Technology And Microstructure-properties Of Ti And Al Dissimilar Materials For Joining Structure Using CMT Arc Additive Manufacturing

The Ti/Al dissimilar materials component was widely used in aerospace,transportation and weapons industries.Thereby,according to the engineering application requirements,it had the great theoretical and practical application significance to study the CMT arc additive manufacturing of Ti/Al dissimilar materials connected structural component.Firstly,this research performed the experiment of dissimilar materials structure component fabricated by CMT arc additive manufacturing using Ti-6Al-4V and Al-5Si wires.It was found that the reaction layer of Ti/Al dissimilar component included the Ti₇Al₅Si₁₂ continuous reaction layer and Ti(Al_1-xSi_x)₃ discontinuous reaction layer.Ti₇Al₅Si₁₂ and Ti(Al_1-xSi_x)₃were found at the fracture surface of the component.To avoid the formation of the intermatic compound with Si element,the Al wire with lower Si content should be selected as far as possible during selecting Al wire.Secondly,the Ti/Al dissimilar materials component fabricated by using the Ti-6Al-4V and Al-6.25Cu wires was performed.The effect of deposition order on component formation and reaction layer was studied.It was discovered that the Ti alloy was deposited first,the formation of Ti and Al alloys was fine,a fusion brazing joint was formed,and TiAl₃ was formed in the reaction layer between the Ti and Al alloys.When the Al alloy was deposited first,there were voids in the interface between Ti and Al alloys.Ti alloy near the interface was rough.A fusion joint was formed,which led to the formation of TiAl_3,TiAl and Ti₃Al.Depositing the Ti alloy first was found to be more suitable for CMT arc additive manufacturing process of Ti/Al dissimilar alloys.Thirdly,the effect of CMT mode on reaction layer by changing the mode of Al alloy deposition process was studied.The researches showed that at the same wire feed speed,the reaction layer consisted of TiAl₃ and the thickness was?10?m using the DC-CMT(Direct current CMT,DC-CMT)and VP-CMT(Variable polarity CMT,VP-CMT)modes.The reaction layer consistsed of TiAl₃,TiAl and Ti₃Al,and the thickness is?2 mm using the CMT+P(CMT plus pulse,CMT+P)mode.The reaction layer consisted of TiAl₃ and the thickness is?1 mm using the VP-CMT+P(Variable polarity CMT plus pulse,VP-CMT+P)mode.Studies showed that using the DC-CMT and VP-CMT moeds for Al alloy were more suitable for CMT arc additive manufacturing process.Last,the effect of Al alloy deposition layer on the reaction layer.It was found that the TiAl₃ phase in the long strip in the reaction layer grew from perpendicular to the surface of Ti alloy to random growth with the increase of the Al deposition layer number using DC-CMT mode.The matrix of the reaction layer was TiAl,and the acicular Ti₃Al was formed using CMT+P mode.TiAl₃ with the strip and continuous lamellar shape was formed with the increase of deposition layer of Al alloy.