| Due to the release of Cd steam which harms to environment and health, Ag-Cd O contact materials has been limited to use in electric industry. So, it’s urgent to find new materials to substitute for Ag-Cd O material. Binary Ag-Cu alloy is a traditional electrical contact material which gains widely use in electric industry. But the oxidant of Cu and poor anti electric arc resistance performance limit the application of traditional Ag-Cu contact material. Studies on silver based contact materials mainly focus on the 80 wt.%~95wt.% silver content which leads to the production of silver is limited and expensive. What’s more, China is a country with scarce silver resources. Internal oxidation method was introduced to low silver content of Ag-Cu alloy in this paper to obtain an optimized structure of internal oxidation composed of copper oxide particles, silver rich belt and matrix alloy what could improve their properties. The research about Ag-Cu O with low silver contact materials has a great theoretical and practical significance.In this paper, internal oxidation was used to prepare Ag-Cu O with low silver electrical contact materials. The research is mainly about the influence of the addition of Co and Si element to hypereutectic Ag-Cu alloy metamorphism study, metamorphic process to Ag-Cu alloy internal oxidation behavior, the mechanical and electrical properties study of internal oxidation Ag-Cu. The main research conclusions are as follows:1. The addition of Co or Si element alone has no modification effect to hypereutectic Ag-Cu alloy with a primary rich copper phase. Only Co/Si multi addition had obvious modification effect. For the hypoeutectic Ag- Cu alloy, Co and Si element multi addition has no modification effect. For Ag-50 wt.% Cu alloy, with the increase of Co content, the modification effect of primary copper phase is more obviously. When Co content is higher than 0.3wt.%, the grain size of primary copper phase increases slightly. The optimal content is 0.3wt.% Co +0.2wt.% Si.2. Cobalt silicon compounds act as propitious sites for the heterogenous nucleation of Cu phase. The silver rich phase around the copper rich phase prevent the further grow up of the primary copper phase and increases the constituent supercooling. The primary phase in alloy changes from dendritic crystal to spherical crystal.3. The relationship between the square of internal oxidized layer depth and oxidation time followed linear law. The rate of oxidation increases with the increasing of copper content. The oxidation rate of alloys with Co/Si multi addition are much lower than alloys without Co/Si multi additions.4. The internal oxides of alloy with Co/Si multi addition were composed of granular and lath-like copper oxides. In alloys without Co/Si multi addition lath-like copper internal oxide layers were founded. For Ag-50 wt.% Cu alloy, Co Si compound can effectively inhibit the growth of oxidative and lamination in the alloy. After internal oxidation, the surface of the alloys exhibited gradient structure with rich silver and the matrix with low silver.5. The hardness of alloys decreased with increasing of Cu content which mean the addition of Co and Si can improve the hardness. Compared with the internal oxide layer, the matrix has higher hardness. Compared with pure silver, Ag-Cu alloy after internal oxidation have higher resistivity. Surface region of surface layer has the higher resistivity, and deeper region has the lower resistivity because of the net-like structure of pure silver layer in this layer.6. Due to the gradient structure with rich silver surface, Ag-Cu hypereutectic alloy after internal oxidation presented better oxidation resistance at high temperature than alloy before oxidation. The internal oxide particles also improved anti-electric arc resistance performance of the alloy. |
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