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http://dx.doi.org/10.7777/jkfs.2011.31.6.347

The Effect of Ca Addition on the Grain Growth Inhibition During Reheating Process of Al-Zn-Mg Al Alloys for Thixo-extrusion  

Park, Hyung-Won (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Kim, Dae-Hwan (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Shim, Sung-Yong (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Kim, Hee-Kyung (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Seong, Bong-Hak (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Choi, Chang-Ock (Korea institute of Science and Technology Information, ReSEAT program)
Lim, Su-Gun (Gyeongsang National University, i-Cube Center, Engineering Research Institute)
Publication Information
Journal of Korea Foundry Society / v.31, no.6, 2011 , pp. 347-353 More about this Journal
Abstract
There is thixo-extrusion to form high strength aluminum alloy. But, it is a problem that grains become grain coarsening during reheating process because the alloy was exposed at high temperature. In order to solve grain growth during reheating process, calcium was added in Al-Zn-Mg alloys. Primary a grain sizes of semi-solid Al-Zn-Mg-(0, 0.4, 0.6 and 0.9, wt.%)Ca were measured with image analyzer after reheating. Measured primary a grain sizes were applied to LSW(Lifshitz-Slyozov and Wagner) equation to check the effect of Ca on grain coarsening. Coarsening rate constant K values of semi-solid Al-Zn-Mg-(0, 0.4, 0.6 and 0.9, wt.%)Ca alloys were $371\;mm^3s^{-1}$, $247\;mm^3s^{-1}$, $198\;mm^3s^{-1}$ and $166 mm^3s^{-1}$, respectively. As increasing calcium content, K value decreased which means grains are refined. Also, grains of calcium addition were more spherical than that of calcium free.
Keywords
Al-Mg-Zn alloy; Ca addition; Reheating; Thixo-extrusion;
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