Laser Shock Peening 50CrVA Alloy To Improve The Mechanical Properties

50CrVA alloy has the characteristics of strong toughness and high strength,and is widely used in the manufacturing of key load-bearing components such as small aircraft landing gears.However,these load-bearing components have been used in harsh environments for a long time,and local wear and damage often occur on the surface of metal materials,which can easily lead to the failure of the entire component.Laser shock peening(LSP)is a promising surface modification technology that can improve the mechanical properties of aerospace components by improving the hardness of materials,refining grains,and introducing beneficial compressive residual stress(CRS)near the surface.In this paper,LSP technology was used to modify the surface of 50 CrVA alloy used for aircraft landing gear loadbearing components.The residual stress and mechanical properties of LSP treated50 CrVA alloy were studied through simulation and experiments.First,the distribution of residual stress field in LSP treated 50 CrVA alloy was analyzed using finite element simulation method,and key process parameters were optimized.Then,based on an experimental system,the effects of LSP on residual stress,microstructure,microhardness,tensile properties,and fracture morphology of50 CrVA samples were studied.Finally,the strengthening mechanism of LSP treated50 CrVA alloy was discussed in depth.The specific research content and results are as follows:Simulation study on LSP strengthening treatment of 50 CrVA alloy.In this study,the three-dimensional finite element model was benchmark tested by studying the convergence of grid size and time step size,and then the dynamic propagation characteristics of laser induced shock waves within the material were predicted using the benchmark finite element model.The effects of key process parameters such as laser energy and laser spot diameter on the residual stress distribution of 50 CrVA alloy were further studied.The simulation results show that adjusting two key process parameters can effectively improve the CRS distribution of metal materials,and the spot diameter has a greater effect on improving the uniformity of residual compressive stress distribution than laser energy.Considering the influence of two key parameters on the residual stress distribution of 50 CrVA alloy,an optimized LSP process parameter combination was obtained.Experimental study on LSP strengthening treatment of 50 CrVA alloy.The residual stress,microstructure,and mechanical properties of 50 CrVA alloy before and after LSP treatment were studied using optimized process parameters.The experimental results indicate that LSP treatment introduces beneficial gradient residual stress on the surface of the material,with an impact depth of approximately400μm.After LSP,there was no change in phase composition,but it weakened the texture strength and refined the grains.Under the action of grain refinement and CRS,the surface microhardness of 50 CrVA alloy is significantly improved,while the ultimate tensile strength and yield strength are also enhanced,while the elongation slightly decreases.The size of the dimples in the fracture morphology becomes small and shallow after LSP treatment,indicating a slight decrease in toughness,which can be attributed to the grain refinement of the surface layer of the metal material caused by LSP treatment.In addition,theoretical analysis reveals that the strengthening mechanisms mainly include grain boundary strengthening,dislocation strengthening,and CRS strengthening.This study verified the feasibility of LSP to improve the mechanical properties of 50 CrVA alloy.