EFFECT OF ADDITIONAL ALLOYING AND HEAT TREATMENT ON THE PHASE COMPOSITION AND MORPHOLOGY IN Al-Mg-Si TYPE CASTING ALLOY
DOI:
https://doi.org/10.7494/mafe.2017.43.3.219Keywords:
casting alloys, high pressure die casting, aluminium alloys, structure, precipitation, heat treatmentAbstract
The structure of permanent mold and high pressure die castings of the AlMg5Si2Mn alloy after alloying with Li and Sc has been investigated by scanning and transmission electron microscopy, hardness and microhardness measurements, energy dispersive X-ray analysis. Three conditions, as cast, solution treated and aged, were investigated. It was shown that in as-cast state, the structure of an alloy having the nominal composition AlMg5Si2Mn consists of four phases: first – the Al based solid solution, second – the (Al)+(Mg2Si) eutectic, third – the primary Mg2Si crystals and fourth – the a-Al(Mn, Fe)Si phase. Similar phases were observed in the alloys containing Sc or Li. After two days of storing in an as-cast condition, the solid solution in all tested alloys decomposes
and forms zebra-crossing shaped precipitates. TEM examinations revealed that these precipitates nucleate heterogeneously on dislocations. The solution treatment at 575.0°C results in spheroidization of the Mg2Si lamellas, dissolution of the precipitates and formation of a-Al(Mn, Fe)Si dispersoids, nucleating on the surfaces of Mg2Si lamellas. In the Sc containing alloys, the formation of Al3Sc was detected after 120 min soaking. Further heating resulted in the growth of these precipitates. Aging of the Al-Mg-Si alloys leads to an increase of hardness in all studied alloys. This effect is mainly related to precipitation strengthening, via solid solution decomposition and formation of b’’-phase. In Li-alloyed specimens, plates of b Mg2Si phase were observed together with small cubic-shaped d’ Al3Li precipitates.
The structure of permanent mould and high pressure die castings of the AlMg5Si2Mn alloy after alloying with Li and Sc has been investigated by scanning and transmission electron microscopy, hardness and microhardness measurements, energy dispersive X-ray analysis. Three conditions, as cast, solution treated and aged, were investigated. It was shown that in as-cast state, the structure of an alloy having the nominal composition AlMg5Si2Mn consists of four phases: first - the Al based solid solution, second - the (Al)+(Mg2Si) eutectic, third - the primary Mg2Si crystals and fourth – the phase. Similar phases were observed in the alloys containing Sc or Li. After two days of storing in an as-cast condition, the solid solution in all tested alloys decomposes and forms zebra-crossing shaped precipitates. TEM examinations revealed that these precipitates nucleate heterogeneously on dislocations. The solution treatment at 575.0°C results in spheroidization of the eutectic, dissolution of the precipitates and formation of dispersoids, nucleating on the surfaces of Mg2Si lamellas. In the Sc containing alloys, the formation of Al3Sc was detected after 120 min soaking. Further heating resulted in the growth of these precipitates. Aging of the Al-Mg-Si alloys leads to an increase of hardness in all studied alloys. This effect is mainly related to precipitation strengthening, via solid solution decomposition and formation of b²-phase. In Li-alloyed specimens, plates of b Mg2Si phase were observed together with small cubic-shaped d¢ Al3Li precipitates.
