Papers by Author: Chang Sheng Liu

Abstract: Anodic oxide films were prepared firstly on the surface of a 2024 aluminum alloy. Then the effect of different heat-treatment temperatures on the structure and properties of the films was studied. The results indicate that the construction units of Al2O3 oxide film were composed of tubules less than 100nm in external diameter, and the film became more compact and uniform as a result of the increased temperature after the heat treatments of 100, 150, 200, 250, 300, 350, and 400°C under the protection of a H2 atmosphere. The hardness of the films increased linearly with the increase of heat treatment temperature; whereas the wear loss tended to decrease first and then increase. After being treated at the temperature of 250°C, the hardness reaches 606HV, the wear loss is a minimum of 11mg. The structure of the film heat-treated at 250°C has a compact structure, higher hardness, and the best wear resistance.

Abstract: Using atomizing Cu-Ni-Sn-Pb powder as the matrix alloy and adding 2wt% graphite as solid lubricant phase, a Cu-based self-lubricating composite reinforced with SiC ( with 0wt%, 1wt% and 2wt%14µm SiC) was prepared under the optimized powder metallurgy sintering condition. The structure and properties of the samples were analyzed using a scanning electron microscopy, X-ray diffraction, a tensile tester, a hardness tester, and a friction tester. The results indicate that the prepared sample of 1wt%14µm SiC, when sintered at 910°C for 4 hours, possessed a perfect composite structure in alloy strengthening, graphite lubrication and SiC particle reinforcing. The main phases consisted of α-solid solution of copper, CuNi2Sn, Pb, graphite, and SiC. The wear loss was 12.6mg and the friction coefficient was 0.26. SiC particles reinforcement was optimized using fine grain to enhance the anti-wear and self-lubricating properties of the alloy matrix.