The Study Of Magnesium Alloy Surface Modification By High Current Pulsed Electron Beam

Magnesium alloy is a light weight requirement, great development potential "greenengineering material”, but poor surface properties limit its range of applications. Thissubject try using high current pulsed electron beam (HCPEB) irradiation to treatmagnesium alloy surface, study the surface morphology and properties of magnesium alloyafter treatment.Mathematical and physical model of the dynamic temperature field of HCPEBmodification process was built, used finite element software to simulate and analyze thetemperature field evolution of HCPEB irradiated pure magnesium process, the resultshowed that about13μm depth material surface was melted, the surface maximumtemperature was about1130°C, the heating rate and cooling rate was109°C/s and106°C/s,heat-affected zone was about43μm depth after single-pulse electron beam irradiated in theenergy25KeV. Then carried out pure magnesium and magnesium alloy HCPEBmodification experiments, the energy was25KeV and pulse times were10,15and20.After HCPEB irradiation, the surface of pure magnesium and AZ31magnesium alloyformed typical crater morphology, with the times of pulses increased, the number of craterson the surface multiplied gradually, the different macro morphology was that missionspherical and long cellular. According to simulation analysis results, the formation ofcraters were due to the subsurface temperature exceeded the boiling point of materialsduring the irradiation process, then vaporized, boiled and bubble erupted from subsurfacecaused “volcanic eruptions like crater”. Observed the microstructure of the cross sectionafter irradiation, the remelted layer is about15μm, this is consistent with the results of thesimulation, and increased in the number of pulses had no effect on the depth of theremelted layer, there was grain refinement at the junction of remelted layer and substrate.The change of XRD analysis showed that there was residual compressive stress afterirradiated, stress value exceeds the material yield strength, the stress values increased whenthe pulse times changed. The surface hardness of pure magnesium improved by70%andAZ31increased by20%, the wear volume decreased, the corrosion potential improvedafter irradiation. High current pulsed electron beam irradiation is effective to improve thesurface properties of magnesium alloy.Tried a new AZ31magnesium surface modification method that combination ofthermal spraying aluminum and high current pulsed electron beam irradiation, andformatted metallurgical bond between the coating and substrate after modification, the binding between the coating and substrate enhanced, the surface micro hardness improved;Also carried a combination modification method that magnetron sputtering aluminum filmand the HCPEB irradiation, formed super saturated solid solution of aluminum andmagnesium on the surface, achieve the fast alloying, surface micro hardness increased by130%, the modified samples’ corrosion potential increased, corrosion current decreased,and the corrosion resistance improved.