Study On The Effect Of Ultrasonic Rolling On The Microstructure And Properties Of 316L Stainless Steel And Mg-Al-Zn Alloy

Metal material parts have been widely used in actual production and have become the foundation of modern industrial development.However,the failure of metal materials seriously affects the service life of the material,among which fracture,wear,and corrosion are the three main failure modes.Therefore,continuous improvement of the mechanical properties,wear resistance and corrosion properties of metal materials is an eternal research theme and hot spot in this field.This subject uses ultrasonic rolling technology,selects two engineering materials with typical characteristics: 316 L stainless steel and AZ91 magnesium alloy,studies the preparation technology of high-performance plates based on ultrasonic rolling processing methods,and discusses the easy deformation and resistance of ultrasonic rolling processing.The formation mechanism of surface formation,surface properties and surface microstructure of corroded metal(316L stainless steel)and difficult-todeform and easily corrosive metal(AZ91 magnesium alloy).The mechanical properties,corrosion properties,and wear properties of two metal materials by ultrasonic rolling have been studied.The specific content is as follows:USR produces gradient nanostructures on the surface of as-cast AZ91 magnesium alloy.The grain size of the surface layer is refined from coase grain of the original sample to 53 nm,and a large number of dislocations and twins are generated in the subsurface layer,and the thickness of the hardened layer reached 1mm.The mechanical properties and surface quality of AZ91 magnesium alloy are significantly improved after USR: surface roughness is 0.036 μm,which is 4.7 times lower than before rolling;surface hardness is 100 HV,which is an increase of 41%;yield strength and tensile strength are increased by about 50%,while the elongation rate remains basically unchanged.USR also improves the corrosion performance of AZ91 magnesium alloy in 3.5% Na Cl solution.After USR,the corrosion current density is reduced by about65%.The improvement of mechanical properties is mainly attributed to the strengthening effect of fine nanocrystals in the gradient nanolayer;the improvement of corrosion resistance mainly comes from the improved surface roughness,uniform surface structure and residual stress.USR produces gradient nanostructures on the surface of 316 L stainless steel,and the surface grain size is refined from 18 μm of the original sample to 6-16 nm.After USR the surface roughness of 316 L stainless steel is increased by 20 times,reaching Ra 0.8μm;the surface hardness is increased by 61%,reaching 290 HV.Further research shows that the wear of 316 L stainless steel after USR is about 20 times lower than that of untreated,and the wear resistance is greatly improved.At a speed of 200 rpm,the 316 L stainless all show the oxidative wear,abrasive wear and slight adhesive wear.When the speed is increased to 400 rpm,the wear machine causes serious adhesive wear and abrasive wear to turn into slight adhesive wear and oxidative wear.At the same time,the corrosion current density of 316 L stainless steel is reduced by 2 times,and the corrosion performance is simultaneously improved.The improvement of wear resistance is closely related to the surface roughness and surface grain refinement.