Mn are attributed to precipitation of an athermal ω phase. The fatigue strength of the solutionized Ti-8Mn is comparable to that of the aged Ti-6Al-4V ELI in the low-cycle fatigue life region. The striation widths of the solutionized Ti-8Mn and Ti-13Mn are 2.4 m and 7.8 m, respectively. The smaller striation width of the solutionized Ti-8Mn indicates that the crack propagation rate in the solutionized Ti-8Mn is smaller than that in the solutionized Ti-13Mn. The relative bone contact ratio of the solutionized Ti-12Mn increases from 11% to 29% when the implant period increases from 12 to 52 weeks. The relative bone contact ratios of the solutionized Ti-12Mn implant and the commercially pure Ti implant are almost identical for all implantation periods.