Brazing of Cu with Pd-based metallic glass filler

Metallic glass has several unique properties, including high mechanical strength, small solidification shrinkage, small elastic modulus and supercooling state, all of which are well suited as a residual stress buffer for metal and ceramic joining. In the present preliminary study, we demonstrated brazing of Cu rods with Pd₄₀Cu₃₀Ni₁₀P₂₀ metallic glass filler. The brazing was carried out at 873 K for 1 min in a vacuum atmosphere (1 × 10^-3 Pa), and then the specimens were quenched at the rate of 30 K/s by blowing He. The metallic glass brazing of Cu using Pd₄₀Cu₃₀Ni₁₀P₂₀ filler was successful, with the exception that several voids remained in the filler. According to micro-focused X-ray diffraction, no diffraction patterns were observed at both the center of the Pd₄₀Cu₃₀Ni₁₀P₂₀ filler and the Cu/Pd₄₀Cu₃₀Ni₁₀P₂₀ interface. The result showed that the Cu specimens were joined with Pd₄₀Cu₃₀Ni₁₀P₂₀ filler in the glassy state. The tensile fracture strength of the brazed specimens ranged from 20 to 250 MPa. The crack extension from the voids in the Pd₄₀Cu₃₀Ni₁₀P₂₀ filler may have caused the results to be uneven and very low compared to the strength of Pd-based bulk metallic glass.