Study On Process Method And Microstructure Properties Of Ti/Al/Mg Laminated Composites Prepared By Differential Temperature Rolling

Metal layered composite materials can greatly improve the strength,thermal expansion,impact toughness,wear resistance,electrical properties and other properties of a single metal material.It has been widely used in aviation,aerospace,defense,electronics,chemical equipment and other fields,but rolling bonding of heterogeneous metal materials with large differences in mechanical and physical properties still faces urgent problems such as unhomogeneous deformation,low bonding strength and sheet fracture failure.The pure titanium(TA1),aluminum alloy(AA6061)and magnesium alloy(AZ31B)are taken as the research objects in this paper.A method of differential temperature rolling(DTR)based on homogeneous deformation is proposed,and the preparation process from the Ti/Al,Ti/Mg double-layer composite plates to the Ti/Al/Mg,Ti/Mg/Al three-layer composite plates are gradually realized by optimizing and designing the DTR method and process.The effects of the DTR process on the deformation coordination and microstructure properties of the composite plates are studied.Furthermore,the bonding mechanism of the DTR laminated composites is revealed.Both of the Ti/Al and Ti/Mg laminated composites are prepared by only heating the titanium layer,and the influence of the reduction ratio and the heating temperature on the thickness ratio distribution,shear strength and bonding interface of the laminated composites is studied.The results show that as the temperature of the titanium layer and the rolling reduction increase,the difference in the deformation between the two layers of the laminated composites gradually decreases,indicating that the deformation of the composite plates tends to be homogeneous.The bonding strength of the Ti/Al composite plates increases first and then decreases with the increasing temperature of the titanium layer.And the bonding strength of the two types of composite plates increases with the increase of the rolling reduction.In addition,an oxide layer is formed on the surface of the titanium plate during the heating process.However,the brittle titanium oxide layer and the titanium matrix rupture in sequence to produce micro cracks,and the metal matrix on the other side squeezes into the crack to contact the fresh titanium metal.Under the action of pressure and high temperature,the elements diffuse with each other so as to achieve a combination mechanism of crack mechanical engagement and metallurgy.However,the DTR method that only heats the titanium plate oxidizes the surface of the titanium plate.The uneven deformation of the brittle oxide layer and the metal matrix causes a large number of cracks at the interface,which negatively affects the tensile and bending properties of the composite plates.Therefore,the DTR method via the induction gradient heating is innovated to prepare Ti/Al and Ti/Mg composite plates.Meanwhile,the whole process is in an argon atmosphere to avoid surface oxidation in the plates.The effect of reduction on the mechanical properties and the microstructure of the composite plates is studied.The results show that the clean and non-oxidized interface significantly improves the bonding strength of the composite plates.In particular,the bonding strength is increased by about 3-5 times at a low reduction.Under large reduction ratio,both sides of the shear section present a large number of ductile fracture characteristics,and the interface has a dual bonding mechanism with mechanical engagement and metallurgy.The strong bonding interface can improve the ability of the laminated composites to resist interfacial delamination and bending deformation,and the composite plates obtain satisfactory comprehensive mechanical properties.On the basis of the research for double-layer composite plates,a method of rolling Ti/Al/Mg and Ti/Mg/Al three-layer composite plates by transverse electromagnetic induction heating under protective atmosphere is designed.The composite plates are subjected to DTR experiments with different reduction ratios,and the shear strength,fracture morphology and three-dimensional profile of the three-layer composite plates are studied.Moreover,the effect of the comparison for the lamination sequence on the bending performance of the composite plates is studied.The results show that the dual interfaces of the Ti/Al/Mg composite plates reach a high bonding strength at a large reduction.The Ti/Al and Ti/Mg composite interfaces in the three-layer composite plates deform more severely as the reduction increases.During the evolution from brittle to ductile fracture mode,the height difference of three-dimensional profile for the fracture becomes larger and the roughness of the fracture increases.The Ti/Al/Mg composite plates realize the coordinated deformation of each metal layer,while the deformation of the Ti/Mg/Al composite plates is concentrated on the magnesium metal,indicating that the deformation is uncoordinated.At the same time,the Ti/Al/Mg composite plates achieve a good bending deformation ability.Comparing the temperature difference distribution under induction heating,the coordinated deformability,bonding performance and bending performance of the composite plates after rolling,It is determined that the order of the TiAl-Mg billet assembly with aluminum as the intermediate layer is a reasonable process to realize the high-performance for three-layer composite plates under DTR process.