Shear properties of the sapphire/ interlayer / TC4 alloy brazed joints using Ag-Cu-Ti Filler Metals

Ceramic/metal brazing connections faces problems such as poor wetting of the ceramic surface by brazing metal and difficulty in alleviating the residual stress of joints. The effects of Ag-Cu-Ti active brazing metal and the interlayer on the shear properties of the sapphire / TC4 alloy brazed joints were studied. The results show that with the increase of Ti elements content, the melting temperature of Ag-Cu-Ti brazing metals increased slightly, the solid-liquid temperature range remained unchanged. The melted phases of Ag-Cu-3Ti brazing metal mainly included Ag base phase, Ti base phase, crystal phase, etc., the crystal phase included CuTi, Cu₂Ti, Cu₃Ti, CuO, TiO, Cu₂O, Ti₂O, TiAg, etc. A dense metallurgical reaction layer formed between the sapphire and filler metals, its structure was mainly composed of Ag based, Cu based solid solutions and various stable intermetallic compounds. The sapphire/TC4 alloy brazing was completed at 870 ℃/20 min using Ag-Cu-3Ti filler metal and adding 0.2 mm 4J29 sheet, Cu sheet, Mo sheet, titanium fiber porous material, and 2 mm Cu and Mo sheet as the interlayer. The shear strengths of brazed sapphire/TC4 alloy joints were 26.74 MPa, 15.20 MPa, 15.78 MPa, 3.11 MPa, 23.73 MPa, and 30.49 MPa, respectively. The shear strength of brazed sapphire/2 mm Mo sheet/TC4 alloy joints was ideal.