Formation and properties of centimeter-size Zr-Ti-Cu-Al-Y bulk metallic glasses as potential biomaterials

A series of Ni-free (Zr_0.5Ti_0.02Cu_0.38Al_0.1)_100-xY_x (x = 0, 1, 2, 3 and 5 at.%) bulk metallic glasses (BMGs) with outstanding glass-forming ability (GFA) were synthesized by copper mold casting and the effects of yttrium addition on glass-formation, thermal stability, mechanical properties and in vitro biocompatibility of the BMGs were investigated. It was found that the addition of 1-3 at.% Y greatly enhanced the GFA and thermal stability of the Zr₅₀Ti₂Cu₃₈Al₁₀ alloy. The critical diameter (d_c) increased from 5 mm for the Y-free alloy to 20 mm by 2 at.% Y addition. The supercooled liquid region (ΔT_x) of the Zr-based alloys was also enlarged to 60-71 K by the 1-3 at.% Y doping from 59 K for the base alloy. The compressive strength and plastic strain decreased gradually with the increase in Y content, while the Zr-based BMGs containing 0-3 at.% Y still exhibited high yield strength of about 1750-1800 MPa and compressive plasticity. The Zr-based BMGs also exhibited Young's moduli of 82-89 GPa, which are lower than that of Ti-6Al-4V alloy. Cell proliferation and cytotoxicity of mouse MC3T3-E1 pre-osteoblast on the Zr-based BMGs demonstrated good biocompatibility comparable to Ti-6Al-4V alloy. The combination of outstanding GFA and good mechanical properties and in vitro biocompatibility makes these Ni-free Zr-based BMGs promising as biomedical materials.