Naslov
Investigation of AlMg9 alloy microscopic features related to cooling rate

Autori
Zovko Brodarac, Zdenka ; Mrvar, Primož ; Unkić, Faruk

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Croatian Microscopy Symposium, Book of Abstract / Gajović, A. ; Tomašić, N. - Zagreb : Hrvatsko mikroskopijsko društvo, 2012, 37-38

ISBN
978-953-57138-1-4

Skup
Croatian Microscopy Symposium

Mjesto i datum
Pula, Hrvatska, 16.11.2012. - 17.11.2012

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
Al-Mg alloy; cooling rate; microstructure; grain size

Sažetak
Recently, foundry Al-Mg alloys play an important role in overall foundry industry of light metals due to their high strength and ability for precipitation hardening at higher magnesium contents. Magnesium has imposed itself due to his basic advantages over the all structural materials: low density, which has directly influenced lowerness of the casting weight, and indirectly ecologically acceptable safety parts because of the reduced emission of CO2, as well as suitability for recycling. Typical application of Al-Mg alloys include: tool plates, complex thin-walled shapes such as rotor limbs, cooling plates used by mechanical processing, instruments housing, ship parts, gun frames and optical systems. The best strength and toughness ratio has binary Al-Mg alloy with 10 wt. % Mg, however this is an alloy with the most difficult castability due to its tendency to porosity, slag forming and high viscosity [1]. Maximum solubility of magnesium in aluminum is 15, 3 wt.% at eutectic temperature, subsequently the cast alloys have been choose from the α – phase region. Increase of the binary alloy strength has been achieved with an increase of solute magnesium in solid solution of aluminum. Although some of the phases, such as Al8Mg5, (Al3Mg2, β-phase) has been precipitated below the eutectic temperature, they do not have any influence on the strengthening due to precipitating as coarse particles on grain boundaries. This is the reason for the ternary system development. One of the most applicable systems is aluminum – silicon – magnesium which is strengthening through the precipitation of the metastable compound Mg2Si. Compound Mg2Si is in equilibrium with aluminum and quasi-binary line Al-Mg2Si at the ratio Mg:Si = 1, 73 [2, 3]. Different cooling rates have been achieved by casting in special moulds. Cooling was performed by rates of 0, 17 ; 3 ; 7, 55, and 150 K/s. Also, quenching through entire solidification interval was performed in order to determine development of microstructural constituents. Microstructure features analysis has been performed on the optical, as well as on the scanning electron microscope (SEM) which has resulted in visual recognition of individual phases on their morphology basis [4]. Chemical composition determination of each phase was carried out by the energy dispersive specter (EDS) by which the identification of Alx(MnFe)ySiz, Mg2Si and Al8Mg5 phases were performed. Phase analysis, surface area, elongation and number of grains per surface area (NA) of the corresponding microstructure were established related to the cooling rates. Microstructural investigations of the multicomponent technical AlMg9 alloy resulted in the qualitative and quantitative description of the solidification sequence and mechanism at corresponding cooling rates in real systems.

Izvorni jezik
Engleski

Znanstvena područja
Metalurgija

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