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Kateryna Svynarenko,Yubo Zhang,Jinchuan Jie,Valentyna Kutsova,Tingju Li 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5
Al-5Ti-0.2C, Al-0.8Ti-0.2C, Al-8Ti-2C, and Al-10Ti master alloys were prepared and used to investigate theinfluence of excess Ti on the growth of TiC particles and its ability to nucleate Al-grains. The results of a microstructureanalysis of TiC-containing alloys and refined CPAl were interrelated to the results of a refinement test. Itwas found that the presence of excess Ti is essential at the stage of master alloy preparation, as it facilitates thegrowth and uniform distribution of TiC within the structure. In Al-5Ti-0.2C alloy containing excess Ti, carbideparticles grow faster and to a higher extent (from 0.29 μm to 0.44 μm) compared to Al-0.8Ti-0.2C alloy producedwithout excess Ti (from 0.29 μm to 0.32 μm). The results support the “Ti-transition zone theory” as the mechanismof grain refinement by TiC-containing master alloys. The refinement performance of Al-5Ti-0.2C is superiorcompared to the one achieved by adding Al-8Ti-2C and Al-10Ti master alloys in corresponding concentrations. For the TiC particles to become favourable nucleating sites, they must undergo certain interaction with excess Ti atthe stage of master alloy preparation.
Kateryna Svynarenko,Yubo Zhang,Jinchuan Jie,Valentyna Kutsova,Tingju Li 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.4
When Al-Ti-C master alloys are produced via the conventional Self-propagating High-temperature Synthesis(SHS), the reduction of production temperature below 1523 K leads to the drastic deterioration of the refiner efficacy. In the present work, a simple yet effective way to improve the combustion process for low TiC-containingrefiners is proposed. The SHS reaction was performed to obtain Al-10TiC slurry first, which subsequently wasmixed with Al-Ti melt to obtain Al-5Ti-0.2C master alloy. By means of the proposed method, the process temperaturewas lowered to 1323 K. According to the results, in the case of improved SHS approach, the Al temperatureafter the onset of reaction increases by 90-100 K more than in the case of conventional preparation route,providing better kinetic conditions for TiC formation. As a result, at 1323 K production temperature, the averagecarbide size increases by 100% as compared to the conventionally produced refiner, which is claimed to be a reasonfor the improved refining performance of master alloy.