Unusual oxidation behaviour of Zr50Cu50 alloy at high temperatures

The oxidation of Zr50Cu50 alloy at 500-700 °C is characterized by preferential oxidation of zirconium, while the excess of copper is accumulated at the alloy-oxide interface forming the Zr14Cu51 phase. The strong reaction at 800 and 850 °C resulted in the total corrosion of the specimens in 21 and 15 h, respectively. The oxidation at elevated temperatures showed an anomalous decrease of the oxygen consumption rate in the temperature range 930-1000 °C, corresponding to the preferentially oriented crystallites of ZrO2 in the oxide scale at 900 and 1000 °C. The oxide layer consists of ZrO2 and CuO in the whole temperature interval of the oxidation. The reaction kinetics obeys a parabolic rate law. An activation energy of 92.0 ± 0.3 kJ/mol has been estimated.