Effect of grain size on hydrogen embrittlement properties of 6061 aluminum alloys

Abstract

For 6061-T6 aluminum alloy plates with fine- or coarse-grained structure, SSRT (slow strain-rate technique) in humid air was carried out using a smooth or notched tensile specimen to evaluate the susceptibility to hydrogen embrittlement and to demonstrate the hydrogen effect on fracture process. The fine-grained materials under the hydrogen environment showed little change in tensile properties compared with the inert environment of dry nitrogen gas, while the coarse-grained materials exhibited some change in ductility; namely a decrease for the smooth specimen and an increase for the notched specimen. Although the materials ruptured by ductile fracture independently of grain size, the characteristic feature that coarse slips and void formation were promoted by hydrogen was observed. It is therefore suggested that the nature of hydrogen effect in 6061-T6 alloys is an enhancement of ductile fracture. As the increase in grain size leads to encourage the hydrogen effect, the grain coarsening should be restrained.