Fabrication of Ni-free Ti-based bulk-metallic glassy alloy having potential for application as biomaterial, and investigation of its mechanical properties, corrosion, and crystallization behavior

A new Ti-based bulk-metallic glassy (BMG) alloy without Ni was developed in various forms such as melt-spun ribbon and cylindrical rods. Ti metal and Ti-based alloys are well known as biomaterials because Ti has good biocompatibility with the human body. We examined mechanical and chemical properties of a newly developed Ti-based BMG alloy in comparison with pure Ti metal and Ti-6Al-4V alloy, which are used for biomaterials. The new Ti-based BMG (Ti₄₅ Zr₁₀Pd₁₀ Cu₃₁Sn₄) alloy does not contain Ni, Al, and Be elements, which are known to be toxic. The Ti₄₅Zr₁₀ Pd₁₀ Cu₃₁Sn₄ BMG alloy rod with a diameter of 3 mm, which is produced by copper mold casting, exhibits a compressive strength of 1970 MPa and a Young's modulus of 95 GPa. In addition, the Ti₄₅Zr₁₀ Pd₁₀ Cu₃₁Sn₄ BMG alloy shows a supercooled liquid region of 56 K and a reduced glass-transition temperature, T_rg (= T_g/T_l), of 0.56. The high thermal stability of supercooled liquid has enabled the fabrication of a cylindrical rod specimen with a diameter of 4 mm. This alloy exhibits precipitation of a primary nanoscale icosahedral phase upon devitrification followed by the formation of a metastable unidentified phase. Ti₂Cu and Ti₃Sn are stable phases formed in this alloy. The Ti₄₅ Zr₁₀ Pd₁₀ Cu₃₁Sn₄ BMG alloy has a high corrosion resistance and is passivated at a lower passive current density of approximately 10^-2 A/m² compared to those of pure titanium and the Ti-6Al-4V alloy in 1 mass% lactic acid and phosphate-buffered saline solutions at 310 K.