Effect of casting procedures in the structure and flow behaviour of semisolid A356 alloy

• Autorzy: Proni C. T. W. , Robert M. H. , Zoqui E. J.
• Języki publikacji: EN

Abstrakty

EN

Purpose: Evaluation of different casting methods to produce raw material for thixoforming, aiming costs reduction in the production of thixoformable alloys. Reduction of costs may stimulate the commercial use of the semisolid processing technology (SSM). Design/methodology/approach: It is analysed the effect of different casting routes in the microstructure features in semisolid A356 alloy, and in its rheological behaviour. Different casting procedures were investigated: a) pouring in water cooled Cu mould; b) same as „a)” adding electromagnetic stirring; c) same as „a)” adding mechanical vibration; d) same as „b)” with addition of grain refiner; e) same as „c)” with addition of grain refiner. Cast materials were reheated to the semisolid sate and the effect of different holding times upon the globularization of the primary phase was analysed for each cast structure. The semisolid material in each condition was evaluated concerning rheological behaviour. Mechanical properties of thixoformed products were evaluated using flexion tests. Findings: Despite the several methods currently in use to produce raw material for thixoforming, this work shows that the best combination of quality of thixoformable material/ production cost /process operationality can be achieved using casting in permanent mould, under water cooling and mechanical vibration. Resulting cast material under this condition presents grain size smaller than 100 μm, ideal for SSM. Lower the grain size, lower the primary globule size and higher the roundness of the primary phase particle and lower the apparent viscosity of the semisolid. In the best condition achieved, apparent viscosity measured was circa 105 Pa.s (similar to the working range for glass), leading to a probable homogeneous die filling during thixoforming in high pressure die casting machines (HPDC). Research limitations/implications: Regardless the best microstructure for SSM resulting from casting under mechanical vibration, it is still necessary to reach the optimum casting condition in terms of vibration in order to improve, even more, refinement of the microstructure. Practical implications: The suggested process is a simple technique to reduce costs in the production of raw material for thixoforming. The technology is easily implementable in industries. Originality/value: The development of a simple, original, low cost method to produce raw material for SSM technology.

Słowa kluczowe

EN

thixoforming; semi-solid materials; A356 alloy; microstructure; rheological behavior; casting; flexion test

PL

odlewanie tiksotropowe; materiały półstałe; stop A356; mikrostruktura; zachowania reologiczne; odlewanie; próba przeginania

• Wydawca: International OCSCO World Press
• Czasopismo: Archives of Materials Science and Engineering
• Rocznik: 2015
• Tom: Vol. 73, nr 2
• Strony: 82--93
• Opis fizyczny: Bibliogr. 15 poz.

Twórcy

autor

Proni C. T. W.

• Materials and Manufacturing Department, School of Mechanical Engineering, University of Campinas, R. Mendeleiev, S/N, 13083-860, Campinas, SP, Brazil

autor

Robert M. H.

• Materials and Manufacturing Department, School of Mechanical Engineering, University of Campinas, R. Mendeleiev, S/N, 13083-860, Campinas, SP, Brazil

autor

Zoqui E. J.

• Materials and Manufacturing Department, School of Mechanical Engineering, University of Campinas, R. Mendeleiev, S/N, 13083-860, Campinas, SP, Brazil

Bibliografia

• [1] M.C. Flemings, Behavior of Metals in the Semisolid State, Metallurgical Transactions A 22 (1991) 957-981.
• [2] M.C. Flemings, W.L. Johnson, High Viscosity Liquid and Semi-Solid Metal Casting, World Foundry Conference, Kyong Ju, Korea, 2002, 20-24.
• [3] D.H. Kirkwood, M. Suéry, P. Kapranos, H.V. Atkinson, K.P. Young, Semi-solid Processing of Alloys, Springer Series in Material Science, 124, Springer- Verlag, Berlin Heidelberg, 2010, 172.
• [4] O. Lashkary, R. Ghomashchi, Rheological Behavior of Semi-solid Al-Si alloys: Effect of Morphology, Materials Science and Engineering A/454-455 (2007) 30-36.
• [5] M.S. Salleh, M.Z. Omar, J. Syarif, M.N. Mohammed, An Overview of Semisolid Processing of Aluminium Alloys, ISRN Materials Science, 2013, 1-9.
• [6] C.T.W. Proni, Efeito da taxa de aquecimento no desmantelamento e na globularização da microestrutura para propiciar a tixoconformação, PhD Thesis, University of Campinas, Brazil, (2014), 210 (in Portuguese).
• [7] T. Haga, R. Nakamura, S. Kumai, H. Watari, Clad Strip Casting by a Twin Roll Caster, Archives of Materials Science and Engineering 37/2 (2009) 117-124.
• [8] A. Ohno, Solidification, The Separation Theory and its Practical Applications, Springer-Verlag Berlin Heidelberg New York London Paris Tokio, 1987.
• [9] H.V. Atkinson, Modelling the Semisolid Processing of Metallic Alloys, Progress in Materials Science 50 (2005) 341-412.
• [10] M. Marzouk, M. Jain, S. Shankar, Effect of Sr-Modification on the Bendability of Cast Aluminum A356 Using Digital Image Correlation Method, Materials Science & Engineering A/598 (2014) 277-287.
• [11] E.J. Zoqui, M. Paes, E. Es-Sadiqi, Macro and Microstructure Analysis of SSM A356 Produced by Electromagnetic Stirring, Journal of Materials Processing Technology 120/1-3 (2012) 365-373.
• [12] T. Motegi, F. Tanabe, M.H. Robert, E.J. Zoqui, Producing Thixotropic Semisolid A356 alloy: Microstructure Formation x Forming Behaviour, Journal of Achievements in Materials and Manufacturing Engineering 20/1-2 (2009) 19-26.
• [13] G.F. Vander Voort, ASM Handbook, Metallography and Microstructures v. 9, ASM Int., 2004.
• [14] V. Laxmanan, M.C. Flemings, Deformation of Semisolid Sn-15 Pct Pb, Metallurgical Transactions A 11 (1980) 1927-1937.
• [15] M. Cholewa, M. Dziuba-Kaluza, Analysis of structural properties of aluminum skeleton castings regarding the crystallization kinetics, Archives of Materials Science and Engineering 38/2 (2009) 93-102.