Investigation On Electrochemical Corrosion Resistance And Tensile Properties Of 6061-T6 Aluminum Alloy Subjected To Multi-layer Laser Shock Peening

Aluminum alloy has the characteristics of low density,high specific strength and strong plasticity.It is widely used in high-end manufacturing industries such as aviation,automobile manufacturing and offshore engineering.It has various mechanical properties that have a major impact on the service life of large-scale sophisticated equipment.Laser shock peening is a new type of surface enhancing technology,it can effectively improve the microstructure and surface integrity of materials,inhibit the initiation and propagation of cracks on the surface of materials,and improve the mechanical properties of materials.It is often used for surface treatment of vital components.However,the effect of multi-layer laser shock peening on the electrochemical corrosion resistance and tensile property of aluminum alloys has not been systematically researched.In this paper,6061-T6 aluminum alloy was used as the research object and a laser shock peening system with multi-parameter integrated control was constructed,numerical simulation and experimental analysis methods were applied to explore the electrochemical corrosion resistance and tensile property of multi-layer laser impacted aluminum alloys.The main research works are as follows:(1)Construct a laser shock peening system with multi-parameter integrated control.when the experiment was performed on the 5-axis working platform in school laser institute,the freedom degrees was low,the impact range was limited,the motion range was interfered and the impact process of the complex parts such as the blade cannot be perfomed.By constructing a laser shock peening system with multi-parameter integrated control to solve these problems.The entire system contains lasers,manipulators with control cabinets,water circulation systems,external optic systems,and PC off-line software systems.All parts are linked to each other.In the working space,the specimens can be freely rotated.This system can achieve a complex surface laser shock peening through a new laser peening process.(2)ABAQUS finite element software was applied to simulate the laser shock peening of 6061-T6 aluminum alloy specimens of one-layer,two-layer and threelayer lasers,providing a theoretical support for multi-layer laser shcok peening on aluminum alloys.With the increase of laser shock layers,the residual compressive stress on the surface of 6061-T6 aluminum alloy increased and the distribution of residual stress became more uniform.The stress was "compressive stress-tensile stress-compressive stress" distribution form in the vertical direction of the cross section.After multi-layer laser shock peening,plastic deformation obviously occurred on the surface of the 6061-T6 aluminum alloy specimen.The overall material macroscopic plastic deformation occurred due to the mechanical balance in the model,with the increase of the numbers of peening layers,the "arch-bridge" macroscopic deformation became more significant.(3)The laser shock peening system with multi-parameter integrated control was applied to perform 1,2,and 3-layer laser shock peening on the 6061-T6 aluminum alloy specimens.The influence in the electrochemical corrosion performance due to the changes in residual stress,microstructure and surface roughness of the material after multi-layer laser shock peening was researched.After multi-layer laser shock peening,the maximum residual compressive stress on the surface of the specimen was raised from-68 MPa(1 layer)to-107 MPa(3 layers),The surface microhardness was increased from 110 HV(as machined)to 188 HV(3 layers),the surface roughness droped with the increase of the number of peening layers.The depth of the grain refinement layer on the surface of the specimen increased from 130 ?m(1 layer)to 170 ?m(3 layers).After multi-layer laser shock,the electrochemical corrosion potential of 6061-T6 aluminum alloy shifts positively,electrochemical impedance increases,corrosion current decreases,and the material exhibits better corrosion resistance.The residual compressive stress,grain refinement and low surface roughness induced on the surface of 6061-T6 aluminum alloy are beneficial to improvement of the electrochemical corrosion resistance of the material,the corrosion of the material surface is reduced,and the size of the corrosion pits is decreased.(4)The laser shock peening system with multi-parameter integrated control was applied to perform 1,2,and 3-layer laser shock peening on 6061-T6 aluminum alloy specimens on both sides.The tensile property of aluminum alloys after different layers laser shock peening were researched.The morphology of the fracture surface was characterized,and the influence mechanism of laser shock peening layers on the tensile property of 6061-T6 aluminum alloy material was revealed.Double-sided multi-layer laser shock peening enhancement has greatly improved the ultimate tensile strength of the specimens.After 3-layer peening,the ultimate tensile strength of the specimen raised to 255 MPa,a total increasement of 13.3% compared to the ai machined specimen.The elongation of the material decreased firstly and then increased,from 13.6% of the as machined specimen to 11.3% after 1-layer peening,and then to 14.3% after the 3-layer peening.After 3-layer peening,the dimples size more evenly distributed in the fracture surface of the tensile specimen,about 10 ?m in average and the dimple density increased.The effect on surface grain refinement,residual stress distribution,surface roughness on crack initiation and propagation under multi-layer peening was analyzed,and the mechanism of laser peening layers on the tensile property of 6061-T6 aluminum alloy was revealed.