Effects of Sc and Zr microalloying additions and aging time at 120 °C on the corrosion behaviour of an Al-Zn-Mg alloy

Sc and Zr microalloying additions and increasing aging time at 120 degrees C both can effectively improve the corrosion resistance of Al-Zn-Mg alloys. The low corrosion susceptibility caused by adding Sc and Zr is from refining grains and restraining the formation of precipitate free zone. The improved corrosion resistance from prolonging aging time at 120 degrees C is due to the coarsening of matrix and grain boundary precipitates, and the increased spacing of grain boundary precipitates. Aged at 120 degrees C for 36 h, the Al-Zn-Mg alloy microalloyed with 0.25 wt.% Sc and 0.10 wt.% Zr exhibits high mechanical properties and admirable corrosion resistance. (C) 2012 Elsevier Ltd. All rights reserved.