Effect of single winding helical electromagnetic stirring on microstructure and mechanical properties of semi-solid Al-Mg2Si in-situ composites

The Al-Mg2Si in-situ composite is a lightweight material with great potential for application in fields such as automotive lightweighting, aerospace, and electronic components. In this research, the modification, semi-solid technology coupled with different types of electromagnetic stirring was applied to regulate the undesirable solidified dendritic microstructure and facilitate the composites’ mechanical properties. The spheroidization and refinement of Mg2Si and α-Al matrix in SM (semi-solid)+RES (rotate electromagnetic stirring) sample and SM+SHES (single winding helical electromagnetic stirring) sample are realized under the effect of fused dendrite arm, the decreased critical nucleate radius, and the increased nucleation rate and extra supercooling degree induced by electromagnetic stirring. The Mg2Si phase in the SM+RES sample and SM+SHES sample are refined by 73.4% and 75.7%, respectively compared to the AC (as-cast) sample. Besides, the single winding electromagnetic stirring can lead to more homogeneously distributed physical fields, lower temperature gradient, and more significant mass transfer, mainly responsible for the more homogeneous distributed reinforced finer Mg2Si particles in the SM+SHES sample. Moreover, both the tensile properties and hardness of modified semi-solid composites are improved through electromagnetic stirring. Compared with RES, the improvement effect of SHES is more excellent. The SM+SHES sample possesses the highest Brinell hardness (124.7 HB), and its quality index of tensile properties is 5.73% and 82.2% higher than that of the SM+RES and AC samples, respectively.