Research On The Interface Structure Evolution And Control Mechanism Of Al/steel In Arc Additive Manufacturing Under Magnetic Field

With the advantages of light weight,high strength,flexible forming mode and low cost,Al/steel arc weld additive manufacturing components have wide application prospects in the fields of vehicles,aerospace,ships and so on.However,the connection strength of the Al/steel interface is too low,which is the weak area of the whole materialincreasing member.The magnetic field can improve the interface structure and increase the mechanical properties of the joint.The thermal process of additive manufacturing is a temperature change process accompanied by the arc additive manufacturing method,which can have a certain influence on the microstructure and properties of the material increasing component.In this paper,the magnetic field is introduced into the Al/steel arc weld increasing manufacturing process,the evolution behavior of the Al/steel interface structure under the additive manufacturing thermal process is studied,and the control mechanism of magnetic field and additive manufacturing thermal process on the Al/steel interface structure is described.Firstly,the effects of excitation current and magnetic field frequency on the microstructure and mechanical properties of Al/steel interface are studied,and the magnetic field parameters controlled by the initial interface of Al/steel are determined.The magnetic field can reduce the thickness of interface intermetallic compound layer and reduce the formation of?Al,Si?₁₃Fe₄ compound at the interface by reducing the peak temperature during welding,shortening the high temperature residence time,accelerating the flow behavior of molten pool and so on.When the excitation current is 2A and the magnetic field frequency is 0Hz,a compound layer with lower thickness and only one phase of Al₈Fe₂Si can be formed at the Al/steel interface,and the mechanical properties of the Al/steel joint can be increased by 43.2%.It was selected as the magnetic field control parameter of Al/steel arc weld additive manufacturing.Then,the effects of thermal process on Al/steel interface structure under single layer multi-channel and single channel multi-layer material adding manufacturing forms are studied,and the evolution behavior of interface structure with the increase of the number of addition manufacturing at different temperature of addition manufacturing is obtained.The overall evolution of the interface structure under the action of the additive manufacturing thermal process is the formation of?Al,Si?₁₃?Fe,Cr?₄ compound between the initial compound layer and the steel substrate.The growth of the?Al,Si?₁₃?Fe,Cr?₄ will experience rod and lamellar morphology with the increase of the number of addition manufacturing.The increase of addition manufacturing temperature will increase the number of intermetallic compounds in aluminum weld,accelerate the evolution of interface structure,and even form Fe2Al5 compound between?Al,Si?₁₃?Fe,Cr?₄ compound and steel substrate.Finally,the evolution model of Al/steel interface structure under the additive manufacturing thermal process is established,and the control mechanism of magnetic field and thermal process on the interface structure of Al/steel is discussed.Under the action of additive manufacturing thermal effect,the?Al,Si?₁₃?Fe,Cr?₄ compound with rod morphology formed by interfacial reaction can inhibit the crack propagation in the Al₈Fe₂Si compound layer.Under the action of additive manufacturing thermal accumulation,the?Al,Si?₁₃?Fe,Cr?₄ compound with lamellar morphology grown by diffusion behavior will be the crack source in shear test.The formation of Fe2Al5 compounds under high frequency thermal shock will lead to a sharp decrease in the interfacial strength.The magnetic field can not only improve the initial interface structure,but also decrease the peak temperature and high temperature residence time of the subsequent additive manufacturing thermal process.Reasonable adjustment of the temperature of addition manufacturing can cause proper thermal shock and form the interface structure of the compound in the form of mosaics.