Surface Alloying And Properties Of Aluminum-based Non-solid Solution Elements Under Intense Current Pulsed Electron Beam

In this paper,the "HOPE-?" type High Current Pulsed Electron Beam(HCPEB)was used to irradiate the surface of pure aluminum which was preset W and Mo powders,the irradiation pulses numbers were 15,25 and 35.The change of phase composition and microstructure of the surface of the sample before and after irradiation,were analyzed in detail by using X-ray diffraction(XRD),optical microscope(OM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The micro-hardness of the original and after different HCPEB irradiation times samples was tested.In addition,corrosion resistance properties of these samples were analyzed by electric polarization carve and EIS.Furthermore,the corrosion resistance mechanism induced by HCPEB was emphasized on studying.After HCPEB irradiation,the results of XRD diffraction showed that W and Mo reacted respectively with matrix aluminum,then the corresponding compounds were formed.Further analysis of the microstructure,the surface of the HCPEB after the formation of the classic crater morphology,and disappeared in the subsequent irradiation.TEM and electron diffraction results further confirmed the existence of intermetallic compounds Al5 W,Al4W and Al5 Mo,in addition,with the increase of the number of HCPEB irradiation,a large number of intermetallic compounds will be dispersed on the surface of the material,which has a great effect on improving the surface strength of the material.At the same time,There are a lot of defects in the microstructure of the material after HCPEB irradiation,including dislocations,vacancy clusters and other defects.These defects not only provide a large number of diffusion channels for the diffusion of alloying elements in the process of alloying,but also facilitate the rapid passage of oxygen ions in the corrosion process.The microhardness shows that the surface hardness of the material is improved after irradiation,and the specific reasons for the increase are the fine grain strengthening,solid solution strengthening,second phase dispersion strengthening and dislocation strengthening.With the increase of the irradiation number,the microstructure of the material surface have changed,and the changes of these microstructures have animportant impact on the surface hardness of the materials.Electrochemical corrosion tests show that the corrosion resistance of pure aluminum can be significantly improved by proper HCPEB irradiation.The main reason is that the surface of the alloy layer is formed with a continuous and compact passivation film.In addition,the supersaturated solid solution or intermetallic compound in the local "weakness" occurs in the process of passivation or self healing.The results of EIS analysis show that the samples have good capacitance behavior and protective properties after HCPEB irradiation,which results are consistent with the polarization curves.