Brazing of 3D printed 6061 aluminum alloy to graphite for high thermal conductivity joints

Joining aluminum alloy to graphite addresses the urgent need for efficient heat dissipation in electronic devices. This study systematically investigates the process of metallizing graphite surfaces using the AgCuTi filler, and analyzes the influence of temperature on the interface and surface characteristics. The study reveals that needle-like TiC phases are formed on the as-metallized layer surface at 900 °C to 950 °C. Subsequently, the as-metallized graphite is brazed to 3D printed 6061 aluminum alloy using the Al-Si-Mg filler, and the microstructure and properties of the joint are analyzed. Results indicate that the joint region mainly contains Al(s,s), ζ-Ag₂Al, θ-Al₂Cu, TiC, Al(s,s) + ζ, and (Al,Si)₃Ti. The shear strength of the 3D printed 6061 aluminum alloy/graphite joints brazed from 560 °C to 590 °C remains relatively stable at about 40 MPa. The thermal conductivity of the as-brazed joints is significantly higher than that of the unbrazed joints. The brazing seam establishes efficient heat transfer pathways from the aluminum alloy to the graphite, improving the thermal conductivity of the joint. The joint brazed at 590 °C for 10 min achieves the highest thermal conductivity of 151.5 W·m⁻¹·K⁻¹ at room temperature and 120.4 W·m⁻¹·K⁻¹ at 500 °C. This study provides an important reference for the application of brazing technology for 3D printed alloy and carbon materials in advanced thermal management systems.