Effects of Si addition on the oxidation behavior of a Cu-Zr-based bulk metallic alloy

The effect of Si addition on the oxidation of (Cu(43)Zr(43)Al(7)Ag(7))(99.5)Si(0.5) bulk metallic glass (CZ43S-BMG) was investigated over the temperature range of 375-500 degrees C in dry air. The results generally showed that the oxidation rates of the CZ43S-BMG followed a multi-stage parabolic-rate law, and the oxidation rate constants (k(p) values) fluctuated with increasing temperature. It was found that the k(p) values of the CZ43S-BMG were slightly slower than those of the Si-free glassy alloy (Cu(43)Zr(43)Al(7)Ag(7), named as CZ43-BMG). The scales formed on the CZ43S-BMG strongly depend on temperature, consisting of 3 different modifications of ZrO(2) and CuO, and minor amounts of Cu(2)O (formed at T >= 425 degrees C) and Al(2)O(3) (only detected at 500 degrees C). In addition, the glassy substrate remained amorphous nature at T <= 400 degrees C, while it transferred to the crystalline phases of Cu(10)Zr(7), ZrAl, and ZrSi(2) after the oxidation at higher temperatures. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.