Influence of minor combined addition of Cr and Pr on microstructure, mechanical properties and corrosion behaviors of an ultrahigh strength Al-Zn-Mg-Cu-Zr alloy

Ming Wang; Lanping Huang; Kanghua Chen; Wensheng Liu

doi:10.1016/j.micron.2017.10.008

Influence of minor combined addition of Cr and Pr on microstructure, mechanical properties and corrosion behaviors of an ultrahigh strength Al-Zn-Mg-Cu-Zr alloy

Micron. 2018 Jan:104:80-88. doi: 10.1016/j.micron.2017.10.008. Epub 2017 Oct 26.

Authors

Ming Wang¹, Lanping Huang², Kanghua Chen³, Wensheng Liu³

Affiliations

¹ State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China.
² State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Science and Technology on High Strength Structural Materials Laboratory, Central South University, Changsha 410083, China. Electronic address: christie@csu.edu.cn.
³ State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Science and Technology on High Strength Structural Materials Laboratory, Central South University, Changsha 410083, China.

PMID: 29112917
DOI: 10.1016/j.micron.2017.10.008

Abstract

This work focuses on controlling grain boundary structure in an ultra-high strength Al-8.6Zn-2.5Mg-2.2Cu-0.16Zr (wt.%) alloy by the combined addition of trace Cr (0.1wt.%) and Pr (0.14wt.%), and evaluating mechanical properties and localized corrosion behaviors of the alloy in the peak aged condition. The introduction of trace Cr and Pr leads to the formation of nanoscale Cr, Pr-containing Al₃Zr and Zr-containing PrCr₂Al₂₀ dispersoids which can obviously inhibit the recrystallization and sub-grain growth of the super-high strength Al-Zn-Mg-Cu alloys, and retain the deformation-recovery microstructure dominated by low-angle grain boundaries. The nearly ellipsoidal dispersoids with a size of 10-35nm are discretely distributed and precipitate free zones are hardly formed in low-angle grain boundaries. This new alloy composition exhibits better combined properties, higher resistance to stress corrosion, exfoliation corrosion and inter-granular corrosion with the undamaged strength, ductility and fracture toughness.

Keywords: Al-Zn-Mg-Cu alloys; Corrosion resistance; Low-angle grain boundary; Precipitates; Recrystallization; mechanical properties.