Research On The Microstructures And Wear Characteristics Of Multielement Alloy Al-10Si-5Cu-0.75Mg

Aluminum alloy is widely used in the automotive industry due to it's light weight,high specific strength,as well as good comprehensive mechanical properties,satisfies people's demand for safe and comfort,energy-saving and environmental protection.In this paper,Al-10Si-5Cu-0.75 Mg alloy was prepared through optimizing design on the basis of the traditional aluminum alloy.Heat treatment is one of the most economical and effective methods to improve the performance of Al-10Si-5Cu-0.75 Mg alloy.In this paper,the impacts of heat treatment on the microstructure and mechanical properties of Al-10Si-5Cu-0.75 Mg alloy were researched by methods of SEM,XRD,EDS,DSC and so on,and the best heat treatment technology was optimized.The load and revolving speed on the influence of friction and wear performance between the as-cast,solid solution state,solid solution aging state alloy were analyzed.The structures and roughness of worn surfaces,cross-section subsurfaces and wear debris were measured and discussed thoroughly by adopting SEM,EDS,CLSM et al,and the wear mechanism of the alloy was explored.The research results are as follows:Al-10Si-5Cu-0.75 Mg cast alloy is composed of primary ?(Al)phase,eutectic Si phase,Al2 Cu phase and Mg2 Si phase composition.Its mechanical properties are: the?b= 275 MPa,brinell hardness is 102 HB.The melting point of the alloy is 606.8 ?.The optimal heat treatment processes of Al-10Si-5Cu-0.75 Mg alloy are solid solution at 500 ? for 8 h plus artificial aging at 190 ? for 6 h following air cooling.The alloy grains are refined through the process of solid solution and aging treatment,and the second phases in the alloy are immersed in the matrix,as well as supersaturated solid solution are formed by precipitation strengthening.The strength and hardness of the alloy are significantly improve through those methods.After solid solution at 500 ?for 8 h,the tensile strength grows to 365 MPa,brinell hardness grows to 142 HB,increases by 32.7% and 42.8%,respectively compared with as-cast alloy.Artificial aging at 500 ? for 8 h,the tensile strength further increases to 385 MPa,brinell hardness grows to 163 HB,increases by 40% and 59.8%,much higher than the as-castalloy.The heat treatment process has a very important influence on the wear rate,as well as the friction coefficient and roughness value.In the condition of the same load and rotational speed,the wear rate and friction coefficient of the as cast alloy are the highest.The results show that the wear resistance of the solid solution aging state of the alloy is the best,the wear resistance of the solid solution alloy is the second,and the wear resistance of the as cast alloy is the worst.However,the friction coefficient of the three kinds of alloy can keep stable with the wear time,which indicates that the friction coefficient of Al-10Si-5Cu-0.75 Mg alloy is not sensitive to time and has the ability of sustained and stable wear resistance.The influences of load and speed on the wear rate,friction coefficient and roughness of Al-10Si-5Cu-0.75 Mg alloy are different.The wear rate and wear surface roughness increase with the enhance of load,and the friction coefficient decreases with the increase of load.The interference behavior of the asperity on the wear surface decreases with the increase of the load,which leads to the decrease of the friction coefficient.At low load,the wear mechanism is mainly abrasive wear and slight adhesive wear,accompanies by a small amount of oxidation wear.At high load,the wear mechanism changes into adhesive wear,fatigue wear,delamination wear and severe oxidative wear.The friction and wear properties of the alloy are significantly affected by the rotational speed.The wear rate increases and the friction coefficient decreases.The friction heat enhances with the increase of rotational speed generated in the friction process,accelerates the formation of the oxide,increases the coverage of the oxide film,and leads to the decrease of the friction coefficient.At low speed,the wear mechanisms of the material are mainly abrasive wear and a small amount of oxidation wear.In the high speed,the wear mechanisms are fatigue wear,delamination wear and oxidation wear.