Effect of brazing and artificial aging on the microstructure and mechanical properties of a high-strength four-layer laminar aluminum alloy

Abstract

The lightweight design of power battery thermal management systems remains a critical challenge for new energy vehicles. Conventional aluminum alloys often fail to achieve satisfactory mechanical properties after high-temperature brazing (600 °C). To address this limitation, we developed modified aluminum alloys (6061MOD and 3003MOD) and engineered a four-layer laminar structure (4045/3003MOD/6061MOD/3003MOD) for water-cooled plate applications. The microstructural changes and mechanical behavior of these materials were systematically investigated after high-temperature brazing and subsequent aging treatments. Brazing induced substantial grain growth in the 6061MOD core layer, increasing average grain size from 42.3 μm to 90.1 μm. Optimal mechanical properties were achieved through post-brazing treatment: air cooling followed by 200 °C aging for 2 h. This treatment resulted in a tensile strength of 287.1 MPa and a yield strength of 230.5 MPa, primarily attributed to the fine precipitation of Al-Cu, AlMgSiCu (Q), and Mg₂Si reinforcing precipitates. Elemental diffusion analysis revealed Mg penetration depths of 63.7 μm (initial brazing) and 81.9 μm (secondary brazing), with the 3003MOD layer effective blocking of Mg diffusion. This laminated structural design, which integrates components with distinct functional properties, provides an innovative strategy for developing lightweight, high-strength brazed materials while offering critical implications for next-generation vehicle thermal management systems.