Research On Temperature Field Stress Field Of GH4169 Superalloy Made By Laser Additive Manufacturing

Laser additive manufacturing technology is an advanced manufacturing technology,which processes 3D models into solid parts based on the principle of layered manufacturing.At present,this technology has been widely used in aerospace,automotive manufacturing,biological and medical fields.However,due to the extremely high temperature of the molten pool in the process of laser additive manufacturing,it is difficult to measure the stress and strain.Therefore,exploring the forming mechanism of laser additive manufacturing and analyzing the temperature field and stress field distribution have guiding significance for the forming quality of laser additive manufacturing superalloy parts.ANSYS numerical simulation software is used to establish a cuboid finite element model.The heat source is approximated as Gaussian heat source.Birth-death element and APDL(ANSYS Parameter Design Language)parametric language command flow considering latent heat of phase change and material nonlinear problems.The temperature field and stress field during laser additive manufacturing process has been simulated.By analyzing temperature filed of four commonly used scanning methods in laser additive manufacturing process,properties like temperature field distribution of different scanning methods,scan line change to transfer and temperature changes trend with entire time course have been studied.The change of temperature gradient in Y and Z directions was analyzed.The stress field variation law is obtained by using the thermal-mechanical coupling method.The thermal stress of the four scanning methods,residual stress after cooling to room temperature,the plastic strain and deformation of the formed part were analyzed.It is found that the thermal stress decreases with the cladding process.When the formed part is cooled to room temperature,the residual stress is different and mainly concentrated at the bottom edge of the cuboid and plastic strain in the X direction(length direction)is the main cause of cracks in the formed part.Among four scanning methods,Path4(scanning method: each layer rotates clockwise by 67°)has the smallest heat-affected zone,larger low-temperature region,and the smallest thermal stress,residual stress,and deformation.So,Path4 is determined as the most suitable scanning method for laser additive manufacturing test.The laser additive manufacturing experiment of GH4169 was carried out with the determined scanning method,the cuboid parts with good density has been produced.By comparing the simulated results of residual stress and X-direction plastic strain of Path4 with the experimental results,which can be concluded that the residual stress is mainly distributed at both ends and center of the parts,and the residual stress is more concentrated at both ends.However,defects such as dislocations and cracks parallel to the scanning direction were found by observing microstructure,which correspond to the results of theoretical analysis and numerical simulation.Therefore,the finite element simulation is more successful in predicting defects.