Naslov
Strjevanje zlitine AlMg9
(Solidification of the AlMg9 Alloy)

Autori
Zovko Brodarac, Zdenka

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Naravoslovnotehniška fakulteta

Mjesto
Ljubljana

Datum
10.06

Godina
2009

Stranica
152

Mentor
Mrvar, Primož ; Medved, Jožef ; Unkić, Faruk

Ključne riječi
AlMg9 alloy (EN AC 51200) ; solidification ; quenching experiments ; thermal analysis ; microstructural characteristics

Sažetak
Recently, foundry Al-Mg alloys play an important role in overall foundry industry of light metals due to their high strength and ability of precipitation hardening for higher magnesium contents. Due to the silicon addition for the precipitation strengthening purpose new Al-Mg-Si systems has been developed. The solidification sequence of the multicomponent technical AlMg9 alloy has been investigated in this thesis through several methods of thermal and microstructure characteristics analysis. Influence of the cooling rate on the significant temperatures of phase changes during solidification and the grain size of multicomponent technical AlMg9 alloy have been determined. Cooling has been performed by the established rates of 0, 17 ; 1, 7 ; 3 ; 7, 12 ; 55 and 150 K/s. Significant temperatures of phase changes have been accompanied and identified through simultaneous and simple thermal analysis, as well as through the thermodynamical modeling by ThermoCalc which enables development of corresponding physical models. Mathematical models of significant temperature and cooling rate dependence have been made. Solidification simulation has been performed through the finite elements method by the ProCast software, which has been compared with the real cooling curves. Besides this, the grain size (G) and the number of grains per surface area (NA) for each cooling rate have been determined as well as their correlation. Microstructure characteristics analysis has been performed on optical, and on scanning electron microscope (SEM) which has resulted in visual recognition of individual phases on their morphology basis. Chemical composition determination of each phase was carried out by the energy dispersive spectroscopy (EDS), by which the identification of Alx(Mn, Fe)ySiz, (α Al + Mg2Si) and (α Al + Al8Mg5) has been determined in the microstructure. Phase analysis, surface area, elongation and number of grains per surface area (NA) of the corresponding microstructure were established related to the cooling rates. Solidification sequence as well as the microstructure development has been followed through the “ disturbed” solidification process by quenching. This process allowed examination and correlation of significant temperatures of phase changes and obtained microstructure characteristics of each phase. Quenching temperature and time were correlated to the microstructure development in order to establish kinetic of the solidification.

Izvorni jezik
Engleski

Znanstvena područja
Metalurgija

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