Influence of Scandium Addition on Stress Corrosion Cracking Susceptibility of Al-Zn-Mg Alloy in Different Corrosive Environments

Abstract

Stress corrosion cracking (SCC) susceptibilities of Al-Zn-Mg alloys without and with Scandium addition were evaluated in 3.5% NaCl solution at different pH and different strain rate, using slow strain rate test technique. The results indicate that Sc addition reduces grain size and width of precipitation free zones, and transforms grain boundary precipitates from continuous distribution into interrupted distribution by inhibiting recrystallization. In solution at pH 1, pH 3 and pH 7, Sc addition reduces the degree of localized corrosion of alloy surface and SCC susceptibility of Al-Zn-Mg alloy. However, in solution at pH 10 and pH 12, grain refinement significantly promotes the diffusion of hydrogen atoms into matrix, thus Sc addition increases SCC susceptibility of Al-Zn-Mg alloy. Under different strain rate conditions, Sc addition can all reduce SCC susceptibility of Al-Zn-Mg alloy in solution at pH 1, pH 3 and pH 7, and can all increase SCC susceptibility of Al-Zn-Mg alloy in solution at pH 10 and pH 12. As a result, Sc modified Al-Zn-Mg alloy in practical applications should be avoided in alkaline environments.

Homogenization Modes Effect on Mechanical Properties and Corrosive Characteristics of the Rolled Products from Al-Mg (1570) Aluminum Alloy with Addition of Scandium and Zirconium

“…Due to their high cost, aluminum alloys with scandium are applied only in the space industry, existing researches of these alloys are focused on the study of physical and mechanical properties with a few studies addressing their behavior in aggressive media [1][2][3][4][5][6]. In case the use of rolled products from these alloys is considered for marine hull building or in structures in contact with sea water, corrosion resistance tests in this environment (for delamination and intergranular corrosion) should be carried out.…”