Vacuum brazing of the Gr/2024Al composite and TC4 alloy using AgCuTi filler alloy with Ni-Al interlayer as auxiliary heat source

In vacuum, the Gr/2024Al composite and TC4 alloy were brazed using AgCuTi filler alloy with the assist of Ni-Al interlayer as auxiliary heat source. Because of the thermal explosion synthesis reaction of Ni-Al interlayer, lots of heat can be produced and released, which promises that AgCuTi filler alloy melts and the Gr/2024Al composite and TC4 alloy brazes at low temperature. This method avoids the volatilization of Al in the Gr/2024Al composite at high brazing temperature, keeping the property of the Gr/2024Al composite. According to SEM analysis result, the Gr/2024Al composite reacts with the AgCuTi filler alloy to form a Ti₃AlC₂layer adjacent to the composite, which is the key factor to obtain a perfect joint. A series of Ni-Al compounds form after the thermal explosion synthesis reaction of the Ni-Al interlayer. The particle sizes of Ni and Al have important effects on the thermal explosion synthesis reaction, and then influence the interfacial reaction and the formation of the Ni-Al compounds. The maximum shear strength reaches 13 MPa when the diameter of the Ni and Al particles are 10 μm and 7 μm respectively. Cracks primarily happen in the Gr/2024Al composite and propagate in the composite away from the brazing seam.