Research On Thermal-mechanical Chatacteristics Of Aluminum Alloy By Arc Additive Manufacturing Process

Tungsten inert gas(TIG)additive manufacturing is an advanced technology based on local and centralized heating of metal wire by high temperature arc and forming by layer by layer surfacing.It has gradually become an efficient method for manufacturing large-size thin-walled parts and repairing product functions in aviation,automobile manufacturing and military industries.However,due to the interaction among arc,workpiece and substrate in the additive process,the complex thermal-mechanical characteristics are easy to form a large temperature gradient,resulting in microstructure distortion and forming defects,which ultimately affect the quality of the parts and restrict the further development of the technology.The TIG process is used to carry out 5356 aluminum alloy forming experiments.Based on the method of combining numerical simulation and experiment,the evolution law of the thermal-mechanical in the additive manufacturing process and the influence of different processes on the thermal-mechanical characteristics are studied,and performance tests of the formed parts under the optimization scheme are carried out.According to the principle and characteristics of TIG additive manufacturing,the finite element model based on ABAQUS is established.The application program of "Model Change Add and Remove" method is compiled with Python language.Through the secondary development of ABAQUS,the subroutine of double ellipsoid heat source is compiled,and the finite element simulation of the forming process is realized.On this basis,temperature characteristics and stress distribution laws of multi-layer straight body forming parts are analyzed.The influence mechanism of substrate preheating,arc direction and cooling time interlayer on thermal-mechanical distribution and forming quality is studied,and the process optimization method is established to effectively control and improve the non-uniform thermal-mechanical distribution in the forming process;The simulation of multi-layer closure part with optimized process parameters is carried out,and the results show that the thermal distribution uniformity of multi-layer closure is good and the residual stress is small.The experimental platform of TIG additive forming is established,and the temperature measurement system is designed by ourselves.The actual temperature and residual stress in the forming process are obtained by combining thermo-couple temperature measurement and X-Ray diffraction(XRD)non-destructive measurement.Through comparison and analysis of the experimental results and finite element simulation results,the reliability of the finite element model and the correctness of the simulation results are verified.The impact tests of the parts formed with optimized process parameters are carried out,and the fracture mechanism in different directions and positions is analyzed.The results show that the fracture form of the samples is ductile fracture,and the toughness values in different directions and positions are approximately equal,and the overall plasticity of the aluminum alloy parts is better.The research results provide theoretical basis and data support for the force prediction and quality improvement of aluminum alloy additive parts in engineering practice.