| Magnesium alloys have many advantages such as specific strength and specificstiffness, good electrical shielding performance. Magnesium alloy has become theimportant lightweight materials in the new century and its application prospect is broad.But the chemical properties of magnesium are lively and its equilibrium potential is low. Inaddition, magnesium oxide film is loose with poor properties and will fall off easily, that iswhy the magnesium alloy’s corrosion resistance is poor.In order to improve the corrosion property of magnesium alloy, different amount of Ywas added in the ZK31magnesium alloy, the influence of Y on the magnesium alloycorrosion resistance in NaCl solution and the oxidation resistance atintermediate-temperature was studied. This subject main dedicated to ascertain the role andmechanism of Y in terms of improving the ZK31alloy corrosion property.Mixing different mass fraction of rare earth elements Y with0.5%,1.0%,1.5%,2.0%based on ZK31alloy, five composition ZK31-Y magnesium alloys were prepared. Thephase composition and microstructure of as-cast alloy and extruded alloy were analyzed byusing OM, SEM, XRD, The results showed that, Y can effectively refine the grain ofas-cast alloy, But Y will reduce the solid solution content of Zn in the grains, thuscontributing to the eutectic reaction, forming ternary intermetallic compounds Mg3Y2Zn3.The microstructure changes of ZK31magnesium alloys caused by adding Y wouldinfluence the corrosion resistance of alloys.Choosing two concentrations of NaCl solution, the influence rule of Y on immersioncorrosion weight loss of as-cast and extruded ZK31-Y magnesium alloys were studied. Theinfluence mechanism of the Y on alloy corrosion resistance was analyzed by measuring theelectro-chemical parameters of corrosion potential, corrosion current and the impedance.Results show that, the corrosion rate of as-cast ZK31-Y magnesium alloys immersed inneutral NaCl solution promoted by rare earth Y, electrochemical corrosion potential shiftednegatively, the impedance and corrosion resistance reduced. The corrosion rate of extrudedmagnesium alloys was significantly higher than that of as-cast magnesium alloy due tointeraction of galvanic corrosion and intergranular corrosion. In addition, In addition, theincrease of concentration of Cl-will also accelerate the corrosion rate of magnesium alloy. Uses elevated constant temperature oxidation method, the corrosion of as-cast andextruded ZK31-Y magnesium alloys oxide weight gain and the influence rule of Y onoxide weight gain were studied. The influence mechanism of the Y on alloy oxidationcorrosion resistance was analyzed by establishing oxidation kinetics model and calculatingoxidizing reaction speed constant. Results show that, the oxidation process is divided intotwo stages: Interface reaction controlling the oxidation process at initial period of oxidation,The ZK31-Y magnesium alloys’ oxidation rule conform to the straight line equation,oxidation rate increases with the increase content of rare earth Y. Diffusion reactioncontrolling the oxidation process at later period of oxidation, oxidation weight increase inline with square rule of1#magnesium alloy without Y and the oxidation weight increasein line with cubic law of2#magnesium alloy with0.5wt.%Y and5#magnesium alloywith2.0wt.%Y.Through this research work, finding suitable adding amount of Y that can improve thecorrosion resistance of wrought ZK31magnesium alloy, basically illustrate the reasons ofY influence corrosion resistance of ZK31magnesium alloy, has important guidingsignificance to improve the corrosion resistance of magnesium alloys by use rare earth Y. |
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