Tribological Properties And Numerical Simulation Of Al-Si-Pb Alloy By High Current Pulsed Electron Beam Modification

This dissertation focuses on the tribological properties of as-cast and hot extruded Al–Si–Pb alloys irradiated by high current pulsed electron beam (HCPEB). All experiments were investigated under dry sliding conditions using a pin-on-disc type wear testing machine. The HCPEB parameters used to treat the samples are: electron energy: 15–25 keV; energy density: 1.5–2.5 J/cm2; pulse duration: 1.5 As; number of pulses: 15. The formation of craters reveals that HCPEB irradiation changed the surface morphology of Al–Si–Pb alloy considerably. Cross-sectional EPMA and SEM images of the untreated and irradiated samples give a direct observation on microstructures suggests a corresponding improvement in mechanical properties. These factors contribute to great increase in wear resistance of HCPEB irradiated Al–Si–Pb alloys at 2.0J/cm2 and 2.5 J/cm2. Optical observation and X-ray photoelectron spectroscopy (XPS) analysis reveal that the low wear rate and lowest level in coefficient of friction at high load levels for Al–Si–Pb alloys HCPEB irradiated with more than 1.5 J/cm2 are due to a film of lubricant covering almost the entire worn surface. This film is a mixture of different constituents containing Al, Fe, Si, O and Pb, in which Pb exists in the form of Pb4SiO6. With the applied load increased, the dominant wear modes exhibit successively the oxidative wear, film spalling, and adhesive wear.Based on experimental investigation and physical models, the temperature field and stress field are simulated for Al-Si-Pb alloy. The starting melting position, the largest crater depth, melting layer thickness, and quasistatic stress distribution are obtained. These results reveal the mechanism of crater formation on the surface and hardness characteristics along the depth.