Research On Current Assisted Ultrasonic Additive Manufacturing Process Of Ti/Al Laminated Composites

Ultrasonic additive manufacturing(UAM),as a new solid-state bonding technology,is widely used in the preparation of dissimilar metal composites,which provides a new scheme for the additive manufacturing of titanium/aluminum.Due to the high hardness and poor plasticity of titanium,the existing process often improves the material consolidation ability by increasing the preheating temperature of the substrate,and there are also some problems to be solved.Based on the ultrasonic additive manufacturing of Ti/Al Laminated Composites,a high-power ultrasonic additive manufacturing system was designed by theoretical calculation and finite element simulation.The effects of key parameters such as consolidation pressure,consolidation velocity and consolidation amplitude on the interface morphology,microstructure and mechanical properties were studied.The interface morphology and the formation mechanism of intermetallic compound layer were also studied.In addition,the current assisted preheating method was introduced to preheat the titanium foil,and the effect of current on the process of titanium foil addition was studied.The results show that the resonant frequency of ultrasonic additive system is20280 Hz and the amplitude is 28.691 ?m.It basically meets the design requirements,and the trial production system can realize the effective consolidation of titanium and aluminum,which meets the actual engineering needs,and proves the rationality of the design scheme.The results show that the surface texture of the consolidated sample is uniform,and there are some defects such as viscosity loss and cracks on the surface under high parameters;Due to the large plastic difference between the two metals,the interface of Ti/Al is straighter than that of Al/Ti,and the thickness of diffusion layer is reduced.Due to the difference of interface transverse stress level,insufficient diffusion and high frequency shear vibration of ultrasonic consolidation,the intermetallic compound layer is not uniform and continuous.With the increase of consolidation amplitude,pressure,preheating temperature and the decrease of consolidation speed,the degree of interfacial plastic deformation and the thickness of diffusion layer increase significantly.However,too high consolidation pressure hinders the transmission of ultrasonic energy and opposes the adverse effects of interfacial deformation and atomic diffusion.The current assisted mode can obtain significant temperature rise in a short time,However,the increase of current will weaken the interface fluctuation and atomic diffusion.The results show that the thickness and continuity of the interface compound are significantly improved by heat treatment,and 3.5% particles are formed at the Al/Ti interface and Ti/Al interface,respectively 6 ?m and 3 ?m compound layer,the current assisted effect is more obvious,up to 5 ?m and 4 ?m? The results show that the mechanical properties of the samples decrease(? 5%)when heated alone or assisted by electric current,and the maximum strength of 231.7 MPa is obtained in the RD direction under the combined action of electric current and thermal assistance,which is attributed to the increase of vacancy concentration and dislocation density in the titanium metal under the current assistance,which promotes the diffusion of interface elements.The rolling effect of indenter leads to the anisotropy of mechanical properties,which is aggravated by current and heat treatment,and the maximum difference can reach 35 MPa;The main feature of tensile fracture is dimple,acco MPanied by necking,and ductile fracture is dominant;The results show that heat treatment can significantly improve the peel strength,and the current assistance has a negative effect on the peel strength.The combination of current and heat treatment can significantly improve the interfacial bonding stability and peel work.