The age-hardenings behavior and precipitate microstructures with high dislocation density and/or ultrafine grains have been studied for 6022Al-Mg-Si and 2091Al-Li-Cu alloys. The high-pressure torsion (HPT) specimen of the former alloy exhibited either suppressed age hardenings or even age softening, unlike in the cases of the undeformed and cold-rolled specimens, at room temperature (RT) to 443 K (170 C). On the other hand, the HPT specimen of the latter alloy successfully increased the hardness up to >HV290 at 373 K (100 C), suggesting that concurrent strengthening by ultrafine-grained and precipitation hardenings can be activated if both alloy system and aging temperature are optimally selected. The corresponding transmission electron microscopy (TEM) microstructures attributed such a high level of hardness to the transgranular precipitation of the nanometer-scale particles within ultrafine grains. From the results of in situ small-angle X-ray scattering (SAXS) measurements, methods to maximize the effect of the combined processing of severe plastic deformation (SPD) and the age-hardenings technique are proposed based on the underlying phase transformation mechanisms.
|ジャーナル||Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science|
|出版ステータス||Published - 2013 8月|
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