Interface Morphology And Bonding Properties Of Ti/Al Laminated Material Prepared By Ultrasonic Additive Manufacturing

Titanium/aluminum composites have the characteristics of low density,high specific strength,strong corrosion resistance and plastic deformation ability.They have broad application prospects in aerospace,electronic information and other fields.In this paper,Al1100 and TA1 laminated composites were prepared by ultrasonic additive manufacturing(UAM).The influence of process parameters on the interface morphology of laminated materials was studied.The microstructure evolution of Ti/Al interface was analyzed,the bonding strength of Ti/Al laminated materials was measured and the fracture mechanism was analyzed.The research results have important theoretical significance and application value for broadening the preparation and application field of Ti/Al composites.The interface bonding between Ti and AI of laminated material is perfectly combined with a linear welding density of 100%at the normal pressure of 0.25-0.45 MPa,the consolidation amplitude with Ti layer of 20.0-27.5 μm,the amplitude with Al layer of 20 μm,the travel speed with Ti layer of 15.0-25.0 mm/s and Al layer of 25.0-35.0 mm/s,and preheating temperature of 20-100℃.Due to the great differences in physical properties of Ti and Al materials,when Al layer is added to Ti,the interface is wavy and curved,forming the morphological characteristics named mechanical chimera.When Ti layer is added on Al,the Ti/Al interface is relatively flat.There is mutual diffusion at the interface between Ti and Al of the laminated material without intermetallic compound.The microstructure in the core of Ti layer of the laminated material are equiaxed grains.The rolled grain of Al1100 is characterized by fine fragmentation.Dynamic recovery and recrystallization occurs in the Al layer due to plastic deformation and interlayer heat generation at the Ti/Al interface,and new distortion-free equiaxed grains replace deformed grains in the Al layer during UAM.The number of large angle grain boundaries increases,both the degree of dislocation packing and the angle of local misorientation decreases.After UAM,the micro-hardness of Ti layer is higher than that of TA1 foil strip due to work hardening;The softening occurs in the Al layer,and the micro-hardness after recovery and recrystallization is less than 1100 foil strip.With the increase of normal pressure and amplitude,the peeling strength and peeling work between Ti/Al laminated increase,and the maximum peeling strength is 8.5 N/mm.There are two kinds of stripping fracture morphology and they are Ti/Al interlayer cracking and internal tearing of Al layer.The increase of normal pressure and amplitude changes the fracture morphology from interlayer cracking to internal tearing of Al layer.The area of pure aluminum adhered to the inner surface of Ti layer at the stripping fracture increases.The area of dimple increases,and its size becomes smaller and deeper,the stripping strength between Ti and Al layers is thus improved.During the tensile process,cracks occur between Ti and Al layers,and the normal pressure increases to improve the interfacial bonding performance.The maximum tensile strength in the consolidation direction(RD)and perpendicular to the consolidation direction(TD)are 275.2 MPa and 231.2 MPa respectively.The increase of consolidation amplitude leads to the dislocation accumulation.During the tensile process,Ti layer and Al layer are easy to fracture at the stress concentration,resulting in the decrease of tensile strength.The axial vibration of ultrasonic sonotrode makes the plastic deformation of metal foil belt in TD direction larger than that in RD direction,which causes more dislocation accumulation.Microscopically,it causes the anisotropy of grains in Ti/Al layer,resulting in the tensile strength of laminated material in RD direction higher than that in TD direction.