The influence of the thickness, phase composition, and morphology of AlₓCuᵧ intermetallic compound (IMC) interlayers on the mechanical integrity of Al/Cu bimetallic electrical connectors was investigated through experimental simulation under dynamic and static conditions. Al/Cu joints were produced by continuous-drive friction welding (CDFW) and subsequently modified either by extending friction time (dynamic conditions) or by post-weld heat treatment at 325 °C for 1 and 12 h (static conditions). In the as-welded state, joints exhibited discontinuous Al₂Cu interlayers with thicknesses below 0.5 µm. Under static conditions, IMC interlayers evolved into continuous multilayered structures (Al₂Cu, AlCu, and Al₄Cu₉) with thicknesses up to ~7.3 µm, while dynamic conditions produced thinner and less uniform interlayers (<1.6 µm), typically consisting of continuous Al₂Cu and discontinuous Al₄Cu₉. Despite the greater thickness and structural complexity of IMC interlayers formed under static conditions, these joints consistently exhibited higher ultimate tensile strength and comparable or improved elongation at break relative to dynamically formed joints. The results indicated that IMC interlayer thickness alone was not a reliable parameter for assessing mechanical integrity. Instead, phase composition, morphology, and thickness distribution must be considered as well. From a forensic engineering perspective, variations in IMC thickness between central and peripheral regions, thickness non-uniformity, and phase constitution provide valuable indicators of manufacturing conditions and service history. These findings highlight the importance of comprehensive interfacial characterization for improving the accuracy of failure analysis and root cause identification in Al/Cu systems.
Invited Lectures