Stress corrosion cracking behavior of magnesium alloys EV31A and AZ91E

The stress corrosion cracking of the sand cast magnesium alloys, Elektron 21 (ASTM-EV31A) and AZ91E, was studied using compact tension specimens in distilled water and in Mg(OH)2 saturated 0.1 M NaCl solution under constant load. EV31A showed a higher KISCC than AZ91E, but exhibited a higher stage II crack growth rate than the latter. Fractography showed transgranular cracking for AZ91E and EV31A in distilled water, whereas mixed intergranular and transgranular cracking was observed for EV31A in the chloride environment. The crack propagation involved hydrogen embrittlement.