Oxidation Behavior of Nanocrystalline Cu-Si Alloys Prepared by Mechanical Alloying

The oxidation of two Cu-Si alloys with different compositions prepared by conventional casting (CA) and mechanical alloying (MA) at 973 and 1073 K under 1 atm of flowing pure O-2 was conducted to investigate the influence of grain size on the high-temperature oxidation resistance of alloys by TGA, SEM and XRD. The results show that CA Cu-0.1Si alloy at both temperatures, MA alloy at 1073 K in previous 23 h, CA Cu-0.5Si alloy at 1073 K and MA Cu-0.5Si alloy at 973 K obey the parabolic law, and on the whole the mass gain of MA alloys is smaller than that of the corresponding CA alloys. The analysis of oxide scales shows that all alloys did not form continuous layers of SiO2 but formed complex and similar scales after oxidation, which involved layers composed of mixed oxides of Cu2O and SiO2 rich in SiO2 acting as barriers to restrain further diffusion of both copper and oxygen. The reduction in the alloy grain size speeds up the diffusion of the reactive component of Si, improves the volume fraction of SiO2 in the mixed oxides of Cu2O and SiO2, and improves the high-temperature oxidation resistance of Cu-Si alloys.