Precipitation behaviors and properties of solution-aging Al-Zn-Mg-Cu alloy refined with TiN nanoparticles

The precipitation hardening characteristics, aging precipitation behaviors, mechanical properties and electrical conductivity of the Al-Zn-Mg-Cu alloy refined with TiN nanoparticles (well supported by Ti microparticles) are investigated, in detail. The results show that, compared with the alloy with only Ti or without any refiner, the TiN nanoparticle addition improves the solution of the alloying elements, retains the fine grains of the Al-Zn-Mg-Cu alloy during the solid solution process and enhances the Vickers hardness of the solution treated alloy. More importantly, during the aging process, the TiN nanoparticle addition promotes the diffusely uniform precipitation of the G.P. zones, η′ phase and η phase, and accelerates the evolution to the G.P. zones from the supersaturated solid solution in the matrix, but inhibits the precipitations of η′ phase and η phase. The yield stress (569.8 MPa), ultimate tensile stress (595.5 MPa) and elongation (18.1%) of the alloy refined with TiN are higher than those with only Ti or without any refiner. In addition, the electrical conductivities of the aged alloy with TiN are lower than those of the alloy with only Ti or without any refiner.