Numerical Simulations On The Coupling Thermal-Mechanical Behaviors Of Metals In Additive Manufacturing

Additive Manufacturing(AM)is commonly known as 3D printing.As one of the core technologies of the third industrial revolution,AM technology is becoming more and more mature with the development of technology and intelligent manufacturing.AM technology is a kind of rapid prototyping techniques to construct structures based on the 3D digital model file and powder materials such as metal and plastic.AM will become the most promising manufacturing technology and will also bring revolutionary change to the equipment manufacturing industry.Electron beam melting(EBM)has emerged as one of the primary metal AM technologies used for many applications in various industries such as mechanical and aerospace engineering due to its high energy and high absorption rate.However,the EBM manufacturing is still under development and the related products usually suffer from poor mechanical properties due to the presence of facture,delamination and void.In this paper,the coupling thermo-mechanical behavior of Ti-6Al-4V metallic alloys in the additive manufacturing process is simulated by using the commercial finite element software ABAQUS.We first establish an improved model by considering the change of material thermal and mechanical properties caused by powder melting with consolidation.The results show that the proposed model can reasonably predict the size of the molten pool as comparing to experimental results.Based on the improved model,the influence of the heat source power and the printing speed on the size of the molten pool is studied,and the influence of the powder thickness and the spacing on the printing quality is also investigated.The results showed that,when the printing speed is low(i.e.,0.2m/s~1m/s),its impact on the molten pool length is negligible,while the width and depth of the molten pool decrease significantly with the increase of the printing speed.With the increase of the heat source power,the size of molten pool gradually decreases.Furthermore,it is found that,when the heat source power is 80 W,the scanning speed is 0.8m/s,the powder's thickness is 30?m and the scanning spacing is 80?m,the printed samples have better quality and the printing process is of high efficiency and utilization.In addition,the residual stress and deformation behavior of the products are studied when the model and environmental temperatures are 20 ? or 730 ?.Simulation results demonstrate that the residual stress and deformation are small when the model and environmental temperatures are both 730?,which indicates that preheating powder bed and ambient temperatures can reduce the residual stress and expansion deformation.Finally,the influences of the powder feeding modes(i.e.,spreading powder and feeding powder)on the quality of products are also studied.