Grain refinement of commercial EC Grade 1070 Aluminum alloy for electrical application
Master thesis
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http://hdl.handle.net/11250/2615778Utgivelsesdato
2014Metadata
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Sammendrag
The aluminium alloys for electrical conductivity applications are not grain refined since the addition of grain refiners might decrease their electrical conductivity by inserting impurities into the melt. Still, non-grain refined aluminium may lead to bar fracture and cracks during metalworking for making wire rods.The present study focuses to find an optimum balance between the grain refiner addition and the electrical conductivity of commercial EC grade 1070 aluminium alloy for electrical application. In order to reach this goal, the electrical conductivity and the macrostructure of commercial EC grade 1070 aluminium (commercial pure aluminium) have been studied under a series of controlled lab scale trails. Specific addition levels of different grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and samples were taken at specific time intervals. The collected samples were sectioned, ground and macro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera and the electrical conductivity measured by AutoSigma 3000 (EC meter) at room temperature. The obtained result was expressed as a percentage of the International Annealed Copper Standard (IACS %). The macro-structural analysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of 0.1%, cannot grin refine commercial pure aluminium. However, by increasing the grain refiner addition level the number of columnar grains increased and the size of decreased.The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the other grain refiners (up to 0.1%), showed significantly better grain refining performance. By the addition of 0.1% of this grain refiner the macrostructure became very fine equiaxed already after 30 minutes. The fading of the Al-3Ti-0.15 master alloy was, however, observed for samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a 90 minutes holding time the macrostructure remained as equiaxed grains.The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreased the electrical conductivity of commercial pure aluminium.