Preparation, Microstructure And Properties Of Silver-based Multi-component Alloys

In this paper, silver based multi-component alloys are prepared by powder metallurgy, and the purpose of this study is to design a kind of electrical contact material with certain strength, good conductivity and wear resistance. In the processing of silver-based alloys, first of all the Ag-Cu, Ag-Cu-RE and Ag-Cu-Ni-RE alloy powders are prepared by mechanical alloying method, the influnce of the milling parameters, RE elements and transition metals on the degree of alloying powder are analyzed. Then the content of silver based multi-component alloy is designed, and the effects of component and processing on microstructure and properties are discussed, and the frictional and wear proerties of alloy are studied.The results obtained are:(1) During the process of mechanical alloying, as the increase of ball-milling time, gradually, the XRD peak width of Ag-Cu powders increases, peak intensities decreases and the grain size decreases. With addition rare earth and transition elements such as Zr, Fe, the solution degree of Cu in Ag phase increases, and the mechanical alloying process is accelerated, Zr has a better impact. On the contrary, the addition of Cr leads to the decrease of the solution degree of Cu in Ag phase.Mechanical alloying method was also used to prepare Ag-Cu-Ni-Sm alloy powders. With the increase of ball-milling time, the solution degree of alloy powder, the lattice constant and the aberrance extent of Ag (111) all increase. After annealing at 400℃, the alloying effect of the powder still remains.(2)Powder metallurgy method was used to manufacture AgCuNiSm composite materials. During the pressing process of alloy billet, the difficulty of cold repression increases with the content of composite powders in the composite material increasing. Resintering can effectively increase the density of composite materials and reduce the porosity ratio of the composite. The addition of the rare-earth element Sm can lower the degree of densification, the higher the content of Sm and the worse the density of composite materials. Long time and high temperature thermal favors the diffusion of alloying elements and increase of the density of materials. With increasing the content of Ni, the hardness of composites improves and flexural strength decreases, while the conductive performance reduces. At cold repression process, with increasing the content of composite powders, it is difficult to achieve higher density of composite, and so the bending strength and electrical conductivity are lost. When the content of Ni in the composite material is 0.5%, the composite powder can effectively strengthen the matrix, and has little effect on resistivity, and as a result, AgCuNiSm alloy has good overall performance. Appropriate addition of rare earth element Sm can enhance the AgCuNiSm alloy strength and hardness, reduce resistivity.(4) The results of the wear experiments on the AgCuNiSm alloy indicate that: with increasing the alloy after mechanical alloying powder content, both the friction coefficient and the wear volume of composite materials increases; the rare-earth elements can effectively improve the wear resistance of composite materials, decrease the wear volume and the friction coefficient. Abrasive wear and adhesive wear are the main wear mechanism of AgCuNiSm multi-component Alloy.