Molecular Dynamics Simulation Of Melting Behavior In 3D Printing Repair Of Automotive Aluminum Alloy Parts

As a representative of lightweight alloys,aluminum alloys are widely used in many fields such as automobiles,aerospace,and ships.Automotive aluminum alloys are mostly die-casting and are not easy to repair.It is difficult to continue to use them once they are damaged.As a new manufacturing technology,3D printing technology has a very important position not only in the manufacturing field,but also in the field of parts repair.At present,the research on 3D printing technology is quite mature,especially on the metal 3D printing process.But in the field of 3D printing repair,especially the research on the repair process of metal parts is not much.The main reason is that 3D printing repair has strict requirements on materials,and experimental research can only obtain the changes of relevant tissues and mechanical properties before and after repair.It is difficult to capture the melting behavior of metal powder during the repair process,and the melting behavior of metal powder has an important influence on the repair effect of 3D printing.Therefore,the research on the melting behavior of metal powder particles in 3D printing repair is of great significance.This article uses molecular dynamics simulation methods,taking Al-Si-Mg alloy as the research object,by simulating the melting behavior of metal powders under the action of high-energy lasers and the tensile properties after solidification,the powder particle size and uniformity,hole defects and multi-particles are studied.The effect of arrangement on the melting behavior and the changes in mechanical properties before and after 3D printing to repair the damaged block.First,a two-particle melting model of Al-Si-Mg was established to simulate the melting behavior between two particles during the heating process.The effects of particle size and particle uniformity on the melting behavior were studied in combination with the crystal structure ratio,radial distribution function,radius of rotation,and displacement vector.The effect of powder particles with different size and number of hole defects on the melting behavior was also studied.It is concluded that the larger the particles,the longer the melting time,the particles with inhomogeneity will shorten the melting time to a certain extent,the effects of hole defects on the melting behavior are not significant,and the atoms on the inner wall of the holes migrate to the outside of the particles due to surface tension.Then,a multi-particle Al-Si-Mg melting model was established to simulate the effects of four different arrangements between particles on the melting behavior,and the tensile and compression properties of multi-particle models with different sizes after melting and solidification were studied.It is found that the arrangement mode has no obvious effect on the melting time,but it will affect the rate of crystal structure transition in the particles.The larger the particles,the higher the elastic modulus and tensile strength in tensile properties.Finally,a damaged block model was established and 3D printed repair was performed to simulate the tensile properties of the block before and after 3D printing repair.The tensile strength and peak strain after repair are improved to a certain extent compared with those before repair.