1100 commercial purity aluminum and ultralow carbon IF steel were severely deformed by the accumulative roll-bonding (ARB) process. The ARB processed specimens revealed the pancake shaped ultrafine grains whose mean grain thickness is about 200-400nm. The subsequent annealing treatment could produce the specimens having various mean grain sizes ranging from 200 nm to 15 mum, and systematic mechanical testing was carried out by the use of them. The strength of the both materials held Hall-Petch relationship in the present range of grain size, while the ultrafine grained materials performed limited uniform elongation due to early plastic instability. The fatigue strength of the aluminum increased with decreasing the grains size. Interestingly, the slope of the S-N curves significantly increased as the grain size decreased. The ductile-brittle transition temperature (DBTT) in the IF steel greatly decreased with decreasing the grain size, and the specimens having the grain sizes smaller than 5 mum did not show any brittle fracture surfaces even at -190 degreesC.