Modification of structural, mechanical, corrosion and biocompatibility properties of Ti₄₀Zr₁₀Cu₃₆Pd₁₄ metallic glass by minor Ga and Sn additions

Ti₄₀Zr₁₀Cu₃₂Pd₁₄Ga₄ and Ti₄₀Zr₁₀Cu₃₂Pd₁₄Sn₄ (in at%) bulk metallic glasses (BMGs) with different geometries (wedges, rods, ribbons and discs) were prepared by suction casting, melt spinning and splat quenching, respectively. For comparison, the reference Ti₄₀Zr₁₀Cu₃₆Pd₁₄ BMG was cast as a rod with 2 mm diameter and in wedge-shaped form. High-energy X-ray diffraction measurements yielded a critical casting thickness of 2.4, 2.1 and at least 4 mm for the reference, Ga-containing, and Sn-containing BMGs, respectively. The extension of the supercooled liquid region of about 50 K, measured for the glassy rods and ribbons by differential scanning calorimetry, is larger than that of only 20 K found for the splat-quenched discs. As to the alloys’ mechanical properties, the Ti₄₀Zr₁₀Cu₃₆Pd₁₄ glassy rods deform plastically in compression up to a strain of 3.8% and possess a Young’s modulus of 78 GPa. The Sn- and Ga- containing BMG rods reach respectively a plastic strain of 6.1% and 4.7%, and a Young’s modulus of 72 and 63 GPa. Corrosion tests were performed by electrochemical experiments, and the highest pitting resistance was observed for Ti₄₀Zr₁₀Cu₃₂Pd₁₄Sn₄ (pitting overpotential η_pit = 446 mV) compared to Ti₄₀Zr₁₀Cu₃₂Pd₁₄Ga₄ (379 mV) and Ti₄₀Zr₁₀Cu₃₆Pd₁₄ (183 mV). The results of live/dead assay and cell viability revealed excellent biocompatibility for the Ga-containing BMGs.