Mechanical property and corrosion resistance evaluations of Ti-6Al-7Nb alloy brazed with bulk metallic glasses

Exploitation of metallic glass as new brazing filler for Ti-based biomedical alloy was attempted. Ti-6Al-7Nb was used as a brazed material, and candidates of bulk metallic glass brazing filler were Cu₆₀Hf ₂₅Ti₁₅, Mg₆₅Cu₂₅Gd₁₀, Zr₅₅Cu₃₀Al₁₀Ni₅ and Pd ₄₀Cu₃₀P₂₀Ni₁₀- Convergence infrared-ray brazing was conducted for brazing Ti-6Al-7Nb/metallic glass in Ar atmosphere. After brazing, hardness measurement, X-ray tomography, cross-sectional observation, artificial saliva immersion test and tensile test were performed to evaluate brazability, mechanical property and corrosion resistance of the obtained brazing joints. The results of brazing using these metallic glass fillers show that all the metallic glasses were brazable to Ti-6Al-7Nb except for Mg₆₅Cu₂₅Gd₁₀. Mg ₆₅Cu₂₅Gd₁₀. Cu₆₀Hf ₂₅Ti_:5 and their joints collapsed rapidly during immersion test. Zr₅₅Cu₃₀Al₁₀Ni₅ joint was the best in terms of degradation resistance; however, tensile strength was inferior to the conventional one. Pd₄₀Cu₃₀Ni₁₀P ₂₀ filler and Zr₅₅Cu₃₀Al₁₀Ni ₅ filler and their joints did not show any collapse or tarnish during the immersion test. Pd₄₀Cu₃₀Ni₁₀P₂₀ joint showed the excellent properties in terms of both corrosion resistance and tensile strength, which were superior to a joint brazed using Ti-15Cu-25Ni conventional filler. X-ray tomograph indicates that fracture tends to occur in the vicinity of the brazing interface after tensile test. The brazed metallic glass fillers were fully crystallized, excluding Pd₄₀Cu ₃₀Ni₁₀P₂₀ filler. Pd₄₀Cu ₃₀Ni₁₀P₂₀ brazed filler contained maple-leaf like primary dendrite, peritectoid and a few microns interfacial reaction layer in glassy matrix. The results indicated that Pd₄₀Cu ₃₀Ni₁₀P₂₀ is promising brazing filler for dental or biomaterial devices.