Effect of bonding time on the microstructure and mechanical properties of graphite/Cu-bonded joints

The increasing serious heat dissipation problem faced by electronic equipment used in airplanes makes studies on new heat dissipation components urgent. The diffusion bonding of graphite and Cu was successfully realized by a Ti/Ag/Nb interlayer at the bonding conditions applied (850°C, 4 MPa with bonding time varying from 30 to 90 min). The influence of bonding time on the microstructure and mechanical properties of the joints was studied. When the bonding time was 30 min, the typical microstructure of the joints was as follows: graphite/TiC reaction layer/residual Ti layer/Ti2Ag layer/TiAg/Ti[Ag,Nb]/Cu. As the bonding time increased, the thickness of the residual Ti layer decreased, whereas the thickness of the Ti[Ag,Cu] layer increased. When the bonding time was extended to 90 min, Ti-Cu intermetallic compounds were detected adjacent to the Cu. The shear strength showed an increasing trend with the extension of the bonding time. When the bonding time was 90 min, the maximum shear strength of the joints was 13.4 MPa.