On the Influence of Temperature and Number of Passes on the Mechanical Properties of an Al–Mg Alloy Processed by Cyclic Expansion Extrusion

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 at 200 °C, 300 °C and 400 °C. The average grain size of the starting annealed material was 84.5 ± 6.8 μm, with 39.4% being of the high-angle grain boundaries (HAGBs) type. After 8 CEE passes at 200 °C the material had an average grain size of 3.3 ± 0.6 μm and 41.3% of the grain boundaries were of the high-angle type (HAGBs). The combined effect of an increase in dislocation density and reduction in grain size as a result of CEE processing contributed to an increase in hardness and strength of the alloy. At 200 °C, the specimen exhibited uniform hardness values with a maximum improvement of 104% after 8 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.