Design of novel high-performance Al–Cu–Mg alloys containing Zn and Li

Abstract

To design novel high-performance aluminium alloys, the properties and microstructure of Al–4.2Cu–1.4Mg alloy containing Zn and Li have been investigated by tensile tests, fatigue crack propagation test, slow strain-rate tensile test, Kahn tear test, scanning electron micrography and transmission electron micrography. The stress corrosion cracking resistance and toughness of Al–4.2Cu–1.2Mg alloy can be markedly improved by small Zn addition. Independent Li addition has no significant effect on the corrosion resistance of Al–4.2Cu–1.2Mg alloy, but the tensile strength is improved and the fatigue crack propagation is restrained. Small Zn addition promotes the precipitation of S′ phase during age treatment, and the grain boundary precipitates are scarcer than those of the base alloy. The co-effect of Li and Zn addition promotes the fine and dispersed precipitation of the S′ (non-equilibrium Al₂CuMg) phases in Al–4.2Cu–1.2Mg alloy. The comprehensive performance (the fracture toughness, tensile properties, stress corrosion resistance and fatigue crack propagation resistance) of Al–4.2Cu–1.2Mg alloy with 0.25% Zn and 1.0%Li is outstanding. This alloy could lay the foundation for the design of new aluminium alloys.

Keywords

Aluminium alloy alloying damage tolerance corrosion resistance microstructure

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