Brazing of 6061 aluminum alloy/Ti–6Al–4V using Al–Si–Cu–Ge filler metals

Al–8.4Si–20Cu–10Ge and mixed rare-earth elements (Re) containing Al–8.4Si–20Cu–10Ge–0.1Re filler metals were used for brazing of 6061 aluminum alloy/Ti–6Al–4V. The addition of 20 wt.% copper and 10 wt.% germanium into the Al–12Si filler metal lowered the solidus temperature from 586 °C to 489 °C and the liquidus temperature from 592 °C to 513 °C. The addition of 0.1 wt.% rare-earth elements into Al–8.4Si–20Cu–10Ge alloy caused remarkable Al-rich phase refinement and transformed the needle-like Al2Cu intermetallic compounds into block-like shapes. Shear strengths of the 6061 aluminum alloy/Ti–6Al–4V joints with the two brazing filler metals, Al–8.4Si–20Cu–10Ge and Al–8.4Si–20Cu–10Ge–0.1Re, varied insignificantly with brazing periods of 10–60 min. The average shear strength of the 6061 aluminum alloy/Ti–6Al–4V joints brazed with Al–8.4Si–20Cu–10Ge at 530 °C was about 20 MPa. Rare-earth elements appeared to improve the reaction of the Al–8.4Si–20Cu–10Ge filler metal with Ti–6Al–4V. The joint shear strength of the 6061 aluminum alloy/Ti–6Al–4V with Al–8.4Si–20Cu–10Ge–0.1Re reached about 51 MPa.