Relationship between Microstructure and Exfoliation Corrosion in Mg-14mass%Li-3mass%Al Cold-Rolled Alloy

Relationship between microstructure and exfoliation corrosion in Mg-14mass%Li-3mass%Al cold rolled material were investigated by controlling microstructure using heat treatment. The exfoliation corrosion was exhibited on the specimens with elongated microstructure by cold-rolling. Heat treatment at 200 degrees C only recovery occurred. Recovery and recrystallization were caused by heat treatment at 300 degrees C However, heat treated at 300 degrees C decreased precipitate fraction. Corrosion rate of heat-treated at 200 degrees C decreased by release the residual strain. However, heat treatment at 300 degrees C has lower corrosion resistance than heat-treated at 200 degrees C because it has less precipitate density than as-rolled. Exfoliation corrosion was shown in as-rolled and heat-treated at 200 degrees C. In as-rolled exfoliation corrosion was shown more significant when reduction rate increase. In as-rolled, exfoliation corrosion was shown more significant than heat-treated at 200 degrees C. After heat treatment to change the grain shape from elongated to equiatial, exfoliation was suppressed by the distribution of AlLi phase.