Preparation And Properties Of Homogeneous Al-Pb Alloy

In this thesis, the research progress of Al-Pb bearing alloys is reviewed. The microstructures, especially the amount and distribution of Pb particles in Al-Pb bearing alloys prepared by cooling slope casting and double-barrel mechanical stirring have been studied. The partial remelting and thixoforming of the obtained Al-Pb ingots alloy have also been studied. The fabrication techniques and composition of Al-Pb alloys were optimizated by tribological properties. The main conclusions are given in the following.1. The Pb particles do not distribute uniform completely in the matrix because the shear force mechanical stirring method.2. A double-barrel mechanical stirring device which can generate strong shear force to break the dendrite has been developed.3. Stirring technique of the double-barrel mechanical stirring device for preparing Al-Pb immiscible alloys has been studied. The effects of stirring temperature and speed on microstructures have been researched. The results show that homogeneous Al-Pb immiscible alloys can be under the stirring temperature of 595℃and speed of over 1000 r/m.4. The effects of casting parameters, such as pouring temperature, flow length and angle of the cooling slope plate casting on microstructures of the Al-Pb bearing alloys have been studied. An optimal casting technique has been developed, the pouring temperature of 1200℃, flow length of 1.2 m and flow angle of 45.5. The effects of alloying elements and ingot size on microstructures of the Al-Pb bearing alloys prepared by cooling slope casting have been studied. The results show that the Pb particle size increases as the diameter of casting ingots or the Pb amount increase. Simultaneously, the Pb segregation occurs.6. Some theoretical problems during preparation of Al-Pb alloys by cooling sloping plate process have been explored. It shows that the cooling slope plate technology in the preparation of uniform Al-Pb alloys is feasible. The chilling effect of the cooling slope plate can make the Stokes moving speed, Us, and the Marongoni moving speed Um to be canceled out, resulting in the no obvious segregation of Pb and the alloy ingots with quite uniformly distributed Pb particles.7. The microstructural evolution during partial remelting of the Al-Pb bearing alloy ingots has been researched. It shows that the appropriate remelting process is the heating for 150min at 615℃.8. The thixoforming process of the obtained Al-Pb alloy ingots has been investigated. At the same time, the mechanical and thribological properties of the thixoformed alloys have been studied. An optimal forming technique has been developed, the reheating temperature of 615℃, heating time of 150 min and injection speed of 5 m/s. The bulk material with friction coefficient less than 0.35 can be obtaind.