Macrosegregation Formation in an Al–Si Casting Sample with Cross-sectional Change During Directional Solidification
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In: Transactions of the Indian Institute of Metals, Vol. 71.2018, No. 11, 06.10.2018, p. 2639–2643.
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TY - JOUR
T1 - Macrosegregation Formation in an Al–Si Casting Sample with Cross-sectional Change During Directional Solidification
AU - Zhang, Haijie
AU - Wu, Menghuai
AU - Zheng, Yongjian
AU - Ludwig, Andreas
AU - Kharicha, Abdellah
PY - 2018/10/6
Y1 - 2018/10/6
N2 - A unidirectional solidification experiment of hypoeutectic Al-7.0 wt% Si alloy against gravity direction in a cylindrical mold with cross-sectional change was made, and the macrosegregation in different parts of the as-solidified sample was investigated (Ghods et al. in J Cryst Growth 441:107–116, 2016; J Cryst Growth 449:134–147, 2016). The current study is to use a two-phase columnar solidification model to analyze the segregation mechanisms as used in this experiment. Following flow phenomena and their contributions to the formation of macrosegregation are simulated and compared: (1) solidification shrinkage-induced feeding flow; (2) thermo-solutal convection; and (3) combined thermo-solutal convection and shrinkage-induced feeding flow. The shrinkage-induced feeding flow leads to an inverse (positive) segregation in the bottom part, and a severe negative segregation in the part below cross-sectional change. Thermo-solutal buoyancy leads to a so-called steepling convection in the main part of the sample (away from the bottom and cross-sectional change), and this kind of flow leads to a positive macrosegregation near the sample surface. The calculations have successfully explained the experimental result of macrosegregation.
AB - A unidirectional solidification experiment of hypoeutectic Al-7.0 wt% Si alloy against gravity direction in a cylindrical mold with cross-sectional change was made, and the macrosegregation in different parts of the as-solidified sample was investigated (Ghods et al. in J Cryst Growth 441:107–116, 2016; J Cryst Growth 449:134–147, 2016). The current study is to use a two-phase columnar solidification model to analyze the segregation mechanisms as used in this experiment. Following flow phenomena and their contributions to the formation of macrosegregation are simulated and compared: (1) solidification shrinkage-induced feeding flow; (2) thermo-solutal convection; and (3) combined thermo-solutal convection and shrinkage-induced feeding flow. The shrinkage-induced feeding flow leads to an inverse (positive) segregation in the bottom part, and a severe negative segregation in the part below cross-sectional change. Thermo-solutal buoyancy leads to a so-called steepling convection in the main part of the sample (away from the bottom and cross-sectional change), and this kind of flow leads to a positive macrosegregation near the sample surface. The calculations have successfully explained the experimental result of macrosegregation.
KW - Directional solidification
KW - Fluid flow
KW - Macrosegregation
KW - Shrinkage
UR - http://www.scopus.com/inward/record.url?scp=85054907962&partnerID=8YFLogxK
U2 - 10.1007/s12666-018-1422-9
DO - 10.1007/s12666-018-1422-9
M3 - Article
AN - SCOPUS:85054907962
VL - 71.2018
SP - 2639
EP - 2643
JO - Transactions of the Indian Institute of Metals
JF - Transactions of the Indian Institute of Metals
SN - 0972-2815
IS - 11
ER -