Effect of heat treatments on the tensile strength and SCC-resistance of AA7050 in an alkaline saline solution

Jing Chie Lin, Hsueh Lung Liao, Wern Dare Jehng, Chih Horng Chang, Sheng Long Lee

Research output: Contribution to journalArticlepeer-review

145 Scopus citations

Abstract

Effect of heat treatments (namely T6, T73, RRA, OP1 and OP2) on the tensile strength (TS) and stress corrosion cracking (SCC) resistance of aluminum alloy 7050 in 3.5% NaCl solution at pH 12 has been investigated using constant extension rate tester (CERT). T6 increases the TS but decreases the SCC-resistance. To the opposite, T73 (i.e., T6 + 160 °C/30 h) increases the SCC-resistance but decreases the TS. Retrogression and re-aging (RRA, i.e., T6 + 200 °C/10 min + water quench + 120 °C/24 h) increases both TS and SCC-resistance but this treatment confines only to thin and small specimens. Step-quench aging (SQA, i.e., 470 °C/1 h + step-quench to 200 °C/1 min + water quench/or air cooling + natural aging at room temperature/1 week + 120 °C/24 h) provides a relatively practical treatment to enhance both the TS and SCC-resistance even the specimen either having quenched in water (OP1) or cooled in the air (OP2) in the process. Through electrochemical testing and micro-structural examination, we found that both the TS and SCC-resistance of AA7050 is governed by the microstructures that depend on heat treatments.

Original languageEnglish
Pages (from-to)3139-3156
Number of pages18
JournalCorrosion Science
Volume48
Issue number10
DOIs
StatePublished - Oct 2006

Keywords

  • AA7050
  • CERT
  • Heat treatment
  • Mechanical strength
  • SCC-resistance

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