Numerical Simulation Of Temperature Field And Stress Field During Laser Cladding Of Aluminium Alloy

In this paper,ANSYS software is used to simulate the temperature field in the laser cladding process of aluminum alloy,and the influence of different laser power and scanning speed on the thermal behavior in the laser cladding process is studied.An improved three-dimensional finite element model is proposed to study the thermal behavior and microstructure evolution of laser cladding alsi10mg alloy.Through experiments and theoretical calculation,the different material properties of alsi10mg powder and alsi10mg alloy are distinguished,which provides more reliable material parameters for numerical simulation.At the same time,in order to study the melting and solidification behavior in the process of cladding,a temperature selection judgment mechanism was established to simulate the transformation of alsi10mg from powder state to melting state and then to alloy state.In addition,in order to further simulate the influence of powder particles and interstices on the temperature distribution,a simplified exponential decay model is used to modify the heat source.At the same time,considering the different thermal physical properties and laser absorptivity of the materials on both sides of the remelting zone,the multi-channel laser cladding simulation is carried out with the composite asymmetric heat source.By simulating the evolution of temperature distribution in the cladding process,the improved finite element model can be used to predict the geometry of cladding layer?ignoring the influence of molten pool flow?and the temperature change process.The results of the model are in good agreement with the experimental results.In this paper,the transient and residual stresses and thermal deformation of laser cladding are studied by means of indirect thermal mechanical coupling.It is found that the maximum stress value is generated along the contact line at the junction of the molten pool and the matrix,and this position is mainly subject to the compressive stress.The higher the temperature is near the molten pool,the greater the temperature gradient is easily generated relative to the materials in the low temperature zone nearby,which makes the compressive stress reach about 172Mpa,while the compressive stress behind the molten pool decreases rapidly with the distance from the molten pool During the cooling process,it gradually decays to about 16MPa.With the increase of scanning speed,the maximum instantaneous stress in the sample increases gradually.When the molten pool solidifies,the cladding begins to cool and contract.Because the cladding surface is not constrained by external force,only a small tensile stress is produced during the cooling and shrinking process.The surface of the cladding layer is prone to defects such as pores,so the residual stress on the surface of the cladding layer may lead to the appearance of surface cracks.The cladding layer has a small thermal expansion?0.06mm?and a slight warping of the substrate.According to the simulation results of reading temperature field on the molten pool boundary,the effects of temperature gradient?G?,solidification growth rate?R?,G×R and G/R on the microstructure and size of the cladding layer under different laser scanning parameters were studied.Combined with the experimental results,the higher the G×R value,the higher the microhardness of the cladding layer.When the laser scanning speed is 0.01m/s and the laser power is 800W,the value of G×R is 1.7×10³?5.3×10³?/s.at this time,the forming quality of the cladding layer is the best and the average microhardness is the highest(96.6HV_0.05).Compared with the experimental results under different process parameters,the higher the laser energy density is,the less the defects such as porosity and spheroidization are.