Effect of storage on the stability of the grained structure and phase transformations in the nanocrystalline alloy 1450 doped with Sc and Mg

Multicomponent Aging Al-Li-Based Alloys of the Latest Generation: Structural and Phase Transformations, Treatments, Properties, and Future Prospects

“…Properties of a highly deformed alloy after low-temperature annealing and storage. Measurements of the mechanical properties (MP) of the annealed alloy after its storage showed that they (MP) retained their stability for a long (at least 1.5 year) storage at room temperature, which is in good agreement with structural studies that revealed the dimensional (size) stability of the recrystallized NC structure, the preservation of the degree of the dispersion, the character and density of the distribution of the hardening equilibrium phases that had precipitated during annealing at artificial aging [143].…”

“…The formation of grain boundary dislocations in the form of flat walls or dipoles is quite reasonable, since they are the most stable dislocation configurations in highly nonequilibrium nanocrystalline materials [140,145,146]. In the most alloyed alloy 1450, structural changes proceeded more slowly [143,144]; however, even in this case, after 1.5 years of storage, the formed NC and SMC grains were visualized on the microstructure images. It should be particularly noted that in the samples of the alloy 1450 deformed by the smallest number of revolutions n = 0.25, the initial misoriented cellular substructure also turned into a mixed NC + SMC grain structure.…”

Acceleration of volume decomposition of supersaturated Al + 4 wt.% Cu solid solution under irradiation with Ar+ ions

“…It is shown in Refs. that the storage (natural aging) of the 1450 alloy (Al–Cu–Li–Zr–Mg–Sc), which was deformed by high pressure torsion, from 1 month to 1.5 years as well as its artificial aging at 150 °C for 15 h results in the formation of stable fine Т 2 (Al 6 CuLi 3 ) and S 1 (Al 2 LiMg) phases (instead of metastable δ ′ and θ ′ phases formed under the same aging conditions in the alloy with a conventional microcrystalline structure). Along with heterogeneous nucleation at nanograin boundaries , the internal mechanisms of their nucleation and growth from a supersaturated (not only with substitutional impurities, but also vacancies) solid solution into the grain volume intensify with increasing aging time.…”

“…A particularly good example of the above is accelerating solid solution decomposition in alloys subjected to severe plastic deformation (SPD). SPD activates the decomposition and changes its stagewise character as indicated in a number of papers [27][28][29][30][31][32][33][34][35].…”

“…Thus, SPD changes the mechanism and kinetics of the supersaturated solid solution decomposition in quenched aluminum alloys and causes the formation of fine stablephase particles which appear in the alloys not subjected to SPD, usually only at high-temperature annealing. This SPD effect is due to an increase in the density of interfaces (nanograin boundaries) and lattice defects (dislocations and vacancies) [29][30][31][32][33][34][35].…”