Aging behavior of Ultra-Fine Grained Al-0.5%Si-0.5%Ge Alloy Fabricated  by ARB Process

Keiyu Nakagawa, Nobuhiro Tsuji, Daisuke Terada, Toshihiko Nakano, Khairul Nizam and Teruto Kanadani

ultrafine grain､sever plastic deformation, alumunum-silicon-grumanium alloy, aging-hardening
The aging behavior of ultrafine-grained (UFGed) Al-0.5%Si-0.5%Ge alloy fabricated using six-cycle accumulative roll-bonding (ARB) processing has been investigated using Vickers hardness measurement and TEM observation.
The hardness of UFGed alloy before aging is about 2.3 times higher than that of the starting specimen without ARB process. The starting UFG specimen showed ultrafine grains with mean size of 156 nm. The hardness of a UFG specimen aged at 473 K decreased monotonously with increasing aging time. From TEM observations of the microstructure of UFG specimen aged after long-term aging at 473 K, results show that the mean size of ultrafine grains increased significantly with increasing aging time.　Furthermore, few precipitates exist inside gains, although many coarse precipitates exist at grain boundaries. The hardness of UFG specimen aged at 373 K showed higher value than that aged at 473K. From TEM observations, results showed many elongated ultrafine grains, with many precipitates formed on the grain boundaries and inside grains of the specimens aged at 373 K. 
These results suggest that precipitation hardening strongly affected the hardness in this alloy because it has many elongated ultrafine grains. Many fine Si-Ge precipitates formed inside grains of the UFG specimen aged at 373 K in long-term aging.


Aging behavior of Ultra-Fine Grained Al-0.5%Si-0.5%Ge Alloy Fabricated  by ARB Process

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