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V. Babu,Balasivanandha Prabu Shanmugavel,K. A. Padmanabhan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8
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.
V. Babu,Balasivanandha Prabu Shanmugavel,K. A. Padmanabhan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
The influence of the semi-die angle (α = 45°, 30° and 22.5°employed in the present experiments) of the cyclic expansion extrusion (CEE) process on grain refinement in Al-alloy AA 6063 processed at 100°C at a pressing velocity of 0.5 mm.s− 1 and subjected to different number of passes is examined. The strain imparted on the specimen strongly depends on the die geometry. Grain refinement as well as increase in the ultimate tensile strength and micro-hardness after 10 CEE passes is the highest when the semi-die angle (α) is 22.5°. TEM images reveal the formation of fine grains after 10 CEE passes. Dislocation generation and cell formation directly depend on the strain imparted and the interactions between the dislocations and the Mg2Si precipitates. The tensile strength and hardness of the CEE processed specimens were compared as a function of the semi-die angle (α) and the results were compared with those of the unprocessed alloy also.