Effect Of Yttrium On Mechanical Properties And Corrosion Ressistance Of Mg-Sc Binary Alloys

As the current social energy shortages,as well as the further development of aerospace,automotive,information and other high-tech industries with large amounts of metal materials,magnesium alloys have received great attention as the lightest structural materials with the highest specific strength.Compared with other engineering structural materials such as steel and aluminum,magnesium alloys still have many shortcomings.The most urgent problem to be solved is the poor mechanical properties and corrosion resistance.Therefore,it is very urgent to develop new magnesium alloy with high strength and high corrosion resistance.According to the literature study and preliminary research results,it was found that the Mg-Sc binary alloy has relatively good mechanical properties and corrosion resistance,but still has much progressive space.In the previous issue,varieties of elements were added as the third element to the Mg-Sc binary system.It was showed that the Y element has a significant improvement on the properties of the alloy.Therefore,this paper mainly discusses the addition of Y to the Mg-Sc binary alloy and five alloys of Mg-5Sc-0.5Y,Mg-5Sc-1Y,Mg-5Sc-2Y,Mg-5Sc-3Y,Mg-5Sc-3.5Y were prepared.The microstructure,mechanical properties and corrosion resistance of Mg-Sc and Mg-Sc-Y alloys were investigated by metallographic microscope?OM?,X-ray diffractometer?XRD?,scanning electron microscope?SEM?,transmission electron microscope?TEM?,universal testing machine,Vickers hardness tester,electrochemical workstation and other characterization methods,and the influence of the addition of Y on the Mg-Sc binary alloy was discussed..The microstructure results showed that the addition of Y element makes the grain refinement of magnesium,and the grain size decreases with the increase of Y content.The six component alloys were all single-phase solid solution,but the Sc and Y elements were distributed in the alloy.Sc was more distributed in the protruding cells of the cell structure,at the same time Y and Mg were more distributed in the groove of the cell structure.The mechanical properties showed that the addition of Y element improves the mechanical properties of Mg-Sc binary alloy.With the increase of Y content,the yield strength was increased from 70MPa of Mg-5Sc to109MPa of Mg-5Sc-3.5Y,elongation was increased from 9%of Mg-5Sc to15.7%of Mg-5Sc-3Y and the hardness was increased from 46.8HV of Mg-5Sc to 60.6HV of Mg-5Sc-3.5Y.Among them,fine grain strengthening and solid solution strengthening mainly caused the increase of alloy yield strength and it was calculated that the contribution of Y element to solid solution strength is higher than that of Sc element.Corrosion resistance results showed that the corrosion rate of the five components of Mg-Sc-Y alloy is smaller than that of Mg-Sc binary alloy,and Mg-5Sc-1Y has the lowest corrosion rate and the best corrosion resistance.This is because the presence of an appropriate amount of Y increases the potential of the matrix Mg and inhibits the occurrence of a cathodic reaction,and Y existed in the surface film tends to form stable Y₂O₃,which is advantageous for enhancing the protective surface film of the magnesium,enhancing the corrosion resistance of magnesium alloys.