Control Of Microstructure And Wear Properties Of Cast Aluminum Alloy By High Frequency Electric Pulse

In cast aluminum alloys α-The morphology and size of Al and eutectic Si are extremely important for their microstructure and properties.Electric pulse processing,as a new technology for improving the solidification structure of metals,can improve related properties by regulating the microstructure of alloys。This article uses a pulse current output device to apply different high-frequency pulse current parameters to Al-9Si binary alloy,Study on the Influence and Regulation Mechanism of High Frequency Electric Pulse on the Microstructure of Hypoeutectic Al-Si Alloy,Revealing the mechanism of electric pulse on microstructure refinement and morphology optimization of Al-9Si binary alloy;Study the effect of electrical pulse parameters on the friction and wear properties of Al-9Si binary alloy,and reveal the strengthening mechanism of electrical pulse regulation on the properties of Al-9Si binary alloy 。The main conclusions of the paper are as follows:(1)By changing the high-frequency electrical pulse parameters,the microstructure of hypoeutectic Al-9Si alloy can be adjusted.Increasing the pulse voltage and frequency of electrical pulses can make α-The Al phase mostly turns into a spherical shape,and there are also many equiaxed crystals generated,with an average size of 38 μ M to 15.2 μm;The eutectic structure exhibits uniform dispersion distribution,with significant refinement effect and more uniform distribution.As the pulse width decreases,the microstructure is refined.(2)When the pulse voltage is 150 V,the pulse frequency is 1000 Hz,and the pulse width is 5 ms,the refinement effect of the alloy solidification structure is the best,α-Al transforms from dendrites to spheres,with obvious passivation effect on edges and corners,and its arrangement becomes very regular and orderly;α-The solid solubility of Si in Al reached a maximum of 2.05%;Eutectic Si in α-The distribution between Alis more dispersed and uniform,and the grains are elongated and needle like with directionality.(3)The results indicate that applying high-frequency electrical pulses during the solidification process will generate different shrinkage forces at different positions within the metal melt,resulting in different flow abilities at different parts of the melt.The differences in flow abilities will cause gradient generation,and the internal shear stress will naturally appear,which will break down the intact dendritic crystals and free them back into the alloy melt,becoming new crystal nuclei,This can refine the grain size.(4)In the friction and wear test,the average friction coefficient of the alloy significantly decreases with the increase of pulse voltage and pulse frequency;As the pulse width increases,it significantly increases.The average friction coefficient of the unmodified alloy is 0.485,reaching a minimum value of 0.281 when the pulse voltage is 150 V,and the average friction coefficient decreases by 42.1%;When the pulse frequency is 1000 Hz,it reaches the minimum value of 0.302,and the average friction coefficient decreases by 37.7%;When the pulse width is 5 ms,it also reaches the minimum value of 0.213,and the average friction coefficient decreases by 56.1%.(5)The micro Vickers hardness of the alloy increases significantly with the increase of the pulse voltage and pulse frequency of the electric pulse;As the pulse width increases,it decreases significantly.The micro Vickers hardness of the unmodified alloy is 49.94 HV,reaching a maximum value of 53.8 HV at a pulse voltage of 210 V;When the pulse frequency is 1000 Hz,it reaches the maximum value of 54.13 HV;When the pulse width is 5 ms,it also reaches the maximum value of 57.48 HV.In summary,when the pulse voltage is 150 V,the pulse frequency is 1000 Hz,and the pulse width is 5 ms,the comprehensive mechanical properties of hypoeutectic aluminum silicon alloy reach the best.