engleski

Influence of the cooling rate on the microstructure development of the EN AW-AlMg4.5Mn0.7 alloy

In this work, the course of the solidification and development of the microstructure of a sample of the EN AW-AlMg4.5Mn0.7 alloy, taken out from the edge of a slab cast with a semi- continuous, vertical, direct water-cooling process (DC) was studied. In order to determine the influence of the cooling rate on the type, the morphology and the solidification course of some phases in EN AW-AlMg4.5Mn0.7, a simultaneous thermal analysis using differential scanning calorimetry was conducted. Its results were compared with the thermodynamically calculated equilibrium phases obtained on the basis of the Thermo-Calc software. The results were also compared with the results of a simple thermal analysis, which was conducted by casting the sample in a specially designed measuring cell using the Croning process and in a cone- shaped measuring cell. The temperature intervals of the reference temperature-phase transitions (the liquidus temperature TL, the temperature evaluation of the first eutectic TE1 and the second eutectic TE2 and the solidus temperature TS) and the times of the solidification ts of the EN AW-AlMg4.5Mn0.7 alloy were determined. The mathematical models describing the changes in these parameters depending on the cooling rate were made. Using a quantitative analysis carried out with an energy dispersive spectrometer, the following microstructural constituents were determined: the intermetallic phase Al6(Fe, Mn), which, due to an unequilibrium evaluation, corresponds to the first eutectic (Al + Al6 (Fe, Mn) and the Mg2Si intermetallic phase, as the second eutectic phase (Al + Mg2Si). In addition, the presence of the pores was determined. The total surface area of some intermetallic phases and pores and their distribution in dependence on the cooling rate were examined by a scanning electron microscope.

EN AW-AlMg4.5Mn0.7 alloy ; cooling rate ; microstructure

nije evidentirano