Effect of the particle size on the thermal stability of nanostructured aluminum powder: dislocation density and second-phase particles controlling the grain growth

Simultaneous improvement in the strength and corrosion resistance of Al via high-energy ball milling and Cr alloying

“…Oxygen could also be present due to the fine oxide layer on the starting powder particles and incorporation of oxygen during HEBM and SPS. Such dispersoids are reported in previous studies [31][32][33].…”

Defects in nanomaterials processed by powder metallurgy

“…For instance, in the case of a 99.8% purity Al powder milled in liquid nitrogen at a temperature of ~70 K for 25 h (cryomilling), the particle size spans between a few tens of micrometres and 150 µm while the crystallite sizes are only between 30 nm and 120 nm [11]. The grain size determined by transmission electron microscopy (TEM) and the crystallite size obtained by x-ray line profi le analysis are in good agreement.…”

“…For cryomilled Al powders, the most probable impurity is nitrogen. It may segregate at grain boundaries as solute clusters, and also may cause precipitation of AlN nanoparticles, if the powder is heated up to high temperatures [11]. Additionally, the alumina and aluminium-hydroxide phases on the surface of Al particles may break during milling and be incorporated by the severely deformed Al particles.…”

“…Both the solute impurities and the secondary phase dispersoids hinder the annihilation processes of lattice defects. Since a fi ner particle has a larger specifi c surface area, both the surface alumina fraction and the nitrogen concentration migrating through the surface are larger, which yield higher dislocation density and smaller crystallite size inside the particle [11].…”

Thermal Stability and Microstructure of Nanometric 2024 Aluminum Alloy Powder Obtained by Cryogenic Milling and Spark Plasma Sintering

“…From the micromechanical point of view, it can be assumed that the movement of a grain boundary is due to the driving stress τ1 resulting from the driving force of grain growth, which is opposed by the resistance stress τ2 which is the drag force induced by defects in the deformed regions; grain growth can occur if τ1 is higher than τ2 33 . The driving stress is expressed by equation (3) 9 .…”