Phase (matter)

Transmission electron microscopy

Intergranular fracture

Metallurgy

Materials science

Chromatography

Ultimate tensile strength

Precipitation

Metallography

Grain boundary

Precipitation hardening

Physics

Nanotechnology

Organic chemistry

Intergranular corrosion

Microstructure

Composite material

Analytical Chemistry (journal)

Atom probe

Chemistry

Scanning electron microscope

Meteorology

Journal of Material Science and Technology

The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150 °C have been investigated by using tensile tests, optical metallography, scanning electron microscopy, transmission electron microscopy and atom probe tomography analyses. With increasing Zn/Mg ratios, the ageing process is significantly accelerated and the time to peak ageing is reduced. T′ phase predominates in alloys of lower Zn/Mg ratios while η′ phase predominates in alloys with a Zn/Mg ratio over 2.86. Co-existence of T′ phase and η′ phase with a large number density is beneficial to the high strength of alloys. Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture. A strength model has been established to predict the co-strengthening effect of T′ phase and η′ phase in Al-Zn-Mg-Cu alloys, including the factors of the grain boundary, solid solution and precipitation.

Investigation on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys with various Zn/Mg ratios