Improvement of the Mechanical Properties of the Diffusion-Bonded 2024 Aluminum Alloy through Post-Weld Heat Treatments

In this study, 2024 aluminum alloy was diffusion bonded to identify the effect of the bonding temperature, applied pressure, and heating time on the microstructure, hardness, and bonding strength. The shear strength increased from 62.5 MPa to 81.2 MPa along with the rise in bonding temperatures from 440 °C to 490 °C. The bonding strength rose from 62.5 MPa to an optimal value of 81.2 MPa by extending the bonding time from 30 min to 240 min at a bonding temperature of 490 °C and a constant pressure of 5 MPa. In addition, various post-weld heat treatments for diffusion-bonded joints were also performed to improve the bond quality. After the T6 or T4 post-weld heat treatment, the hardness at the bonding interface and the substrate increased due to the precipitation of Al2Cu. Post-weld T4 and T6 heat treatments increased the interface microhardness from 106.3 Hv to 138.25 Hv and 130.6 Hv, respectively. The bonding strength of the AA2024 was significantly improved up to 124.5 MPa and 164.3 MPa by the T4 and T6 heat treatments, respectively.