Prapas Kunnam
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Chaowalit Limmaneevichitr
材料科学技术（英文）
This paper presents the effects of different process parameters in producing Al-5Ti-1B grain refiner, i.e. various sequences and reaction time, on grain refinement efficiency of aluminum castings. It was found that different process parameters resulted in different morphology and size distribution of TiAl3 and TiB2 in grain refiner. The experiment was carried out by adding KBF4 and K2TiF6 to molten aluminum. The melting temperature was controlled at 800℃ in an electric resistance furnace. Three different sequences of KBF4 and K2TiF6 additions were applied, i.e., adding KBF4 before K2TiF6, adding K2TiF4 before KBF4 and mixing both KBF4 and K2TiF6 before adding to molten aluminum. Three different holding time at 1 min, 30 min and 60 min were applied. The results showed that no significant difference of morphology and size distribution was found by varying three different sequences. Whereas, the different holding time provided major differences in both morphology and size distribution, which are technically expectable from diffusion and agglomeration between particles resulting in larger particle size and wider range of size distribution of TiAl3 and TiB2. If the reaction time was longer than 30 min, morphology of both TiAl3 and TiB2 became too large. If the reaction time was too short, less reaction between TiAl3 and TiB2 to form would be obtained. For grain refinement efficiency, it was found that mixing KBF4 and K2TiF6 before adding to molten aluminum with a holding time of 30 min resulted in best grain refinement efficiency.
关键词:
Grain refinement
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Wattanachai Prukkanon
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Satit Chanpum
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Chaowalit Limmaneevichitr
材料科学技术（英文）
The effect of Sc on precipitation hardening of AlSi6Mg was studied. Zr was previously reported that it increased the effectiveness of Sc in wrought aluminum in many areas so Zr was also used together with Sc in this study. Different levels of Sc and Zr additions were added to AlSi6Mg before casting in the permanent mold. The samples were precipitation hardened at different aging temperatures and for various aging time before testing for tensile strength and hardness. It was found that Sc addition into Al6SiMg can change its response to age hardening. Additions of Sc and Sc with Zr increased both yield strength and hardness for both aging temperatures. In addition, Sc was found to modify eutectic Si to obtain fibrous morphology. This effect of Sc on eutectic silicon modification has never been reported before.
关键词:
Scandium
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