부산대학교 도서관

The influence of working temperature and number of passes on the mechanical properties of aluminium alloy, AA 5083,processed by cyclic expansion and extrusion (CEE) is discussed. The specimens were processed up-to 10 CEE passes at200 °C, 300 °C and 400 °C. The average grain size of the starting annealed material was 84.5 ± 6.8 μm, with 39.4% beingof the high-angle grain boundaries (HAGBs) type. After 8 CEE passes at 200 °C the material had an average grain size of3.3 ± 0.6 μm and 41.3% of the grain boundaries were of the high-angle type (HAGBs). The combined effect of an increasein dislocation density and reduction in grain size as a result of CEE processing contributed to an increase in hardness andstrength of the alloy. At 200 °C, the specimen exhibited uniform hardness values with a maximum improvement of 104% after8 passes and the ultimate tensile strength had also increased by 64% compared with the unprocessed condition. However,the mechanical properties decreased in the specimens that were processed at the higher temperatures of 300 °C and 400 °C.