Cu + TiB2 composite filler for brazing Al2O3 and Ti–6Al–4V alloy

Abstract Al 2 O 3 and Ti–6Al–4V alloy were brazed using Cu + TiB 2 composite filler, which manufactured by mechanical milling of Cu and TiB 2 powders. Typical interface microstructure of joint was Al 2 O 3 /Ti 4 (Cu,Al) 2 O/Ti 2 Cu + Ti 3 Al + Ti 2 (Cu,Al)/Ti 2 (Cu,Al) + AlCu 2 Ti/Ti 2 Cu + AlCu 2 Ti + Ti 3 Al + Ti 2 (Cu,Al) + TiB/Ti(s.s) + Ti 2 Cu/Ti–6Al–4V alloy. Based on temperature- and time-dependent compositional change, the formation of intermetallics in joint was basically divided into four stages: formation of interfacial Ti 4 (Cu,Al) 2 O in Al 2 O 3 side, formation of Ti 2 Cu, Ti 3 Al, TiB, Ti 2 Cu, and AlCu 2 Ti in layers II and IV, formation of Ti 2 (Cu,Al) and AlCu 2 Ti in layer III, formation of Ti + Ti 2 Cu hypereutectoid organization adjacent to Ti–6Al–4V alloy. TiB in situ synthesized in joint not only acted as low thermal expansion coefficient reinforcement to improve the mechanical properties at room temperature, but also as skeleton ceramic of joint to increase high temperature mechanical properties of Al 2 O 3 /Ti–6Al–4V alloy joint increasing. When the joint containing 30 vol.% TiB brazed at 930 °C and 10 min of holding time, the maximum room temperature shear strength of joint was 96.76 MPa, and the high temperature shear strength of joint was 115.16 MPa at 800 °C.