Simplified Rheocasting of Al-Si Alloys Sheared by Mechanical Stirring

Abstract:

A rheocasting prototype for the semi-solid processing of Al-Si alloys was designed and assembled at laboratory scale, this is the first attempt for the development of S2P equipment in Mexico. This work describes the simplified method of mechanical stirring and the calculation of the theoretical parameters for the operation of the experimental device in order to provide shear rate into the slurry by a stainless steel impeller inside a crucible made of hot work steel. Moreover, a vertical pressure die-rheocasting system it is applied with the semi-solid alloy flowing counter the position of the injector during the displacement of the crucible in order to fill the mold. New design is applied in this rheocasting equipment.The semi-solid state with thixotropic behavior is produced in the stirred AlSi7Mg alloy; this condition allows the non-dendritic morphology because the intensively stirring at the beginning of the solidification produces the trimming of dendrites, growing so the primary solid (α) in globular shape surrounded by eutectic microstructure. Preliminary microstructural characterization was performed.

• Periodical: Key Engineering Materials (Volumes 651-653)
• Pages: 1545-1550
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.651-653.1545
• Online since: July 2015
• Authors: Alfredo Hernández*, J. Federico Chávez, Raquel E. Hernández
• Keywords: Non-Dendritic Microstructure, Rheocasting, Semi-Solid Processing, Thixotropic Behavior

References

[1] Kotadia, H.R., Hari, B.N., Zhang, H., Arumuganathar, S., Fan, Z., Solidification Behavior of Intensively Sheared Hypoeutectic Al-Si Alloy Liquid, The Minerals, Metals & Materials Society and ASM International (2010).

DOI: 10.1007/s11661-010-0516-8

[2] Plato Kapranos, Semi-Solid Metal Processing – A Process Looking for a Market, Solid State Phenomena (2008); Vols. 141-143, pp.1-8.

DOI: 10.4028/www.scientific.net/ssp.141-143.1

[3] Rosso, M., Thixocasting and rheocasting technologies, improvements going on, Journal on Achievements in Materials and Manufacturing Engineering, Vol. 54, 1, (2012), pp.113-114.

[4] Flemings, M. C., Behavior of metal alloys in the semisolid state, Metallurgical Transactions (1991); vol. 22A, pp.957-981.

DOI: 10.1007/bf02661090

[5] N. Barman, P. Dutta, Rheological Behavior of Semi-solid Slurry of A356 Alloy at High Shear and Cooling Rates, Solid State Phenomena (2008); Vols. 141-143, pp.409-414.

DOI: 10.4028/www.scientific.net/ssp.141-143.409

[6] Figueredo, K., Flemings, M.C., Viscosity of semi-solid A357 alloy in the transient high shear rate regime, Metallurgical Science and Technology (2000); Vol. 18 (2), pp.32-36.

[7] Atkinson, H.V., Modelling of Semi-solid Processing, Shaker Verlag, Aachen, (2008).

[8] Quaak, C.J., Rheology of partially solidified aluminum alloys and composites, PhD Thesis, Technishe Universiteit of Delft, Nederlands, (1996).

[9] Nishizawa, T., Thermodynamics of Microstructures, ASM International, (2008).

[10] Hirt, G., Kopp, R., Thixoforming, Semi-solid Metal Processing, Wiley-VCH Verlag, (2009), 32-36.

[11] Azpilgain, Z., Desarrollo y caracterización de aleaciones de aluminio e implementación de un sistema de forja para el conformado en estado semi-sólido, PhD Thesis, Mondragon Unibertsitatea, Spain, (2006).