Novel Ti–Zr–Co–Cu–M (M = Sn, V, Al) amorphous/nanocrystalline brazing fillers for joining Ti–6Al–4V alloy

Novel Ti₅₀Zr₃₀Co₁₁Cu₆M₃ (M = Sn, V, Al) amorphous/nanocrystalline alloys with low liquidus temperatures of 1145 K – 1171 K were developed as the brazing filler metals for enhancing the mechanical properties of titanium alloy brazed joints. The Ti–6Al–4V (TC4) joints brazed with these novel Ti-based alloy ribbons at 1233 K for 900 s exhibited typical Widmanstätten structure composed of α-Ti and β-Ti, as well as sporadic ultrafine intermetallic compounds. Among these joints, the TC4/Ti–Zr–Co–Cu–Sn/TC4 joint exhibited relatively low tensile shear strength and impact toughness of 461 MPa and 2.6 J/cm², respectively, due to the concentrated segregation of element Sn in the center of the braze zone. By contrast, the joints brazed with the novel Ti–Zr–Co–Cu–V(Al) fillers showed much improved mechanical properties. The tensile shear strength and impact toughness of the TC4/Ti–Zr–Co–Cu–Al/TC4 joint were enhanced up to 546 MPa and 4.2 J/cm², respectively, suggesting that the present Ti–Zr–Co–Cu–Al amorphous/nanocrystalline filler is a promising brazing material practically applied for joining titanium alloys.