Research On Microstructure And Properties Of Internal Oxidizing Ag-Mg And Ag-Mg-Ni Alloys

Ag is used as contact junction materials for its better electrical conductivity, heatconductivity and workable features. However, the more extensive application is limitedresulting from bad mechanical properties and arc corrosion-resistance. Much researchhas indicated that the addition of Mg and Re elements can strengthen Ag alloy by theway of internal oxidation after internal oxidizing treatment. Therefore, in this paper, thedifferent internal oxidizing characteristics of Ag-Mg and Ag-Mg-Ni are studied, and theinternal oxidation of Ag-Mg-Ni-Re alloy is preliminarily investigated based on theresearch.The research on various Ag-Mg alloys indicates that the electrical resistivity of thealloy shows little change and mechanical properties show obvious change after internaloxidizing treatment. With the increasing Mg, the hardness and strength increase andelongation decreases sharply. The experiment of TEM shows that the internal oxidizingparticle is MgO with fcc structure, and the size of MgO grows with increasing Mg andinternal oxidizing temperature, but the relationship between MgO size and the value ofMg or internal oxidizing temperature is not linable. The morphology of MgO is globularwith symmetric stress field, which shows better thermal stability and strengthen ability.With the addition of Ni in Ag-Mg alloy, the electrical resistivity and strength showlittle change, and elongation shows obvious increase. When the value of Ni reaches to acertain degree, the performance of Ag-Mg-Ni alloy shows unstability. The toughenedmechanism of Ni element mainly results from the disitribution of Ni particle in internalgrain and on grain boundaries, which decreases the amount of MgO and optimizes thedistribution of MgO in alloy. The preliminary investigation of Ag-Mg-Ni-Re indicates that the Y2O3and CeO2produce strengthening effect and decrease the elongation percentage. In comparison, Ceelement shows better strengthening effect.