Actively brazed alumina to alumina joints using CuTi, CuZr and eutectic AgCuTi filler alloys

Abstract Al 2 O 3 to Al 2 O 3 joints were produced using a one stage active brazing technique based on CuTi, CuZr and AgCuTi active brazing alloys. Single- and double-butt joints were used for microstructural (light and scanning electron microscopy and X-ray diffraction) and mechanical property (double shear test) studies, respectively. The joints produced with CuZr filler alloys (containing 2%, 4%, 6% and 8% Zr, wt%) showed low shear strengths (0.2–0.4 MPa) due to the presence of ZrO 2 at the braze–substrate interface and failed in mode I crack opening. Higher shear strengths of 15–24 and 42 MPa were obtained by using CuTi filler alloys (containing 2%, 4%, 6%, 8% and 10% Ti, wt%) (mode II/mode III dependent on the Ti content) and the eutectic (Ag–27 wt% Cu–5 wt% Ti) alloy, respectively. The high shear strengths were attributed to the small amount of Cu 2 (AlTi) 4 O at the braze–substrate interface and led, in the case of the ternary alloy, to the failure of the substrate rather than the braze (mode III axial splitting).