Effect of Si content on microstructure and compressive properties of open cell Mg composite foams reinforced by in-situ Mg2Si compounds

The open-cell Mg-xSi (x = 1, 5, 9 wt%) foams reinforced by in-situ Mg2Si compounds were prepared by pressure infiltration process. The optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the microstructure, chemical components and phase compositions of the foams, respectively. Compressive strength and energy absorbing characteristics of the foams containing varied Si additions were assessed via compressive test. The experimental results exhibit that the microstructure of the foams is depending on Si content. Mg-1Si foams are mainly composed of eutectic Mg2Si and alpha-Mg, while Mg-5Si and Mg-9Si foams mainly consist of the primary Mg2Si, eutectic Mg2Si and alpha-Mg. The compressive strength of the foams is elevated initially and then decreased when the Si content is increased from 1 to 9 wt%, but the energy absorption capacity is reduced with the increase of Si content. The related mechanism was discussed and a schematic diagram was drawn to reflect the role of coarse primary Mg2Si in fracture behavior of the foams.