Oxidation Of Cu-alloys At High Temperature

Copper (Cu), as a metal that was found early and now has a wide range of application, is gradually accepted as a replacement for other metals because of its lower resistivity and im proved electromigration resistance. Howerver, it is inevitable that oxidation happens while copper working in these circumstances. But, the oxides can not play a protective effect on copper, thus affecting components of working life and further limiting the application of copper. So, the basic, broad understanding of the metal and alloy oxidation behavior on the surface is so important to research and development and application.Since the 1930s, a great deal of research on high temperature oxidation of copper refers to unidentical results. Even in a certain temperature range, the oxidation not exactly the same. Two copper oxides cuprous oxide and copper oxide are not effective to prevent the oxidation of copper. Well, it is necessary to consider the addition of alloying elements the way, or changing the handling of the alloying element to increase capacity to high temperature oxidation resistance. Many researchers have studied the tim aluminum to copper, magnesium, nickel and other alloying elements to improve the performance of its high-temperature oxidation. But all of the results, even if the alloy is the same as the percentage of the same elements, the results are not entirely consistent, maybe for the oxidation and copper before the heat treatment. About 80% of the world copper containing Cu₂S from the smelting of copper. There are two main sources of the S in copper: left over from the smelting of copper containing Cu₂S; the process of the gases containing S in the use of copper alloy. And the S congeners elements Se, Te also can be combined with copper and diversify. in the course of the study of high temperature oxidation, many studies have found that elemental S, Se on the part of metal such as Ni, Fe, Cr and other metal alloys has high- greatly affect on temperature oxidation, which can speed up the corrosion. And other scholars believe that these elements can delay the high temperature corrosion of metal. Zhu etc found that 4N Cu and 6N Cu element of the differences between small, high-temperature oxidation rate are vastly different on the high-temperature oxidation of 2N Cu , 4N Cu and 6N Cu. It is concluded that mainly copper alloys contain the non-metallic trace element S, Se. The studis on the Cu-S, Cu-Se alloy at high temperature oxidation behavior are simple observations on content of the surface. It is roughly considered that oxide film forms in the process. However, how S or Se affect alloy oxidation rate and high temperature oxidation mechanism is not clear.These two elements are both non-metallic element in the same group, and vulnerable to the introduction of additional elements in the copper smelting process. So, It is necessary to carefully examine its copper oxide high-temperature impact.This paper first tests on Cu-S alloy at high temperature oxidation behavior, then compares the result to that of 6N Cu. From the perspective of kinetic curves, we found that 6N Cu oxidation rate was higher than that of Cu-S alloy . It is noted that, on the temperature of 300-500℃, adding alloying elements appropriate indeed enhances its antioxidant capacity. But, on 600-900℃, Cu-S alloy oxidation rate is no longer smaller than 6N Cu as low temperature, but increased significantly in this temperature range. In order to further understand the results of high-temperature alloys, different temperature oxidation of the surface morphology were observed . From the observation of the surface morphology, results consist what the basic dynamics of the curve show. After that, we analysis Cu-Se alloy made of high-temperature oxidation behavior, comparing with the results of Cu-S experimental results in previous chapter. From the observation of the surface morphology, the oxidation rate of Cu-Se, on 300-500℃, is also smaller than that of 6N Cu, and smaller than Cu-S too. It is shown that adding Se elements indeed enhances its antioxidant capacity. In the same way, in the relatively high temperature of 600-900℃, the oxidation rate of Cu-Se is higher than 6N Cu, but lower than Cu-S. It is shown that the antioxidant effect of Cu-Se alloys is not as 6 N Cu, but slightly better than in the Cu-S. In order to further understand the results of high-temperature alloys, different temperature oxidations of the surface and cross-section shape ware observed. From the results of observation, it is agrees with the outcome of the appeal.It is concluded as follows. Firstly, as low addition levels of alloying elements, oxidation kinetics shows parabolic law in latm ,on all temperatures; Secondly, oxidation alloy surface layer is mainly Cu₂O on lower temperatue while Cu₂O and CuO on the temperature higher than 500℃. Morever, on the temperature of 300-500℃, with the Increasing activation energy, the antioxidant capacity of low-temperature copper alloy improves , mainly due to its alloying elements and hinder the oxygen in the oxide layer as well as the proliferation of alloy. On 600-900℃, the activation energy values of the three are very close, while 6N Cu the highest. Pure metal oxide is mainly based on lattice diffusion. Add alloy elements are in the hope of integration into the Cu₂O in order to lower their lattice diffusion. But in fact it did not work.