Search

Magnesium alloy has the advantages of low density, good damping and noise reduction and good electrical conductivity. It is the lightest metal structural material in applications. However, they are easily corroded due to the low potential of magnesium alloy electrodes, which limits their wide application in industry. At present, surface coating protection technology is one of the most effective methods to improve the corrosion resistance of magnesium alloys. Graphene oxide (GO) has excellent thermal, mechanical and barrier properties, and has broad application prospects in metal protection. GO-based composite coatings can provide a good physical barrier to corrosive media and have become one of the candidate materials for anti-corrosion coatings. In this article, the solutions were proposed for the limitations of single-component GO nanosheets, such as agglomeration and poor compatibility. The preparation methods, types and corrosion protection research progress of GO composite coatings were mainly summarized and its protection mechanism was analyzed in depth. Finally, the future development trend of GO application of magnesium alloy surface corrosion protection coating were prospected. The preparation methods and types of GO composite coatings on magnesium alloys were mainly described. The research progress and corrosion protection mechanism of GO coating on magnesium alloy were summarized.

A novel semi-solid extrusion shear process was proposed based on the idea of "process coupling and shortening process", which can improve the comprehensive mechanical properties by grain refinement. The casting process and solidification process of AZ31 semi-solid forming process were simulated via Anycasting software. The appropriate extrusion parameters were selected by comparing the results of simulation and experiment. The results show that in the deformation zone, the nucleation of AZ31 is promoted by dendrite fragmentation and pressure, leading to the achievement of a fine and uniform structure. The presence of the liquid phase is beneficial to coordinating the deformation during extrusion, reducing the effect of slip and twining on the texture, and thus the extrusion texture is weakened. The maximum basal texture strength is only 5.3 when the shear angle is 180°. Shear angle can further refine grains and improve comprehensive mechanical properties.The best mechanical properties are obtained at the shear angle of 150° with yield strength of 222 MPa, tensile strength of 309 MPa and elongation of 8%.

The tribological properties of garaphene and graphene oxide (GO) as water based additives were investigated for AZ31 Magnesium alloy cold rolling. The morphology and composition of surfaces were characterized by field emission scanning electron microscopy(FESEM) and Raman spectrum. The lubricating mechanism of graphene and graphene oxide(GO) as water-based additives was explored. The results indicate that the best tribological response of the magnesium alloy/steel pairs evaluated is obtained when GO and graphene at a concentration of 0.5%(mass fraction) is added to water. The friction coefficients of graphene nanofluids and GO nanofluids are 0.132 and 0.038, and the wear volumes are 23.1 mm3 and 2.59 mm3. Furthermore, the cold-rolling tests show that the application of GO nanofluids leads to a significant reduction in the rolling force and an improvement in the surface quality of sheets. Under the same testing conditions, the lubricating performance of GO nanofluids are superior to graphene nanofluids, which attributes to the superior dispersion in the water and prominent wetting of the GO nanofluids on the magnesium alloy surface.

The computational material science based on molecular dynamics method is critical for the investigation of the micro-nano scale plastic deformation, which helps to clarify the competition relationship between different plastic deformation mechanisms of magnesium alloys.The mechanism of slip, twinning and grain boundary sliding in magnesium alloys was summarized; the basic principles of molecular dynamics and the potential functions commonly applied to the hexagonal close-packed structure metals were briefly introduced. Moreover,the research progress of plastic deformation mechanism of Mg alloys based on the molecular dynamics was mainly analyzed. Based on the main problems mentioned above, it was pointed out that the development of high-precision potential function for magnesium alloy multiple systems and how to achieve the relationship of multiple scales will be the focused directions in the further research.

The tribological properties of garaphene and graphene oxide (GO) as water based additives were investigated for AZ31 Magnesium alloy cold rolling. The morphology and composition of surfaces were characterized by field emission scanning electron microscopy(FESEM) and Raman spectrum. The lubricating mechanism of graphene and graphene oxide(GO) as water-based additives was explored. The results indicate that the best tribological response of the magnesium alloy/steel pairs evaluated is obtained when GO and graphene at a concentration of 0.5%(mass fraction) is added to water. The friction coefficients of graphene nanofluids and GO nanofluids are 0.132 and 0.038, and the wear volumes are 23.1 mm3 and 2.59 mm3. Furthermore, the cold-rolling tests show that the application of GO nanofluids leads to a significant reduction in the rolling force and an improvement in the surface quality of sheets. Under the same testing conditions, the lubricating performance of GO nanofluids are superior to graphene nanofluids, which attributes to the superior dispersion in the water and prominent wetting of the GO nanofluids on the magnesium alloy surface.

The elevated temperature mechanical properties and fracture mechanisms of as-aged ZM61-xSn(x=0,6,8,10, mass fraction/%)alloys are investigated by optical microscope(OM), X-ray diffraction(XRD), scanning electron microscope(SEM) and high temperature tensile test. The results show that the phase compositions of ZM61-xSn(x=6,8,10)alloys are α-Mg,α-Mn,MgZn2 and Mg2Sn phases. The Sn element can refine the microstructure, improve the high temperature tensile strength, but deteriorate the elongation of ZM61 alloy. The ultimate tensile strength of ZM61-xSn(x=6,8,10) alloys with tensile test at 300℃ are 149,140, 145MPa, compared with ZM61 alloy which is carried out tensile test at the same temperature, the tensile strength increased 26%,17% and 23%, respectively. The elongation of ZM61-xSn(x=0,6,8,10)alloys with tensile test at 300℃ are 39.95%,5.65%,7.01% and 6.33%. The tensile temperature exerts dominating effect for ZM61-xSn(x=6,8,10)alloys on the fracture mechanism. As tensile temperature lower than 220℃, the alloys show transgranular fracture characteristics. The alloys show intergranular fracture characteristics when the tensile temperature is higher than 220℃.