Predicting the Effect of Pouring Temperature on the Crystallite Density, Remelting, and Crystal Growth Kinetics in the Solidification of Aluminum Alloys

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2014-08, Vol.45 (4), p.1407-1417
• Main Authors: Ferguson, J. B., Tabandeh-Khorshid, Meysam, Mantas, John C., Rohatgi, Pradeep K., Cho, Kyu, Kim, Chang-Soo
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum alloys; Aluminum base alloys; Applied sciences; Bottom casting; Characterization and Evaluation of Materials; Chemistry and Materials Science; Crystallites; Crystals; Density; Exact sciences and technology; Grain size; Intermetallic compounds; Kinetics; Materials Science; Mathematical models; Metallic Materials; Metals. Metallurgy; Nanotechnology; Pouring; Production of metals; Solidification; Structural Materials; Surfaces and Interfaces; Temperature effects; Thin Films
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-014-0044-9

In the present work, we developed an analytical model to describe the effect of pouring temperature on the crystallite density, remelting, growth kinetics, and the resultant final grain size for aluminum (Al)-based alloys synthesized using gravity casting. The model predicts that there are three regimes of pouring temperature/grain size-related behavior: (i) at low superheats, grain size is small and relatively constant; (ii) at intermediate levels of superheat, there appears to be a transitional behavior where grain size increases in a rapid, non-linear fashion; and (iii) at high superheats, grain size increases linearly with increasing temperature. This general pattern is expected to be shifted upward as distance from the bottom of the casting increases, which is likely a result of the slower cooling rates and/or longer solidification times with increasing distance from the bottom of the casting. To validate the model, a set of experiments has been conducted using Al-Cu and Al-Si alloys ( i.e. , Al-3.0 wt pct Cu, Al-4.5 wt pct Cu, and Al-A356.2 alloys), and the experimental measurements showed consistent results with theoretical predictions.