| At present, magnesium alloys are potential materials for advanced structuralapplications in various areas with significant advantages of low density, goodelectromagnetic shielding performance, high specific strength and high stiffness incombination with easy recovery. According to some reports, rare earth element is aneffective alloying element in improving the high temperature and corrosion properties ofmagnesium alloys. To our knowledge, there are a few studies concerning theimprovement of the property of rare earth element addition. However, only limited workhas so far been concerned with Sm addition in pure magnesium and its alloys. Rare earthelement Sm has obtained many attentions with less dosage and outstanding function incertain aspect. Sm is group Ce rare earth, its property is similar to other rare earthelements, but it also has some individual physical and chemical properties. Therefore, Smis a potential material such as in special glass, permanent magnetic material of rare earth,modifier of non-ferrous alloy and steel and medicine. The atom size of Sm isapproximately to magnesium, so the solid solubility of Sm in Mg is larger than that ofCerium, lanthanum and neodymium, the maximal value may reach5.8%. Consequently,Sm has important significance in improving the performance of magnesium andmagnesium alloys.In the present study, we studied the effect of different content of Sm in puremagnesium and AZ91magnesium alloy on the organization structure and corrosionbehavior. The surface and cross-sectional morphologies of the specimens after thecorrosion tests were observed with scanning electron microscope (SEM). The corrosionproducts were analyzed by energy dispersive X-ray spectroscopy (EDS) and X-raydiffraction spectroscopy (XRD). Then, the corrosion rate, corrosion products andcorrosion principle were analyzed via open circuit potential, polarization curve andimpedance spectroscopy. The main conclusions are given as follows.(1) After adding the Sm to pure magnesium, the microstructure is composed ofmagnesium matrix and Mg41Sm5. Moreover, the amount of second phase in Mg-Sm alloyincreases with the increase of Mg in Sm. When the content of Sm is under3%, the secondphases are mainly interdendritic distribution; when the content of Sm reaches to3%, the second phases are continuous network structure and the distribution is symmetrical; whenthe content of Sm is higher than3%, the network structure begins to fracture, and thenredistributed in interdendritic.(2) The experimental results of electrochemical corrosion show that the corrosionrate of Mg-Sm alloy immersed in3.5%NaCl is much slower than that of Mg, indicatingthat the addition of Sm may improve the corrosion resistance of Mg.(3) Compared to AZ91, the microstructure and the results of XRD show that thedistribution of second phase in AZ91-Sm alloy has been improved, the second phasedistribution is more continuous and the grain has been refined.It can be seen that theseveral kinds of metal corrosion morphology, After added the rare earth alloy is corrosion,the surface area is reduced a lot, and these traces of corrosion occurs only in a partial areaof the alloy surface, reducing the number of corroded areas, corrosion pit shallower, thusit can be concluded that add samarium AZ91alloy corrosion resistance has beenimproved.（4）After adding the type of content of samarium in AZ91.Its electrochemical corrosiontest results showed that after added samarium in AZ91alloy,its surface hydrogenevolution rate significantly lower than AZ91not added samarium slowed down.Andadded the largest amount of rare earth alloy hydrogen evolution rate is slowest. |
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