Stress corrosion cracking susceptibility of a high strength Mg-7%Gd-5%Y-1%Nd-0.5%Zr alloy

Abstract

Through performing the tensile tests with different strain rates in 3.5 wt.% NaCl solution, the stress corrosion cracking (SCC) behavior and the effect of strain rate on the SCC susceptibility of an extruded Mg-7%Gd-5%Y-1%Nd-0.5%Zr (EW75) alloy have been investigated. Results demonstrate that the alloy is susceptible to SCC when the strain rate is lower than 5 × 10−6 s−1. At the strain rate of 1 × 10−6 s−1, the SCC susceptibility index (ISCC) is 0.96 and the elongation-to-failure (εf) is only 0.11%. Fractography indicates that the brittle quasi-cleavage feature is very obvious and become more pronounced with decreasing the strain rate. Further analysis confirms that the cracking mode is predominantly transgranular, but the partial intergranular cracking at some localized area can also occur. Meanwhile, it seems that the crack propagation path is unrelated to the existing phase particles.

Keywords

• Magnesium alloy
• Stress corrosion cracking
• Strain rate
• Pitting corrosion