Degradable Mg alloy composites using fly ash cenospheres

Abstract The feasibility of fabricating Mg alloy degradable composites with fly ash cenospheres (FACs) using stir casting has been demonstrated. The effects of FAC addition (mass fraction: 0, 2, 4, 6, 8 and 10 wt.%) on the microstructure, mechanical properties and corrosion behavior were investigated using optical microscope, scanning electron microscope, X-ray diffraction, density tests, compression tests, immersion tests and electrochemical measurements. The result shows that the degradable composites are mainly composed of α-Mg, β-Mg ₁₇ Al ₁₂ , Mg ₂ Si and MgO phase, and FAC can refine the grain size. The average measured densities of the FAC/Mg alloy composites are higher than the theoretical values due to the formation of the Mg ₂ Si phase, which are in the range of 1.8843–2.0526 g/cm ³ . The compressive strength of the degradable composites dramatically enhances with the addition of FAC, and the maximum strength is 375 MPa with the 8-wt.% mass fraction, which can be attributed to the refined grains and the formation of massive Mg ₂ Si phase. Furthermore, the corrosion rate of the degradable composites with 10 wt.% FACs shows the highest value of 5.02 g/h in 3 wt.% potassium chloride solution at 80°C, which is three times higher than the corrosion rate of composites without FAC. With the increase in FAC content, more Mg ₂ Si phases formed; thus, micro-galvanic corrosion works well in the composites.