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The eletrodeposition nano-TiO2/Ni composite coating on AZ91PH Mg alloy was prepared using the nano-TiO2 as the second phase particles. The corrosion resistance of the composite coating was measured by the static immerging corrosion test and the polarization curve test. The result shows that the corrosion resistance of the composite coating was better than that of Mg alloy. The corrosion resistance of the composite coating was optimal when the content of nano-TiO2 in the plating solution was 10g/l-15g/l.

The Ni-SiO 2 nano-composite coatings were fabricated by electrodeposition on the AZ91HP magnesium alloy surface, in which nano-SiO 2 was chosen as the second-phase particulates. The microstructure was observed by SEM, the microhardness was measured by micro-density tester and the wear resistance was estimated by M-200 type block-on-wheel dry sliding frication and wear tester. The results indicate that the Ni-SiO 2 nano-composite coatings with uniform crystalline, dense structure can be obtained on AZ91HP magnesium alloy. The interface morphology shows that the combination between the nano-composite coatings and magnesium alloy is fine. The maximum value of microhardness reaches HV367 when the content of nanoparticles is 10 g/L, however, the microhardness of the pure nickel coatings is HV274 and the hardness of magnesium alloy only is HV82.7. The frication and wear experiments reveal that the wear resistance of nano-composite coatings are improved obviously compared to magnesium alloys and pure nickel coatings, which are induced by dispersive strengthening effect and grain refining effect. The main wear mechanism of nano-composite coating is abrasive wear, the wear mechanism of magnesium alloys is adhesion wear, and that of pure nickel coating is exfoliation wear, respectively.

A 3-dimensional electromagnetic-thermal numerical simulation of cold crucible levitation melting method considering surface-to-surface heat radiation is performed by adopting finite element method. Direct area integration method and hemi-cube method are adopted to calculate the surface-to-surface heat radiation separately. Results of considering surface-to-surface heat radiation are compared with those considering surface-to-ambient heat radiation, and neglecting heat radiation. The temperature difference between surface-to-ambient and surface-to-surface is relatively small, hence it is accurate enough to take surface-to-ambient heat radiation into consideration only for the calculation of temperature distribution of EMCC melting method.