Korean Institute of Surface Engineering

pISSN : 1225-8024 | eISSN : 3399-8403


공학

한국표면공학회지 (41권3호 109-113)

Stress Corrosion Cracking of High Strength Al-Zn-Mg-Cu Aluminum Alloy with Different Compositions

고강도 Al-Zn-Mg-Cu 합금에서 조성에 따른 응력부식균열 특성

김준탁;김상호;
Kim, Jun-Tak;Kim, Sang-Ho;

한국기술교육대학교 신소재공학과;
Dept. of Materials Engineering, Korea University of Technology and Education;

DOI : 10.5695/JKISE.2008.41.3.109

Abstract

High strength 7xxx series Al-Zn-Mg alloy have been investigated for using light weight automotive parts especially for bump back beam. The composition of commercial 7xxx aluminum has the Zn/Mg ratio about 3 and Cu over 2 wt%, but this composition isn`t adequate for appling to automotive bump back beam due to its high resistance to extrusion and bad weldability. In this study the Zn/Mg ratio was increased for better extrusion and Cu content was reduced for better welding. With this new composition we investigated the effect of composition on the resistivity against stress corrosion cracking. As the Zn/Mg ratio is increased fracture energy obtained by slow strain rate test was decreased, which means degradation of SCC resistance. While the fracture energy was increased with Cu contents although it is below 1%, which means improvement of SCC resistance. These effects of composition change on the SCC resistivity were identified by observing the fracture surface and crack propagation.

Keywords

Stress corrosion cracking;Slow strain rate test;Zn/Mg ratio;Cu content;7xxx aluminium alloy;