Abstract
The effect of cold rolling, which set 20% to 40% area reduction along the crack propagation direction, on the Charpy impact properties of a medium strength aluminum alloy (5083) was established by utilizing instrumented Charpy impact tests at temperatures ranging from 77K to 473K for four kinds of specimens which were cut out from a rolled plate in the directions parallel and vertical to the rolling direction. A standard V-notch was formed on the rolled surface of two specimens and in the vertical direction on the remaining two specimens.
In general, by cold rolling the absorbed energy decreased remarkably by about 30 to 60% as compared with that of the unrolled 5083-O specimen in the temperature range of 77K to 373K. It was found that the effect of cold rolling on the absorbed energy differed considerably depending upon the crack propagation direction. When the crack propagation direction was vertical to the rolled surface, an extraordinary increase of absorbed energy up to about 120% appeared at 77K as compared with that of the unrolled specimen. On the other hand, when the crack propagation direction was parallel to the rolled surface, the increase of absorbed energy was about 35 to 55% at 474K.
It is assumed that this extraordinary increase of absorbed energy at 77K is due to the occurrence of laminated fracture which was promoted by cold rolling.
