Study On The Effect Of Nd And P Elements On The Surface Modification Of Al-Si Alloy By High Current Pulsed Electron Beam

As an important material surface modification technology,the high-current pulsed electron beam(HCPEB)technology has been widely used in the fields of semiconductor materials,metal materials and polymers in recent years due to its environmental protection,high efficiency,and low energy consumption.However,a large number of micro-crack and crater defects are inevitably produced on the surface of the material processed by HCPEB.The formation of these defects greatly limits the industrial application of the HCPEB technology.Early studies by some scholars have shown that the addition of Nd elements can effectively eliminate micro-crack defects,but the effect of eliminating crater defects has not been clarified.In addition,there are few reports on the compound modification of P element,which is the same modifier element as Nd,and HCPEB technology.In this paper,the effects of Nd and P on the surface modification of Al-Si alloy treated by HCPEB were studied.The Al-17.5Si alloy was compound modified by Nd,P inoculation and HCPEB treatment.The surface microstructure and properties of Al-17.5Si alloy were studied before and after compound modification.The results are summarized as follows.When no metamorphic elements were added,a large number of craters were formed on the surface of the alloy after 25 pulses treatment;irregular nanometer silicon particles was formed on the surface of the alloy;no new phases appeared on the surface of the alloy;the alloy surface performance test results show that the hardness of the aluminum matrix on the surface of the alloy increased from 59.6HV of the original alloy to 96.0HV after 25 pulses treatment,and the friction coefficient decreased from 0.5308 of the original alloy to 0.4656 after 25 pulses treatment.The current density increased from 8.896×10-6 A/cm2 of the original alloy to 9.978×10-5 A/cm2 after 25 pulse treatment.When Nd elements were added,no new phase appeared on the surface of the alloy,but the preferred orientation of the aluminum crystal plane appeared,the craters were effectively eliminated after the addition of Nd elements,spherical nano silicon particles are formed on the surface of the alloy,Nd elements are uniformly distributed on the surface of the alloy.The alloy surface performance test results show that the hardness of the aluminum matrix on the surface of the alloy increased from 66.7HV of the original alloy to 108.1HV after 25 pulses,and the friction coefficient decreased from 0.5488 of the original alloy to 0.4848 after 25 pulses.The current density It decreased from 6.822×10-5 A/cm2 of the original alloy to 9.845×10-7 A/cm2 after 25 pulses treatments.When P elements were added,the surface phase and morphology analysis show that,when the addition amount of P element is 0.8%,the effect of refining the primary silicon on the surface of the Al-17.5Si alloy is the best,the surface of Al-17.5Si-0.8P alloy formed a typical crater defects,pure Al particles and micro-pore morphology after 5 pulses treatment,and formed peritectic structure after 15 pulses treatment,the craters of Al-17.5Si-0.8P alloy are eliminated after 25 pulses treatment,the diffraction peaks on the alloy surface have a certain degree of broadening and high angle deviation.The alloy surface performance test results show that the hardness of the aluminum matrix on the surface of the alloy increased from 67.4HV of the original alloy to 108.3HV after 25 pulses treatment,and the friction coefficient decreased from 0.5318 of the original alloy to 0.4251 after 25 pulses treatment,the current density from 1.079×10-4 A/cm2 of the original alloy to 1.959×10-6 A/cm2 after 25 pulse treatments.In conclusion,the addition of rare earth Nd element can effectively eliminate the craters produced by the HCPEB treatment process,and induce the spheroidization of nano silicon particles,which significantly improves the wear resistance and corrosion resistance of the alloy;the addition of P element can also eliminate craters while achieving grain refinement,thereby improving the surface micro-hardness,wear resistance and corrosion resistance of the alloy.The addition of trace elements provides a new idea for further expanding the industrial application of HCPEB technology.