Numerical Simulation And The Growth Behavior Of Diffusion Layer During The Preparation Of Aluminum Diffusion Layer On Steel Surface

The rapid development of modern industry needs higher and higher requirements on the service performance of materials,especially those materials applied in the aerospace,energy industry and other fields,which need to have well high temperature oxidation resistance and corrosion resistance.Because of its good resistance to high-temperature oxidation and corrosion,aluminized layers are widely used in various industrial fields.The most commonly used Fe-Al alloy diffusion layers have excellent performance and low cost.There are many industrial methods used to prepare this diffusion layer.Each method all have their own characteristics and applicable occasion.In this paper,inspired by the alloy layer that appeared at the interface when the materials were connected,using the thermal effect provided by the tungsten inert gas welding and the strong-deformationinduced rapid diffusion effect of the friction stir processing,two new methods for preparing the aluminum infiltration layer were proposed.The temperature field during the two methods and the residual stress field after the preparation are established by finite element analysis.Through thermal calculation and kinetic calculation,the growth processes of the intermetallic compound layer were clarified,and the atomic diffusion behavior at the interface was clarified.The preparation of aluminized layers was carried out by tungsten inert gas welding on the surface of the steel substrate and aluminum / steel lap friction stir processing.Based on the secondary development function of Abaqus,by means of finite element analysis,the temperature fields of the two preparation methods were calculated and analyzed,and the temperature fields were verified by the experimental results of published literature.The temperature field results showed that the arc as a typical transient heating process,the temperature rised rapidly.During the preparation process,the peak temperature was maintained at 870 ?.As a solid-phase treatment method,friction stir processing requires a period to heat up the process.The peak temperature during the stabilization phase was maintained at about 500 ° C.The comparison of the thermal cycle curves inside the diffusion layer showed that the uniformity of the diffusion layer prepared by arc cladding is better than that of the aluminum/steel friction stir processing.The calculation results of the residual stress field showed that the maximum longitudinal residual tensile stress on the surface of the steel substrate reached 513 MPa after the arc cladding.After the friction stir processing,the maximum longitudinal residual tensile stress on the surface of the steel substrate was 260 MPa,a decrease of about 49.3%.In both preparation methods,the residual stress of the aluminum diffusion layer does not exceed 30 MPa.The effect of different process parameters on the residual stress after the preparation was studied.The results showed that by changing the preparation process parameters,the residual stress peak,as well as the compressive stress and tensile stress distribution can be changed.Thermo calculations were used to analyze and predict the phase composition of the diffusion layer.Through the calculation and comparison of the diffusion coefficients,it was found that there was a fast diffusion behavior of atoms in the preparation process of the friction stir processing.The diffusion layer growth processes in the preparation process of two methods were clarified.In the preparation of arc cladding: liquid aluminum spread and wet on the surface of the steel substrate,causing physical and chemical adsorption,aluminum atoms diffused into the steel substrate,and intermetallic compound crystal nucleuses were generated at the interface under thermodynamic conditions,under the continuous action of diffusion,Intermetallic compounds grew and eventually formed a layered structure.In the preparation of friction stir processing: the severe plastic deformation generated by the stirring head causesd the material at the aluminum-steel interface to be fully mixed,under the action of thermal coupling,the grains at the interface were refined,and much crystal defects were induced,the diffusion process was transformed into the diffusion of the pipeline,crystal nucleuses were generated at the interface,under the continuous effect of diffusion,the intermetallic compound grew up and eventually formed a layer structure.