Effect Of Combination Modification And Alloying On Microstructure And Grinding Properties Of Al-13%Si

Aluminum-silicon alloy is suitable for the manufacture of heat and wear-resisting parts of automobile engine piston,cylinder block and machinery manufacturing because of its advantages of light weight,good wear-resisting and heat-resisting,small thermal expansion coefficient and so on.However,the morphology of eutectic silicon and primary silicon is relatively large,which makes the matrix distribution discontinuous and presents unideal mechanical properties and machining properties in the as-cast state.In addition,it also causes serious tool wear,surface roughness.Therefore,optimizing the microstructure of primary silicon and eutectic silicon in the alloy and improving the comprehensive properties of the alloy are the necessary steps to promote the application of Al-Si alloy in more fields.In this paper,Al-13%Si alloy was used as the object of composite modification and alloying,and the effects of the two treatment methods on the microstructure of the alloy were investigated.At the same time,the grinding force,grinding force ratio,grinding specific energy,surface topography and surface roughness were measured by means of high precision surface grinding machine,Kistler dynamometer,scanning electron microscope,ultra-depth of field microscope and roughness measuring instrument.The effects of workpiece moving speed(Vw),grinding depth(Ap)and grinding wheel material on the grinding performance of compound modification and alloyed Al-13%Si were investigated.The results showed that:(1)The composite modification significantly improves the microstructure of the alloy.The A(Al)phase with the addition of 0.04%Sr and 0.5%Zr has the best refining effect,and the columnar and secondary dendrites are fused and transformed into equiaxed grains.Adding 0.04%Sr,0.5%Zr and 0.6%Re to the alloy,the primary silicon modification effect is the best,and the bulk microstructure changes into fine particles.When 0.04%Sr and 0.6% Re are added to the alloy,the eutectic silicon has the best modification effect,and the long needle-like microstructure changes into fine granules,which are uniformly distributed in the matrix.The effect of alloying on the microstructure is weak,and the dendritic dendrites of α(Al)phase show a growing trend,and the modification effect of primary silicon is not obvious.When 4%Cu and2%Bi are added to the alloy,the eutectic silicon becomes a short rod-shaped or granular eutectic silicon structure,which is similar to the grid distribution in the matrix.(2)Under the same grinding conditions,the effects of grinding parameters on the grinding properties of composite modification and alloyed Al-Si alloys show the same change rule.The effect of Ap on grinding force is better than that of Vw,and the greater the Ap,the greater the grinding force.The influence of Vw on grinding force ratio and grinding specific energy is better than that of Ap.The higher the Vw is,the higher the grinding force ratio and grinding specific energy are.(3)The influence of Vw on roughness is better than that of Ap,and the higher the Vw is,the rougher the surface is.(3)When Ap =8μm and Vw =5m/min,the grinding force,grinding force ratio and grinding specific energy are all the minimum when0.04%Sr and 0.6% Re are added to the alloy.At the same time,the surface quality of the workpiece is the best and the surface roughness is the smallest,which is 0.129μm.(4)When Ap=5μm and Vw=10m/min,the grinding force,grinding force ratio and grinding specific energy are all minimum when 4%Cu and 2%Zn are added in the alloy.The pores and microcracks were reduced,and the surface morphology was better,with the lowest roughness of 0.135μm.(5)Under the same grinding parameters,the grinding force and grinding force ratio of composite metamorphic and alloyed Al-Si alloys can be reduced by using cubic boron nitride wheel.The phenomenon of tearing,holes and micro-cracks on the workpiece surface is reduced,and better grinding surface quality is presented.Resin diamond grinding wheel has a small specific grinding energy when grinding the alloy with high hardness,which is suitable for grinding the aluminum-silicon alloy with high silicon content.