CHARACTERIZATION OF AMORPHOUS ZR-CU ALLOY SURFACES BY ELECTRON-PROBE MICROANALYSIS AND AUGER-ELECTRON SPECTROSCOPY

The surfaces of an amorphous Zr-Cu alloys exposed to a laboratory air with the relative humidity of about 60+/-10% at room temperature were studied by Auger electron spectroscopy (AES) and scanning electron mic roscope equipped with an energy dispersive X-ray analyzer (SEM/EDX). I n general, the oxidation behavior of the roll-side of the specimen whi ch was in contact with the chilling wheel during quenching was differe nt from that of the freely solidified surface. AES analysis of the spe cimen surfaces kept in a desiccator for 23 months showed that the comp osition of the topmost region corresponded almost to ZrO2, although so me copper was also detected. Thickness of the surface film of ZrO2 in the corrosion resistant region was about 4-5 nm, while that on the rol l-side was smaller, especially in the region where a large amount of C u was detected. Under the surface film, a large enrichment of Cu was e stimated by non-destructive analysis of the AES data. The SEM/EDX obse rvation of the cross-sections heavily corroded specimens clarified tha t the corrosion products consists of several layers of Cu-rich layers and Zr-rich layers which appear alternately. It is speculated that a m etallic copper layer is formed under the surface film by preferential diffusion of Cu to the surface, which makes the ZrO2 layer unstable an d results to the break-down of the film.