Design And Microstructure Control Of Transition Layer Of Steel/Aluminum Heterointerface Prepared By Laser Additive Manufacturing

Steel/aluminum composite structures were widely used in aerospace,rail transit and other fields due to their high specific strength and light weight.In this paper,taking the steel/aluminum hetero interface as the research object,CoCrNiCux medium-entropy alloy(MEA)transition layer was designed.By controlling the laser process parameters and regulating the metallurgical dilution behavior of the interface,the gradient solid solution of alloy elements at the hetero interface was realized.In this paper,a medium-entropy alloy of CoCrNiCux(x=0.16,0.33,0.75 and 1)was designed firstly,and its microstructure was predicted by Ω-δ criterion and valence electron concentration criterion.The effect of copper content on its microstructure and properties was systematically studied.law of influence.The results show that with the increase of copper content,the entropy alloy in CoCrNiCux system changes from single phase(matrix phase)to dual phase structure(matrix phase+copper-rich phase),and the tensile strength increases from 148 MPa(CoCrNiCu0.33)to 820 MPa(CoCrNiCu),the elongation was correspondingly increased from 1%to 11%.Strengthening mechanisms such as dual phase coordination deformation and misfit dislocations effectively improve the strength and plasticity of the entropy alloys in CoCrNiCu.Secondly,the effect of the variation of Cu content in the CoCrNiCux transition layer on the microstructure evolution behavior at the steel/aluminum heterointerface was investigated.The microstructure and properties of the 316L/CoCrNiCu and CoCrNiCu/AlSi10Mg interfaces were deeply explored,and no cracks occurred at the interfaces on both sides.At the interface of 316L/CoCrNiCu,a solid solution region with Fe concentration gradient was formed,and its shear strength was as high as 380 Mpa.A "rivet"-like Al-Cu solid solution region was formed at the AlSi10Mg/CoCrNiCu interface,and its shear strength was only 70 Mpa.Finally,this paper promotes the gradient solid solution of alloy elements at the heterogeneous interface by controlling the dilution rate of the molten poolto improve the bonding strength of the AlSi10Mg/CoCrNiCu interface.At the same time,the influence of laser process parameters on the interface structure of CoCrNiCu/AlSi10Mg was studied,and the influence law of different dilution rates on the formation of solid solution was mastered,which improved the problem of reducing the bonding strength of the hetero interface due to the existence of metal compound layers,and made the steel/aluminum alloy.The bonding strength of the heterointerface was further improved,and its shear strength was as high as 235 MPa.