| Recently,rare earth magnesium alloys have attracted much attention due to their excellent mechanical properties and biocompatibility.The WE43 Mg alloy,for example,contains yttrium(Y)and neodymium(Nd),which helps to improve the anticorrosion properties,and is an attractive biomedical rare earth Mg alloy.However,rare earth medical Mg alloys still have the problem of poor corrosion resistance in human body environment,which inevitably leads to premature loss of mechanical and biological properties of implants in the process of use.As an efficient surface treatment technology in recent years,pulsed laser surface micro-texture technology can change the surface morphology,physical and chemical properties and corrosion properties of materials,showing a unique charm.In this paper,WE43 Mg alloy was micro-textured by pulsed laser to improve its corrosion resistance in simulated fluid environment.The research contents are as follows:The surface of WE 43 was microfabricated by the short pulse laser,and the different laser power structures were observed by XRD,SEM,EDS and metallographic microscopy.The results show that the surface of WE43 Mg alloy showed a multi-level microstructure after pulsed laser microtexture treatment in air.At the edge of the processing area,many remelted nanoparticles are formed.Meanwhile,a white oxide film composed of oxides such as Mg O and Y2O3 is formed on the sample surface.With the increase of laser power,the proportion of O content on the sample surface gradually increases,and the density of the oxidized film also increases.The electrochemical test results show that the corrosion resistance of pulsed laser microtextured samples has been improved to some extent.The corrosion potential of the as-cast sample was-1.915V,and the corrosion current density was 1382μA/cm~2.After the pulse laser texture treatment,the corrosion potential of the sample was increased to-1.788V,and the corrosion current density was 326.5μA/cm~2.Based on the microstructure characterization and electrochemical test results,the corrosion mechanism model of WE43Mg alloy treated by PLST was proposed from the perspective of microstructure.After pulsed laser ablation,an oxide layer composed of Mg O isooxide is formed on the surface of the magnesium alloy sample.Due to the blocking effect of the oxide layer,the magnesium alloy matrix avoids direct contact with the solution at the initial stage of immersion.The sample surface is basically free of cracks and local pitting corrosion.The results of electrochemical corrosion in simulated body fluid(SBF)of WE43 Mg alloy soaked for different days showed that with the increase of soaking time,the corrosion resistance of the laser treated samples in SBF increased.The high-power pulsed laser microfabrication samples exhibited the best corrosion resistance in SBF under the same immersion time.The corrosion potential of WE43 Mg alloy soaked under 24W was increased from-1.788V to-1.556V,and the corrosion current density was reduced to 8.316μA/cm~2.Based on the test results,we propose a corrosion mechanism of WE43 Mg alloy by PLST treatment after immersion.The PLST treated sample was soaked to form a double protective structure.In the early stage of immersion,the oxide layer plays a dominant protective role,while the deposition layer plays a dominant protective role in the late immersion period.Figure[30]table[9]reference[82]... |
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