Real time RBS study of Cu–Sn alloy thermal oxidation by means of a 4He 2+ external micro-beam

Abstract

An open-air furnace has been designed to study in real time the high-temperature surface transformation of materials by Rutherford backscattering spectrometry (RBS) in external beam mode. A device previously designed for the observation of the high-temperature oxidation of galena has been re-designed in order to analyse massive samples and to reach a temperature range up to 700 °C and a better temperature regulation (±2 °C). Experiments are carried out to measure, by RBS using a 3 MeV 4He 2+ external micro-beam, the dynamic growth of oxide layers in air on the surface of copper–tin alloys heated at temperatures varying from 250 to 650 °C. The results obtained demonstrate the usefulness of this approach: actually one single measurement series permits to obtain at the same time the composition of oxide layers built on the metal and their growth kinetic laws. In the particular study of bronzes, the growth kinetics obtained by this method show the large influence of tin concentration on the oxidation mechanism. These results are verified by measurements on samples oxidised in an independent closed furnace. The results show also the occurrence of different oxidation mechanisms as a function of temperature. A diffusion mechanism governs the oxidation kinetics only at some temperatures.