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References
Ritter F.: Korrosionstabellen metallischer Werkstoffe geordnet nach angreifenden Stollen. Springer-Verlag Wien GmbH, 1937
D‘Ans J., Lax E.: Taschenbuch für Chemiker und Physiker. Springer-Verlag Berlin Heidelberg GmbH, 1949
Pirs J., Zalar A.: Investigations of the distribution of elements in phases present in G-AlMg5Si cast alloy with EDX/WDX spectrometers and AES. Microchimica Acta, 101, 1–6 (1990), 295–304
Pirs J.: Distribution of elements in phases present in G-AlMg5Si cast alloy. Aluminium, 69, 5 (1993), 462–465
Aluminium Rheinfelden GmbH brochure, DG-Handbuch 07 (Primary Alloys for Die Casting)
Hielscher U., Sternau H., Koch H., Franke A.J.: Magsimal-59, an AlMgSiMn-type squeeze-casting alloy designed for temper F. Aluminium Rheinfelden GmbH, Rheinfelden, Germany
Jorstad J.L.: Excellent die casting alloy system made better rheocasting. Die Casting Engineer, September 2008, 18–20
Hydro Aluminium Metal Products. TechInfo-Foundry Alloys. New Alloys for High Pressure Die Casting AlMgSiMn
Progress in Aluminium, SAG Aluminium Lend GmbH & Co KG brochure, 2005
Casting alloys MAXXALLOY® - ULTRA© GBD-AlMg5Si2MnCr - REAluminium Lend GmbH & Co KG
Otarwanna S., Gourlay C.M., Laukli H.I., Dahle A.K.: Microstructure Formation in AlSi4MgMn and AlMg5Si2Mn High-Pressure Die Castings. Metallurgical and Materials Transactions A, 40 (2009), 1645–1659
Di Sabatino M., Arnberg L., Brusethaug S., Apelian D.: Fluidity evaluation methods for Al-Mg-Si alloys. International Journal of Cast Metals Research, 19, 2 (2006), 94–97
Ji S., Watson D., Fan Z., White M.: Development of a Super Ductile Diecast Al-Mg-Si Alloy. Materials Science & Engineering A, 556 (2012), 824–833
Hu Z., Wan L., Lu S., Zhu P., Wu S.: Research on the microstructure, fatigue and corrosion behavior of permanent mold and die cast aluminum alloy. Materials and Design, 55 (2014), 353–360
Petkov T., Künster D., Pabel T., Faerber K., Kneiβl C., Schumacher P.: Optimierung der Wärmebenhandlung einer AlMgSi-Gusslegierung. Druckguss, 6 (2012), 268–274
Petkov T., Kunstner D., Pabel T., Faerber K., Kneissl C., Schumacher P.: Erweiterung des Eigenschaftspotentials der Legierung AlMg5Si2Mn durch eine gezielte Wärmebehandlung Berg- und Hüttenmännische Monatshefte, X (2013), 1–9, Jvn. Jg. (2013), Heft X© Springer-Verlag Wien, 1–9
Ji L., Watson D., Fan Z., White M.: Development of a super ductile die cast Al-Mg-Si alloy. Material Science and Engineering A, 556 (2012), 824–833
Eigenfeld K., Franke A., Klan S., Koch H., Lenzcowski B., Pflege B.: New developments in heat resistant aluminum casting materials. Casting Plant and Technology International, 4 (2004), 4–9
Fridlyander J.N., Bratukhin A.G., Davydov V.G.: Soviet Al-Li Alloys of Aerospace Application, Aluminum-lithium. In: Proceedings of the Sixth International Aluminum-Lithium Conference in Garmisch-Partenkirchen,
Peters M. and Winkler P.-J. eds., Germany, Vol. 1, 1991, 35–42.
Sauermann R., Friedrich B., Grimmig T., Buenck M., Buhrig-Polaczek A.: Development of Aluminium-Lithium alloys processed by the Rheo Container Process. Solid State Phenomena, 116–117 (2006), 513–517
Barabash O.M., Sulgenko O.V., Legkaya T.N., Korzhova N.P.: Experimental Analysis and Thermodynamic Calculation of the Structural Regularities in the Fusion Diagram of the System of Alloys Al-Mg-Si. Journal
of Phase Equilibria, 22, 1 (2001), 5–11
Barabash O.M., Sulzhenko O.V., Legkaya T.N., Korzhova N.P.: Thermodynamic calculation and experimental analysis of the phase diagram of Al-Mg-Si system. Functional Materials, 8, 1 (2001), 154–158
Boyko V., Link T., Korzhova N., Mykhalenkov K.: Microstructure characterization of AlMg5Si2Mn casting alloy. In: Materials Science and Technology (MS&T) 2013, October 27–31, Montreal, Quebec, Canada,
, 1331–1338
Chen R., Huang Z., Chen C.Q., Shen J.Y., Zhang Y.G.: Thermodynamic calculated and TEM observed microstructure of Al-Li-Mg-Si alloys. Materials Science and Engineering A, 280 (2000), 146–150
Murken J., Höhner R., Skrotzki B.: Strain path dependence of the precipitate size evolution of an Al-Mg-Li alloy under combined thermal and mechanical loading. Materials Science and Engineering A, 363 (2003), 159–170