Stress corrosion cracking of a recent rare-earth containing magnesium alloy, EV31A, and a common Al-containing alloy, AZ91E

Stress corrosion cracking of the magnesium alloy Elektron 21 (ASTM–EV31A) and AZ91E was studied using constant load test in 0.1 M NaCl solution (saturated with Mg(OH)2), and slow strain rate test using glycerol, distilled water and Mg(OH)2 saturated, 0.01 M and 0.1 M NaCl solutions. Slow strain rate test indicated that EV31A was less susceptible to stress corrosion cracking than AZ91E. Under less intense loading of constant load, EV31A was found to be resistant to stress corrosion cracking. Fractography of EV31A specimens showed little evidence of hydrogen embrittlement. The superior resistance of EV31A is attributed to a more robust oxide/hydroxide layer.

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► Alloy EV31A and AZ91E were studied using SSRT and constant load techniques.
► Alloy EV31A showed higher resistance to SCC than alloy AZ91E.
► Crack initiation occurred from corrosion pits.
► Alloy AZ91E exhibited σSCC as 60% of the σYS in 0.1 M NaCl solution under CLT.
► The SCC resistance of EV31A is attributed to a protective film formed.