Study On The Microstructure And Properties Of The Scanning Electron Beam Rare Earth Alloy On Surface Of 6061 Aluminum Alloy

In view of the advantages of 6061 aluminum alloy,such as light weight,easy processing,excellent thermal conductivity,etc.,which is applicable to various auto and aircraft parts,aluminum alloy materials often have defects such as wear and corrosion,insufficient hardness and so on.After the surface strengthening treatment by scanning electron beam,the comprehensive properties of the surface can be optimized,which opens up a new field for the surface strengthening of aluminum alloy and effectively expands the application scope of aluminum alloy.In this paper,the surface of 6061 aluminum alloy is directly scanned by electron beam circular scanning method,and then the surface of 6061 aluminum alloy is alloyed by rare earth.The microstructure and mechanical properties of the samples after electron beam treatment are studied by microhardness tester,laser confocal microscope,scanning electron microscope and cft-1 type comprehensive surface property tester.The effects of different parameters on the microstructure,microhardness and wear resistance of the surface modified layer of 6061 aluminum alloy were discussed.After coating 5%rare earth Y₂O₃,La₂O₃,Ce O₂ and 95%Ni powders on the surface of 6061aluminum alloy,the effects of electron beam process parameters on the microstructure and surface properties of the modified layer were discussed.The results show that the surface of 6061 aluminum alloy is composed of melting zone,heat affected zone and matrix after electron beam surface treatment;the microstructure of melting zone is composed of fine strip eutectic Si,strip and needle dendrite,Fe rich phase andα-Al strengthened phase;the microstructure of heat affected zone is composed of coarse strip eutectic Si,α-Al strengthened phase,sheet Fe rich phase and Mg₂Si strengthened phase,and the matrix structure The hardness of the cross-section of the modified layer decreases nonlinearly with the increase of the distance from the surface.The microhardness of the surface is 232.5HV,about 3.6 times of the matrix,and the corrosion resistance is enhanced.The thickness of the modified layer increases with the increase of the electron beam current,the surface hardness increases first and then decreases,and the wear resistance changes uniformly;with the increase of the electron gun moving speed,the thickness of the modified layer decreases gradually,and the surface hardness and wear resistance decrease gradually.After electron beam alloying of 6061 aluminum alloy,the modified layer consists of alloy layer,heat affected zone and matrix.The main structure of the alloying zone is dendrite and cellular crystal composed of Ni-Al compound and a small amount of rare earth compound.The main structure of the heat affected zone is thatα-Al solid solution is equal to Ni-Al compound,and the overall grain structure is smaller than that of the matrix.The matrix structure is mainly composed ofα-Al and black stripe Mg₂Si strengthening phase.The hardness of the sample surface increases first and then decreases with the increase of electron beam flow,and decreases with the increase of electron gun moving speed.Compared with the sample without alloying treatment,the microhardness of the sample surface increases and the wear resistance increases.