Research On The Capacitor Discharge Joining Of Titanium TA2 And Stainless Steel 0Cr18Ni9 Sheets

The titaniurm/steel composite structure combines the high corrosion resistance of titanium and the excellent mechanical properties of steel,and is widely used in ships,petrochemical industry and electric power industry.Due to the difference in physical and chemical properties of titanium and steel,a large number of brittle intermetallic compounds are easily formed in the welding zone,which weakens the mechanical properties of the joint.In this paper,the rapid solidification connection of TA2 and 0Cr18Ni9 sheets was implemented by the capacitor discharge joining process,which was designed to suppress the brittle intermetallic compounds and improve the joint mechanical properties.By adding Ti-Fe-Ni-Cr-Co,Ti-Fe-Ni-Cr-Cu,Ti-Fe-Ni-Cr-Co-V,Ti-Fe-Ni-Cr-Co-Cu interlayers,the high entropy properties and its influence on the joint structure and properties were studied.The results show that:The joint of TA2/0Cr18Ni9 sheet by the capacitor discharge joining,The whole cross section morphology of the nugget is jujube.The capacitor discharge joining can realize the effective joint of TA2/0Cr18Ni9 sheet.The whole cross section morphology of the nugget is jujube,with a length of 2000μm and a height of 300μm.The nuggets in titanium side is mainly fine columnar crystal and other axial crystal structures,with several cracks which the longest up to 100μm.The TiFe compound layer was formed on the near titanium side of the interface,with the thickness of 30μm.There are opposite growing structures on bonding interface with many vertical cracks,which are mainly TiFe and TiFe2 brittle intermetallic compounds with a thickness of 5-8 μm.The nuggets of the steel side is the columnar crystal and other axial crystals,and the width of fusion zone is about 12～18 μm.Under the CDW condition of the electrode pressure 45N,the charging voltage 1050V,and the charging capacitance 500μF,the mean shear strength of joints was respectively 178 MPa.Based on nugget metal high entropy alloying technology,Ti20Fe25Ni25Cr20Co10,Ti20Fe25-Ni25Cr10Cu20,Ti20Fe25Ni25Cr10Co10V10 and Ti20Fe25Ni25Cr10Co15Cu5 are designed according toaccording to solid solution formation criterion,thermodynamics first principles and density functional theory,which plastic toughness are well,further to convert Fe2Ni51Cr23Co24,Ni46Cr3Cu51,Fe2Ni51Cr4-Co25V18 and Fe1N148Cr3Co34Cu131 interlayer alloys.The mechanical properties of joints were improved by adding interlayer based on the high entropy nuggets,because brittle intermetallic compounds being reduced and solid solution generating.TiFe,TiFe2 and other brittle intermetallic layers generate near the titanium side,which have a thickness of 10～15 μm,and the width of much less than the non-middle layer.Under the CDW condition of the electrode pressure 45N,the charging voltage 1050V,and the charging capacitance 500μF,the joints have good shear strength.When adding Fe2Ni51Cr23Co24、Fe2Ni51Cr4Co25V18、Fe1Ni4sCr3Co34Cu13 interlayers,the microstructure changes of the joints were:Ti(s,s)→(α-Ti+TiFe)→(FCC+BCC)(s,s)→γFe(s,s)along perpendicular of binding interface.The formation of simple solid solution layers with good plasticity,which has good plasticity,effective release joint stress and decrease joint cracks.The mean shear strength of joints was respectively 294,243 and 293 MPa.When adding the middle layers of Fe2Ni51Cr23Co24 and Fe2N151Cr4Co25V18,the content of the simple solid solution layer in the nuggets was similar to that of the design of the nuggets:Ti2oFe25Ni25Cr2oCo10 and Ti2oFe25Ni25Cr10Co10V10.The content of the simple solid solution elements by adding the middle layer of Fe1N148Cr3Co34Cu13 was significantly different from the Fe1Ni48Cr3Co34Cu13 nugget.The formation of simple solid solution in nuggets can effectively inhibit the layers of brittle intermetallic compounds in titanium/steel CDW and improve the welding quality based on the high entropy effect.Solid solutions with different ingredients affect joint quality,Increasing V element content in the joint,can improve the solid solution formed tendency in titanium/steel joint,and improve BCC phase volume fraction,which result in solid solution layer brittleness increasing,the number of crack increasing and the quality of the joint decreasing.