Simulation Investigation Of Laser-melt Injection Of Sic-316l Hybrid Particles On AZ31B Magnesium Alloy Surface

Magnesium alloy as a non-ferrous metal material is widely used, however, poor wearresistance and corrosion resistance of magnesium alloy hinder the further development.Laser-melt injection of SiC-316L hybrid particles on AZ31B magnesium alloy surface, canimprove the wear resistance and corrosion resistance of magnesium alloy surface. UsingAnsys software to simulate the temperature field, stress field of laser-melt injection process.And using Fluent software to simulated the trajectories and distribution of hybrid particles inthe molten-pool under different process parameters. Come to conclusions as follow:(1)Through the matrix temperature field analysis, with the increase of laser power, length,width and depth of molten pool all increases. Exist time of molten pool increases as well.When the laser power is2500W, exist time of molten pool is0.28s. If scanning speed increase,width and depth of molten pool decreases, but its length increases. Compare the differenttemperature fields of matrix under different laser powers and scanning speeds, take exist timeof molten pool, size of molten-pool, matrix evaporation degree three aspects intoconsideration, the most suitable parameters for laser melt injection is laser power P=2500W,scanning speed V=7mm/s. Although laser power and scanning speed increases at a same rate,the temperature of molten pool center is still raising. Obviously, the influence of laser powerto temperature field is greater than scanning speed do.(2)Study the forming theory of the matrix stress field, speculate the stress fielddistribution of the matrix surface. The simulation result is consistent with the speculation.When the temperature of molten pool persist increasing, the matrix should stand tensile stress,caused by tensile plastic deformation; matrix around the molten-pool expansion undercompressive stress firstly, compressive plastic deformation occurs, as the laser evacuate,matrix begin to cooling solidification, again by the tensile stress, tensile plastic deformation.Analyze of the thermal stress changes of the center spot on matrix surface. This point has apreheating temperature before laser arrive there, higher temperature produces compressivestress; and liquid metal produces flow tensile stress; after laser evacuate, which begin tocooling solidification, tensile stress is produced. Because of the non-uniform temperature, sizeof stress have difference. so the biggest stress direct in Y direction, X direction second, Zdirection minimum. Analyze the influence of the stress field distribution on the matrix surfaceby changing the parameters of the laser-melt injection. The result showed that increase laserpower or decrease scanning speed will lead to smaller matrix surface thermal stress. It isbecause the higher laser power or smaller the scanning speed, the laser energy density on thesurface will increase, resulting in larger temperature gradient, so the thermal stress on thesurface of the matrix showed a trend of increase. (3)Compare the SiC–316L hybrid particles trajectory in molten pool of differentinjection angle, you can see that when the injection angle is20°to30°, particle trajectorybehavior more gentle, more easier to rise to the surface of the molten pool; when injectionangle is60°to70°, particle trajectory is steep, sink more closer to the bottom of the pool.When angle is40°to50°, the injected particles can better uniform distribution in the moltenpool, more satisfy the purpose of the laser melt injection, and be in a conformity with theexperimental literature. In order to find out the influence of injection position，injectparticles with velocity V=3.28m/s and injection angle is40°, the trajectories concluded thatparticles injected from the middle and on the left side are much easier to reach the bottom ofthe pool. Particle trajectories mostly have turning point, this is because of the Stokes force andspeed in different direction, and various parts of the molten pool and the liquid flow viscositytemperature different reasons. The greater initial velocity, the distribution of the particles ismuch closer to the bottom of the pool. Simulate the distribution of different particle diameters.Gravity grow faster than Stokes force, so larger diameter, longer displacement in Y direction.With the increase of laser power, the main distribution area of particles is much closer to thebottom of the molten pool; simulate the distribution of particles under different under-coolingdegree, results show that, the greater under-cooling degree, the distribution of particles iscloser to the surface of molten pool. In the process of laser melt injection choosesuper-cooling degree for100to150. Simulations show that the greater scanning speed, theless depth of distribution in molten pool. Preheating on matrix before laser-melt has greatinfluence in inject particles. The higher preheating temperature, the particles are easier toinject into molten pool.