【作者】 赵健闯；

【导师】 安健； 刘海峰；

【作者基本信息】 吉林大学 ， 材料工程， 2006， 硕士

【摘要】 本学位论文主要研究热挤压态Al–Si–Pb合金经强流脉冲电子束HCPEB(High Current Pulsed Electron Beam)改性后的摩擦学性能及数值模拟。摩擦磨损试验是在干摩擦条件下在销-盘磨损试验机上进行的。用于处理试样的HCPEB(High Current Pulsed Electron Beam)参数是:电子能量:15-25 keV;能量密度:1.5–2.5 J/cm2;脉冲周期1.5μs;脉冲次数:15。熔坑的形成表明了HCPEB辐射改变了Al–Si–Pb合金的表面形貌。对比未辐射和辐射试样的断面EPMA和SEM图象,可以看出显微组织明显改善,相应地引起机械性能的提高。电子能量束密度为2.0J/cm2 and 2.5 J/cm2辐射的Al–Si–Pb合金的耐磨性显著提高。光学观察和X射线光电子分析表明: Al–Si–Pb合金在能量密度大于1.5J/cm2辐射的条件下,在高载荷作用下,表现出的低水平的磨损率和摩擦系数主要是由于在磨损表面形成几乎覆盖整个表面的润滑膜。这种薄膜是含有不同成分的Al, Fe, Si, O和Pb的混合物,其中铅的存在形式是Pb4SiO6。随着所施加载荷的增加,磨损形式依次表现为氧化磨损、薄膜剥落及粘着磨损。通过数值计算方法对Al-Si-Pb合金的温度场和应力场进行模拟,给出了最先熔化的位置、形成熔坑的最大深度、熔化区的最大深度以及准静态热应力的分布。通过合金的数值模拟结果和实验结果对比,揭示了表面熔坑的形成机制和剖面硬度分布特征。更多还原

【Abstract】 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.更多还原