Oxidation Resistance of Nanocrystalline Cu-Si Alloys at High Temperatures

The oxidation resistance of two nanocrystalline Cu-Si alloys with different grain sizes prepared by conventional casting (CA) and mechanical alloying (MA) techniques were studied by the thermo-gravimetric method at 700 ℃ and 800 ℃ in 105 Pa flowing pure O2 for 24 h.The results showed that not all kinetic curves for the oxidation of the alloys obeyed the parabolic law,and some curves exhibited abnormal oxidation behavior,but on the whole the mass gained from oxidation of MA alloys was smaller than that of the CA alloys.The continuous layers of SiO2 were not formed,the oxidation scales contained mixed oxides of Cu2O+SiO2 rich in SiO2 acting as barriers to restrain further diffusion of copper and oxygen.The reduction of grain size could increase the diffusion rate of the reactive component Si,accelerate the formation of SiO2 and mixed oxides of Cu2O+SiO2 rich in SiO2,and improve the high temperature oxidation resistance of Cu-Si alloys.