Research On The Wear Mechanism And Friction Deformation Behavior Of AZ31 And GW83 Magnesium Alloys

The development of high-performance lightweight materials is an important way to promote carbon neutrality and implement the spirit of the 20th National Congress of the Communist Party of China.In this context,magnesium alloy,as the lightest metal material in engineering applications and has not been fully developed,is receiving unprecedented attention.Friction and wear is one of the main forms of metal failure,which will have a significant impact on the performance and service life of magnesium alloy parts.At the same time,friction and wear are also essential considerations in processes such as plastic forming.Therefore,it is necessary to systematically and deeply study the friction and wear behavior of magnesium alloy materials.As the source of wear debris,the deformation and damage behavior of the friction contact surface and its adjacent area（friction subsurface）ultimately determine the wear resistance of magnesium alloys by affecting the wear mechanism.However,the complex thermal-stress coupling in the sliding contact process makes it difficult to clarify the mechanism.In this case,the typical representatives of traditional wrought magnesium alloys and high-performance rare earth magnesium alloys（AZ31,GW83）were selected respectively.The effects of tribological parameters on the friction and wear properties of magnesium alloys were systematically studied by low-speed sliding and water-cooling devices to reduce the friction heat.Optical microscope（OM）,scanning electron microscope（SEM）,electron backscatter diffraction（EBSD）,3D profilometer,microhardness tester and material tensile machine were used to systematically study the microstructure and mechanical properties.The wear mechanism was clarified by analyzing the wear mechanism and the evolution of the microstructure of the friction subsurface.The wear mechanism was clarified by analyzing the wear mechanism and the evolution of the microstructure of the friction subsurface.The research results can provide experimental basis and theoretical basis for the development of wear-resistant magnesium alloy and the wear-resistant surface modification technology of magnesium alloy materials.First,the friction and wear behavior of AZ31 magnesium alloy rolled sheet under different normal loads（100 N-800 N）was studied.The results show that in the load range of 100 N-800N,with the increase of load,the wear rate of AZ31 magnesium alloy rolled sheet gradually increases from 6.8×10^-2 mm³/m to 15.3×10^-2 mm³/m,and the friction coefficient decreases from 0.2948 to 0.2335.The change of friction and wear properties is related to the evolution of wear mechanism.At 100 N-200 N,the wear mechanism is mainly abrasive wear,and the thickness of friction deformation layer is 99μm-150μm.At 300 N,the wear is dominated by abrasive wear and slight delamination wear,and the thickness of the friction deformation layer changes little.400 N-500 N,the wear mechanism is mainly delamination wear,and the thickness of friction deformation layer is 192μm-200μm.At 600 N,the wear mechanism is mainly delamination wear and severe plastic deformation.700 N-800 N,the wear mechanism is mainly severe plastic deformation,and the thickness of the friction deformation layer increases rapidly to 316μm-349μm.Second,the effects of different sliding time（50 s-4800 s）on the friction and wear behavior of AZ31 magnesium alloy rolled sheet at 300 N were studied.The structure shows that when the load is 300 N,the wear rate of AZ31 magnesium alloy rolled sheet increases approximately linearly with the extension of sliding time.In 50 s-600 s,the wear mechanism of the alloy is mainly abrasive wear.When the sliding time is 1600 s-4800 s,the wear mechanism changes to delamination wear,and the degree of delamination wear gradually increases with the extension of sliding time.When the sliding time exceeds 2400 s,the degree of delamination wear remains basically unchanged.Third,the tribological anisotropy behavior of AZ31 magnesium alloy rolling sheet was analyzed by the influence of sliding direction on the friction and wear and friction deformation behavior of AZ31 magnesium alloy rolling sheet.The results show that the friction and wear properties of the rolled AZ31 magnesium alloy sheet are anisotropic.The wear rate when sliding parallel to the rolling direction（denoted as"∥RD"）is significantly lower than that when sliding perpendicular to the rolling direction（denoted as"∥TD"）.The change of wear mechanism caused by different plastic deformation behavior of friction subsurface is the main reason for the anisotropy of wear resistance of AZ31 magnesium alloy rolled sheet.When sliding in the∥RD direction,the integral number of twin crystals in the subsurface layer of the alloy is higher than that in the∥TD direction,indicating that it can better coordinate the plastic deformation caused by the friction shear stress,thereby reducing the degree of delamination wear and improving the wear resistance.Fourth,the texture-weakened GW83 magnesium alloy was prepared by adjusting the process parameters.The effects of tribological parameters and aging precipitation on the friction and wear behavior of magnesium alloy were studied.The results show that with the increase of sliding load,the wear rate of GW83 magnesium alloy extruded tubes in O state and T5 state increases rapidly and then increases slowly.The wear mechanism gradually changes from adhesive wear and abrasive wear to delamination wear.Under different normal loads,the wear resistance of the T5 state GW83 magnesium alloy extruded tube is significantly higher than that of the O state.This change is related to the precipitation strengthening phase,which reduces the plastic deformation degree of the subsurface layer,thereby reducing the effect of delamination wear and other mechanisms.