The Research On Ti/Al Dissimilar Metal Electron Beam Melting Brazing Compound Welding

Aluminum lithium alloys and titanium alloys have been widely used in aerospace and aerospace industries.In recent years,the manufacturing industry is in the pursuit of light structure,structural function integration and low cost design and manufacture,so the composite structure of aluminum lithium alloy and titanium alloy has great application prospects.However,due to the difference of the physical and chemical properties of titanium and aluminum,and the chemical reaction between the two is very easy to form brittle intermetallic compounds,so this gives Ti/Al welding caused some difficulties.This test uses electron beam melting soldering method.By using the high aspect ratio and the energy of the electron beam,a reliable Ti/Al dissimilar alloy welding joint is obtained.The method can effectively control the composition of the transition layer.The process optimization of the control group was set up,such as the design of the welding joint,the adjustment of the welding parameters,the adjustment of the partial beam amount and the weld root reinforcement welding,The effect of each group on the formation of welding seam was analyzed.By optical microscope and scanning electron microscope to some of the control group(SEM)and accompanying spectrum analyzer(EDS),X ray diffraction(XRD)study of microstructure distribution,elements distribution and the phase composition,the static tensile test and hardness test were carried out to evaluate the performance of different mechanical joints.Aluminum lithium alloy welding is composed of base metal,heat affected zone,fine grain zone,columnar zone and equiaxed zone,in the process of welding joint softening leads to low weld strength.Melt brazing of intermetallic compounds are shaped,serrated and three kinds of cellular growth morphology,growth by partial beam amount and the location of the interface,the rod of intermetallic compounds on the interfacial bonding strength is enhanced,the cellular binding strength of the worst.It can be found from the line scan that the larger the partial beam is,the thinner the interface reaction layer is,and the reaction layer is thinner and thinner from top to bottom.Combined with the linear scanning and the region scan,the results show that the single phase of the rod like and the serrated metal compounds are unstable,so it makes the hypothesis of the inverse defect.After welding process optimization by TiAl3,Ti5Al11,TiAl,Ti3Al in four phases,most of them shaped,serrated and cellular intermetallic compounds is TiAl3,and the root of these organizations are continuous transition layer of Ti5Al11,TiAl and Ti3Al intermetallic compounds.The tensile strength of the welded joint after process optimization can be reached 260MPa.Tensile fracture of weld can be divided into ductile fracture and the brittle fracture,ductile fracture surface dimple and a large number of second phase particles,brittle fracture surface showing cleavage facet.Fracture process is from the lower part of the weld area began to crack the gap,with the extension of the length of the changes in the fracture surface extension of the ultimate ductile fracture.The brittle fracture is mainly composed of TiAl3,which is mainly composed of Al Li alloy.