Stress corrosion cracking behaviors of RE-containing ME21 magnesium alloy processed by equal-channel angular pressing

A commercial as-cast ME21 magnesium alloy containing rare-earth (RE) element was processed by equal-channel angular pressing to obtain fine-grained microstructure. Stress corrosion cracking (SCC) behaviors of the fine-grained samples were studied by slow-strain-rate testing in air, distilled water and Hanks' solution at the strain rate of 1 × 10^?6 s^?1. All samples show a relatively low SCC sensitivity in distilled water but a great SCC tendency in Hanks' solution. The microscopic observations of the fracture surfaces and the side surfaces reveal obvious active anodic dissolution and hydrogen embrittlement cracks, which indicate the higher SCC susceptibility in Hanks' solution. The fine-grained microstructure with more crystal defects promotes the passivation process of the oxide film and restrains the hydrogen induced cracking of the ME21 magnesium alloy, leading to the higher general corrosion resistance as well as SCC resistance.