Optimization Of Welding Parameters During Ti-TA2/5A06Al Dissimilar Double-sided Cold Arc MIG Welding

Due to the serious mismatch in physical and chemical properties,the brittle intermetallic compounds(IMCs)are appeared in traditional fusion welding of the titanium and the aluminum dissimilar welding,which greatly reduced the mechanical properties of joints.It is considered to have poor fusion weldability between the titanium and the aluminum.The weld appearances and properties of Ti/Al dissimilar parent metals were obviously improved with welding-brazing.However,the single sided welding-brazing has always been oppressed by the great structural differences of brittle intermetallic compounds(IMCs)along the Ti/Al interfacial.In this study,SAl 5183 wire was used to the welding of the Ti-TA2/5A06Al dissimilar joint by double-sided cold arc MIG welding-brazing method.The influence of different welding parameters on the microstructure and properties of titanium/aluminum dissimilar joint was studied.Optimization ranges of welding parameters were obtained through comparative analysis.The effects of front welding heat inputs,bevel angles and wire offsets on the weld appearance,cross section morphology,microstructure and tensile strength of the joints were studied.The optimized range of welding heat input was E=0.94 k J/cm?1.24 k J/cm,bevel angle was?=35°?45°;wire offset was d=-1.0mm to?1.0mm.The tensile strength of the joint exceeded 300 MPa.When the welding heat input was low,the joint was poorly formed and the interface metallurgical bonding was insufficient.The tensile strength of the joint was low.When the heat input was moderate,the joint was well formed.The interface reaction was sufficient and the tensile strength was the highest.When the heat input was too large,the burn through defect occurred and the titanium parent metal partially melted.The tensile strength of the joint decreased.When the bevel angle was small,the weld appearance was well formed.The great difference of the interface microstructure was appeared and the tensile strength of the joint was low.When the bevel angle was moderate,the interface metallurgical bonding was sufficient.The tensile strength of the joint was high.When the bevel angle was too large,the interface metallurgical bonding was insufficient and the tensile strength of the joint decreased.When the partial titanium wire was too much,the weld appearance was well formed,the titanium parent material partly melts,the joint tensile strength was low.As the wire offset towards the aluminum parent metal,the weld surface was well formed,and sufficient metallurgical bonding occurred near the interface.The tensile strength of the joint was high.When the wire offset towards aluminum too much,burn through defects were occurred and the tensile strength of the joint was reduced.In the Ti/Al dissimilar joint obtained by optimizing the welding process,in the upper part of the Ti/Al interface,a double-layer structure of the Ti₃Al layer and serrated Ti Al₃ layer were formed between the titanium and the weld to realized the welding-brazing.A single Ti Al₃ layer was formed between the titanium and the weld at other location.During the tensile text,the joints fractured near the Ti/Al interface,the fractured surface exhibited a mixed brittle-ductile fracture mechanism.