Nanotreating High-Zinc Al-Zn-Mg-Cu Alloy by TiC Nanoparticles

High-zinc Al-Zn-Mg-Cu alloys offer the highest strength among all aluminum alloys mostly due to high-volume precipitates after heat treatment. However, the high zinc content makes the alloys more sensitive to hot cracking and stress corrosion cracking during solidification and solid state processing. Recently, a revolutionary method, Nanotreating, becomes significant in metals processing by introducing ceramic nanoparticles into metals. It is an emerging method to modify the microstructures (both primary and secondary phases) during solidification, deformation and heat treatment. In this work, In situ TiC nanoparticles were added into Al-8.6Zn-2.8Mg-1.8Cu alloy to study the nanotreating effects. The grain size of the as-cast alloy has been reduced significantly from 272.3 mu m to about 30.4 mu m by 1 vol% TiC nanoparticles. The size of remaining large secondary phase after heat treatment were reduced significantly as well. Furthermore, the hardness was enhanced. Nanotreating is promising as an effective approach to modify the microstructure, relieve the manufacturing difficulty, and enhance the properties of the high-zinc Al-Zn-Mg-Cu alloys for widespread applications.