The Composition Design Of Oxidation-resistant Cu Alloy Based On The Stable Solid Solution Cluster Model

Copper based material has a profound application prospect due to its excellent electric and thermal conductivity. But the working environment of the copper based material is becoming increasingly harsh with the expansion of application. The copper is easily to be oxidized at high temperature in the air, which may result in device failures. In order to resolve this problem, the method of adding alloying elements into copper has been widely researched, by which a protective oxidation layer would form on the surface of the alloys. A number of effective antioxidant alloying elements had been explored, such as Al, Cr, Si. However, it’s difficult to determine a proper amount of the alloying elements to reach the best oxidation resistance effect in practical application. Therefore, a reasonable theory is needed to direct the composition design of oxidation resistant Cu alloy.According to the cluster-plus-glue-atom model, a series of Cu alloy compositions were designed based on the (Cu-Cu12)-Cu1,3pr5structure and were divided into two kinds. One was (Cu-Cu12)-[M1/13Ni112/13]5type, in which the connecting atoms of (Cu-Cu12)-Cu5was replaced by [M1Ni12] cluster, M could be replaced by Si,Cr,Fe. The other one contained a direct replacement of connecting atoms or the central atom in the basic clusters (Cu-Cu12-) by Al or Si. The solid solution and precipitation of the alloying elements in Cu matrix as well as the oxidation behavior and mechanism were explored. The main conclusions have been summarized as follows:(1) For the Cu-Cu12-[Ni12/12+xMx/12+x]5type alloys, the precipitation and solid solution of alloying elements could be controlled through adjusting the proportion of Ni and M. When M was replaced by Si, Ni2Si precipitated out in matrix on the basis of a small amount of solid solution, which could improve the oxidation resistance of the alloy obviously. When M was replaced by Cr, a continuous protective Cr oxide layer would form on the alloys with an appropriate proportion of Ni/Cr at isothermal process, which would obviously restrain inter-diffusion between O and metals. Under the non-isothermal conditions, the addition of Ni-Cr restrained medium temperature oxidation of the alloys below800℃obviously. Due to the spalling of oxidation layer resulting from the stress, a proper proportion of Ni/Cr was needed in both two experiments. When Cr and Fe replaced M together in equal proportion, the alloys all showed unsatisfactory oxidation resistance in both non-isothermal and isothermal conditions. The main reason was that the fourth constituent element Fe could not be oxidized preferentially to form protective oxidation films compared with Cr,which showed the importance of the third constituent element further.(2) The Cu-Al-Si type alloys showed complete solid solution state, which was corresponding with the composition design idca.AbO? type protective oxide Him could form on the surface of the alloy, which could also obviously inhibit the inter-diffusion between () and metals. It was found thai Si could improve the oxidation resistance of the copper by reducing activity of the matrix (Cu has negative enthalpies of mixing with Si).