Effect Of Microarc Oxidation And Hard Anodizing On Mechanical Properties Of 7050 Aluminum Alloy

The application of aluminum alloy in aircraft,ship and automobile is limited because of its friction resistance and poor corrosion resistance.However,choosing suitable surface treatment technologies such as micro-arc oxidation and hard anodic oxidation technology can improve its wear resistance and corrosion.However,the effect of surface treatment on the mechanical properties such as fatigue and tensile properties of aluminum alloy parts must also be considered in the actual service process.However,the effect of surface treatment on the mechanical properties such as fatigue and tensile properties of aluminum alloy parts must also be considered in the actual service process.In this paper,anodized and micro-arc oxidation coatings of 8?m,16?m and 24?m were prepared on the surface of 7050 aluminum alloy.The HT-9711 fatigue test equipment,HT-2402 tensile test equipment,and UMT TriboLab friction and wear test equipment system were used to study the variation of aluminum alloy tensile,fatigue,and surface friction and wear behavior after micro-arc oxidation hard anodizing.The phase structure of the film was analyzed by XRD,the microstructure of the film was analyzed,tensile and fatigue fracture morphology,wear morphology by SEM.and Finally,the effect of two surface treatment technologies on fatigue,tensile and friction wear behavior of aluminum alloy is clarified.The results show that the micro-arc oxidation coating on the surface of 7050 aluminum alloy is mainly divided into two layers:the inner layer is a dense layer,and the outer layer is a loose porous layer.The tensile properties of 7050 aluminum alloy after micro-arc oxidation and hard anodization were reduced.The yield strengths of micro-arc oxidation film thicknesses of 8?m,16?m,and 24?m were decreased by 2.04%,2.13%,and 4.01%,respectively,and the tensile strength decreased.1.4%,1.54%,3.2%;the hard anodized thickness of 20?m,40?m yield strength decreased by 2.3%,3.7%,tensile strength decreased by 1.7%,4.0%,respectively.Micro-arc oxidation and hard anodic oxidation decreased the reduction in area less than 5%,and both showed plastic fracture.The fatigue limit of the aluminum alloy matrix is 235MPa,and the fatigue limits of the micro-arc oxidation treated aluminum alloy specimens with film thicknesses of 8?m,16?m,and 24?m are 163MPa,155MPa,and 136MPa,respectively.The fatigue strength of the hard anodic oxide film thickness is 24?m is 116MPa.This shows that the fatigue strength of aluminum alloys after micro-arc oxidation and hard anodic oxidation is significantly reduced,and the anodic oxidation is reduced by more than 50%.Friction and wear test results show that the surface friction coefficient of aluminum alloy after micro-arc oxidation and anodizing treatment is significantly reduced,and the friction coefficient decreases with the increase of film thickness.When the thickness is the same,the greater the load is,the smaller the friction coefficient is.The change trend of hard anodic oxidation and micro-arc oxidation is basically the same,but the friction coefficient of hard anodic oxidation is larger than that of micro-arc oxidation at the same thickness or load.The wear pattern of aluminum alloy substrate is plow wear and adhesive wear;the thickness of micro-arc oxidation ceramic layer is 8?m,16?m,the main wear pattern is abrasive wear,and the wear pattern of 8?m hard anodized sample at 3N is mainly Ploughing wear and slight abrasive wear,the wear pattern at 5N is mainly adhesive wear and plough wear,and the 16?m hard anodized sample wear pattern is mainly abrasive wear.