Role of trace nanoparticles in establishing fully optimized microstructure configuration of cold-rolled Al alloy.

[Display omitted] • Trace nanoparticles stimulated nuclei of α -Al and weakened the micro-segregation. • Nano-TiC-TiB 2 was more effective stimulating nucleation of α -Al. • Nano-TiC-TiB 2 was more effective in promoting and hindering recrystallization. • The nucleation rate of Al 2 Cu was increased by trace nanoparticles during aging. In this paper, we took cold-rolled Al-Cu 5.0 -Mg 0.5 -Si 0.5 alloy as the research object. The roles of 0.1 wt% in-situ nano-TiC and nano-TiC-TiB 2 in solid–liquid and solid-state transformations (solution plus aging precipitation) were systematically investigated and compared. We found that trace in-situ nanoparticles can stimulate the nucleation of α-Al dendrites and hinder their growth, meanwhile serving as the heat storage and heat sustained-release carriers during solid–liquid transformation. In the process of solid-state transformation, recrystallization nucleation is promoted, and grain boundaries are pinned by nanoparticles. Meanwhile, the nucleation of Al 2 Cu is accelerated, and refined Al 2 Cu distributes more uniformly. Besides, similarities and differences in the manipulation mechanisms of nano-TiC and nano-TiC-TiB 2 during solid–liquid and solid-state transformations were analyzed. The mechanical properties and the responsible strengthening mechanisms were discussed in detail. [ABSTRACT FROM AUTHOR]