Influence of Planar Anisotropy on Stress Corrosion Cracking of Extruded AZ31 Magnesium Alloy Plate.

The stress corrosion cracking (SCC) behavior of an extruded AZ31 alloy plate with a large planar anisotropy was investigated using constant load test in 0.01 mol/l NaCl solution at 35°C. Due to the texture with a large spread of (0001) orientation in the transverse direction (TD), the extruded AZ31 alloy plate exhibited a much higher yield strength (169 vs. 70 MPa) along the extrusion direction (ED) compared with the TD. The threshold stress for SCC was slightly higher for the ED specimen compared with the TD specimen (90 vs. 70 MPa) due to the much higher yield strength. However, the ratio between threshold stress and yield strength was much larger for the TD specimen (100% vs. 53%), indicating its low susceptibility to SCC. Corrosion grooves formed perpendicular to the tensile direction and along the interstices of Mg(OH)2 corrosion product film. Corrosion grooves acting as fracture initiation sites tended to propagate along non-basal planes, particularly, prismatic plane, due to lower corrosion resistance compared with basal plane. The higher resistance to SCC for the TD specimen may be attributed to the higher probability of basal plane on the exposed surfaces of corrosion grooves. [ABSTRACT FROM AUTHOR]