Analysis of crystallization kinetics of cast aluminum–silicon alloy

Abstract

Light alloys like aluminum and its alloys have excellent physical and mechanical properties for a number of applications. The use of aluminum alloys can significantly decrease the mass of automobiles without decreasing structural strength. Therefore, the reason of this work was to determine the optimal cooling rate values, to achieve good mechanical properties for protection of this aluminum cast alloy from losing their work stability, and to make it more resistant to action in hard working conditions. The carried out investigations have allow to found that changes in the cooling rate do not cause changes in the phase composition, revealing the Al 2 Cu and Al 5 FeSi phase especially, but only changes the morphology of a ? b eutectic as well as the particle size and secondary dendrite arm spacing. As a result, the number of fine crystals in per unit volume increases, leading to a fine grain structure, which influences the recalescence temperature. The purpose of this research work is to investigate the thermoderivative interdependencies occurred in analyzed aluminum cast alloys using Universal Metallurgical Simulator and Analyzer. For the investigation, the cast AlSi9Cu aluminum alloy was used. As a result of this research, the cooling rate influence on the structure and mechanical properties changes was investigated. The cooling rate was set in a variable range of 0.16-1.25°C s -1 , where the cooling rate of 0.16°C s -1 corresponds to freely cooling, without any forced air flow.

Analysis of Crystallisation Process of Cast Magnesium Alloys Based on Thermal Derivative Analysis / Analiza Procesu Krystalizacji Odlewniczych Stopów Magnezu W Oparciu O Analizę Termicznoderywacyjną

“…Base on the results of combined LM, SEM and EDS analyses, which were shown in Figs 3-8, it was verified that in the structure of analysed magnesium alloys, the bright plate-shaped particle containg Al-Mn, dark polygonalshaped particle was a Mg-Si and the irregular shaped particle extends along primary magnesium dendrites; moreover it has been noticed that grain boundaries at the final solidification regions was a Mg 17 Al 12 . Distribution of intermetallic compounds in the microstructure, such as Mg-Si and AlMn located on the edge of γ phase and at grain boundaries or in the interdendritic regions, indicates that these phases precipitated before eutectic reaction and simultaneous precipitation at higher temperature.…”

“…It appears that the peaks correspond to the crystallisation of primary magnesium dendrites, the formation of secondary phases at the interdendritic regions, the eutectic solidification reaction, and the final solidus reaction, respectively. a) b) 12 phase is forming from the eutectic reaction also arise Mg 17 Al 12 phase according to the discontinuous mechanism. In both discontinuous γ phase and α+γ crystallise as multicomponent eutectic, where its content is a 32.3% of Al.…”

“…Hence, the latent heat directly given to the test sample affected the fraction liquid development. Similar estimates were completed for the fraction solid, except that fraction solid was proportionate to the latent heat released during the crystallisation [8,12,13].…”

“…Figure 9 shows the X-ray diffraction analysis of MC Mgal6zn1 and Mc Mgal9zn1 magnesium alloys. The XRD pattern presents the high intensity of magnesium reflections and low intensity of Mg 17 Al 12 . Moreover, the X-ray analysis has not indicated an occurrence of an intermetallic compound containing Mg-Si and compound containing Al-Mn.…”

Mechanical Properties of High-Mn Austenitic Steel Tested under Static and Dynamic Conditions

“…Ductile cracking is a property describing the ability of the material containing cracks to withstand cracking [5][6][7]. It is pointed out by analysing the literature data that the plastic deformation energy of engineering materials can be used to prevent their damage before their decohesion process takes place, which became a basis for studies identifying the ability of steels containing at least 25% Mn with an austenitic structure with the addition of Al and Si, to prevent cracking by, notably, activation of mechanical twinning during cold plastic deformation [8][9][10][11]. Steel can be additionally strengthened by adding microadditions of Ti, Nb and B [12,13] to such steels, by employing thermomechanical treatment in a manufacturing process through refinement of an austenite structure.…”