An innovative approach for overcoming challenges in the stacked extrusion forming of Mg/Al composite plates

Abstract

This study successfully produced Mg/Al composite plates with Cu transition layer, thus overcoming the limitations of traditional stacked extrusion methods in achieving satisfactory bonding of Mg/Al laminates. The relationship between the microstructure and mechanical properties of composite plates under three extrusion temperatures was revealed, and the deformation process and failure modes of composite plates were investigated. Microstructure observations revealed that the Cu layer exhibited a discontinuous distribution characteristic, and its thicker area effectively impeded the diffusion of Mg and Al elements, thus inhibiting the formation of Mg-Al intermetallic compounds (IMCs). The extrusion temperature did not significantly affect the distribution of the precipitates and texture in the Mg/Al layers. The grain size of the Mg layer showed a growing tendency with rising extrusion temperature, while that of the Al layer remained relatively constant. Mechanical results indicated that the strength of the composite plates decreased as the extrusion temperature increased, which was attributed to the weakening of fine grain strengthening in the Mg layer and dislocation strengthening in the Al layer. Additionally, higher extrusion temperature markedly reduced the elongation of the composite plate, potentially due to accelerated element diffusion at the interface and the discontinuous distribution of the Cu layer, resulting in significant enrichment of IMCs. The Mg-Cu IMCs accumulated and formed in the thicker Cu layer areas, along with Mg-Al IMCs formed in the weaker Cu layer areas, served as crack sources, resulting in cracking of the composite plate during the tensile and eventual failure.