A Study On Electrical Sliding Wear Properties Of Al-Cu Alloy

The rapid development of high-speed and heavy-load of modern rail transit system raise higher requirements for the service life and current receiving quality of electric sliding friction pair.Al-Cu alloy can meet the requirements of modern high-speed train for high-performance electric sliding friction pair materials because of the advantages,such as high specific strength,good conductivity,thermal conductivity,high-temperature performance and good corrosion resistance.In this paper,the microstructure distribution of Al-Cu alloy was changed by adding different content of Cu element and refiner（Al-5Ti-B）,and the electric sliding wear test was carried out under different current density and sliding speed.The effects of microstructure and working conditions of Al-Cu alloy on the evolution of electric sliding wear mechanism of Al-Cu alloy were discussed from the aspects of wear rate,macro and micro morphology of worn surface,wear debris and surface temperature rise.It was expected to provide a basic theoretical basis for the composition design and optimization of Al-Cu alloy as electric sliding friction pair material.The effects of Cu and refiner content on the microstructure and basic properties of Al-Cu alloy were studied.The results show that the eutectic structure of Al-Cu alloy changed from particle or thin-strip distribution to uneven bulky network distribution in the boundary of primaryα-Al grain with the increase of Cu content,the strengthening of Al₂Cu“excess phase”intensified.The hardness,density and tensile strength of Al-15Cu were higher than Al-5Cu,while the elongation and conductivity decreased.With the increase of refiner content,the eutectic structure of Al-15cu alloy changed from bulky network distribution to island or small continuous distribution,the particle diameter of primaryα-Al decreased,while the shape factor increased.The strengthening effect increased sharply at first and then tended to be stable.The addition of Al-5Ti-B refiner could improve the hardness,tensile strength,elongation and conductivity of Al-15Cu alloy.The law of variation for wear properties of Al-Cu alloys with different Cu and refiner content at different current densities were studied,and the wear rate,macro and micro morphology of worn surface,wear debris and surface temperature rise were analyzed.The results showed that the wear rate of Al-Cu alloy generally rose with the increase of current density,the wear resistance of Al-Cu alloy was greatly affected by Joule heat and arc heat.The wear rate of Al-Cu alloy increased greatly and the wear mechanism changed from adhesive wear to abrasive wear with the increase of Cu content,the generation of large-scale“continuous chips”at the initial stage of wear and the speed of the formation of materials transfer layer directly caused the difference of wear rate of Al-Cu alloys with different Cu content.The wear mechanism of refined Al-15Cu was adhesive wear,abrasive wear and delamination wear in the condition of non-current sliding wear and the adhesive wear and delamination increased,while the abrasive wear decreased with the increase of the content of refiner.The uniformly distributed patch eutectic adhesive appeared on worn surface of refined Al-15Cu alloy in electric sliding wear,which could disperse the load and hinder the continuous plastic deformation of the material,so as to slow down the wear rate of the material.The law of variation for wear mechanism of Al-Cu alloy under different microstructure was discussed.The electric sliding wear process of Al-Cu alloy could be divided into the three stages:chiseling stage,material transfer layer and mechanical mixing layer formation stage,delamination stage.The bulky eutectic“skeleton”was prone to brittle fracture due to local stress concentration.The bulky eutectic“skeleton”could be dispersed by adding refiner and the phenomenon of stress concentration could be effectively alleviated,and the improvement of alloy plasticity after fine grain strengthening also promoted the formation of material transfer layer and mechanical mixing layer,which could reduce the wear rate.The effect of sliding speed on the electric sliding wear properties of refined Al-15Cu alloy was studied.The results show that the wear rate of Al-15Cu alloy decreased with the increase of sliding speed,the plastic deformation of the worn surface was serious at high speed,and the adhesion of silver white wear debris appeared,resulting serious arc erosion.The adhesion bore the load,which could protect the alloy.The wear mechanism of Al-15Cu alloy changed from abrasive wear to delamination wear,adhesive wear and abrasive wear,and arc erosion with the increase of sliding speed.