UDK 669.715:620.187:544.015.4 Original scientific article/Izvirni znanstveni članek ISSN 1580-2949 MTAEC9, 46(6)563(2012) INFLUENCE OF THE COOLING RATE ON THE MICROSTRUCTURE DEVELOPMENT OF THE EN AW-AlMg4.5Mn0.7 ALLOY VPLIV OHLAJEVALNE HITROSTI NA RAZVOJ MIKROSTRUKTURE V ZLITINI EN AW-AlMg4,5Mn0,7 Natalija Dolic1, Jožef Medved2, Primož Mrvar2, Faruk Unkic1 JUniversity of Zagreb, Faculty of Metallurgy, Aleja narodnih heroja 3, 44103 Sisak, Croatia 2University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Materials and Metallurgy, Aškerčeva c. 12, 1000 Ljubljana, Slovenia ndolic@simet.hr Prejem rokopisa — received: 2012-03-01; sprejem za objavo - accepted for publication: 2012-04-05 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 Ats 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 (aAl + Ale(Fe, Mn) and the Mg2Si intermetallic phase, as the second eutectic phase (<«ai + 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. Keywords: EN AW-AlMg4.5Mn0.7 alloy, cooling rate, microstructure V delu obravnavamo potek strjevanja in razvoj mikrostrukture zlitine EN AW-AlMg4,5Mn0,7. Vzorec je bil odvzet na robu slaba, ulitega po polkontinuirnem postopku z direktnim vodnim hlajenjem v navpični smeri ("DC"). Za opredelitev vpliva ohlajevalne hitrosti na potek strjevanja v zlitini EN AW-AlMg4,5Mn0,7 in s tem na razvoj faz je bila uporabljena simultana termična analiza z diferenčno vrstično kalorimetrijo. Dobljene rezultate smo primerjali s termodinamsko ravnotežnimi izračuni posameznih faz. Izračun je bil narejen s programom "Thermo-Calc". Primerjava je bila narejena tudi z rezultati, dobljenimi z enostavno termično analizo. V tem primeru smo vzorec ulili v merilno celico, narejeno po postopku Cronning, in v trajno kokilo stožčaste oblike. Tako smo določili karakteristične temperature faznih transformacij (temperaturo liquidusa TL, temperaturo prvega TE1 in drugega evtektika TE2 ter temperaturo solidusa TS) ter čase strjevanja zlitine Ats. Za opis teh, od hitrosti odvisnih parametrov, smo izdelali tudi matematični model. Kvantitativna analiza posameznih faz oziroma identifikacija le-teh je bila narejena z energijsko-disperzijsko spektroskopijo rentgenskih žarkov. Opredeljene so bile naslednje mikrostrukturne sestavine: intermetalna faza Al6(Fe, Mn), ki je v zvezi z neravnotežnim strjevanjem prvega evtektika («ai + Ale(Fe, Mn)), intermetalno fazo Mg2Si, ki je del evtektskega heterogenega zloga (aAl + Mg2Si). Prav tako smo naredili analizo poroznosti. Za opredelitev deleža poroznosti, kot tudi posameznih intermetalnih faz in njihovo porazdelitev v odvisnosti od ohlajevalne hitrosti, je bil uporabljen vrstični elektronski mikroskop. Ključne besede: zlitina EN AW-AlMg4,5Mn0,7, ohlajevalna hitrost, mikrostruktura 1 INTRODUCTION Aluminum and its alloys are used in a variety of applications in industry and construction. Typical applications of aluminum alloys are found in the automotive industry, in the maritime, air and railway transportations. Recently, aluminum has been competing with steel in the automotive industry for the production of engine parts, suspensions and car-space frames. In most of these applications rolled products are used with a thickness of 0.1-25 mm.1 Intensive industrial competition requires a continuous quality improvement. The main motivation for this activity originates in the growing demands of the industry for a development of high-strength alloys in order to reduce the weight of various products.1 Aluminum-magnesium alloys constitute a group of non-heat treatable alloys with a medium strength, high ductility, an excellent corrosion resistance and weld-ability (the 5XXX series). Wrought Al-Mg alloys are used as structural materials for marine, automotive, aircraft and cryogenic applications, while their cast forms are mainly used, due to the corrosion resistance, in dairy, food-handling and chemical-processing applications.2-4 The EN AW-AlMg4.5Mn0.7 alloy is one of the most popular commercial alloys that is mostly used for ship structures due to its superior resistance against corro- sion.5 The non-heat treatable aluminum alloys are utilized in all of the major industrial markets for aluminum flat-rolled products. At the end of the 20th century, transportation, packaging and building/construction sectors represented the largest users of the non-heat-treatable sheets. High-performance, non-heat-treatable alloys were developed for the new and existing applications ranging from foil to high-strength structural products. The development of the new or improved alloys was based on the need for a structural performance or appearance in the end products and the productivity during the customer's manufacturing process.1 The polythermal section of the ternary Al-Mg-Mn phase diagram shown in Figure 1 gives us the first approximation of the phase-transformation history for the alloys like EN AW-5083, EN AW-5182, and EN AW-5456 containing the mass fraction of Mg 4.0-7.0 % and 0.3-0.6 % Mn. The solidification starts at 635-640 °C with the formation of the Oai grains. After that, providing that the concentration of Mn is sufficient, the (oai + Al6Mn) eutectics are formed in the temperature range from 627 °C to 617 °C. These reactions seldom occur during the cooling following the solidification because, due to a relatively low diffusion coefficient, manganese usually remains in the supersaturated solid solution.6 The presence of silicon, as an impurity or an alloying element, in the Al-Mg-Mn alloys results in the formation of Mg2Si in addition to other phases. Most commercial alloys contain iron as an impurity. As a result, the (oai + /00 615 600 O o F: 500 f" 00 400 (1) Q. fc (1) 300 1- 205 \ 200 100 L 627_____- --TÏÂiT |L+(AI iy -f- L+(AI)+AI6 (AI) ',/', (ai)+ai6 k ■ 0.37j , i Yj ' JOA ■ ^ (Al)- hAI10+AI6 -^55^2.75 f\j(AI)+Al10+AI8 L_i__s. ■ i 264 1 2 2.73 3 w(Mn) / mass % AI-5% Mg\ (AI)+AI8 Al10: AI10(MgMn)3 Al8: AI8Mg5 Al6: AI6Mn Figure 1: Isopleths of the Al-Mg-Mn phase diagram at the mass fraction of Mg 5 % 6 Slika 1: Ravnotežni izopletni fazni diagram Al-Mg-Mn pri masnem deležu Mg 5 % 6 Al6(Fe, Mn)) eutectics are formed in the temperature range from 600 °C to 570 °C, and the solidification is completed at approximately 570 °C with the formation of the (aAl + AF(Fe, Mn) + AFFe) eutectics. Under equilibrium, the other phases that are frequently observed in the Al-Mg-Mn-Fe alloys, e.g., AlsMg5 (previously known as AFMg27-9) and Alw(Mg, Mn)3, are formed only due to the precipitation from the aluminum solid solution upon cooling in the solid state. Under the real, non-equilibrium conditions, these phases can be formed during the solidification being a result of the eutectic reaction.6 In the case of a simultaneous presence of iron and silicon in a 5XXX series alloy containing 5 % Mg (e.g., the EN AW-5182 alloy), the solidification will end at 576-578 °C with the formation of Mg2Si by a eutectic reaction.6 The solidification paths that we considered above, describe the phase equilibrium and can hardly be accomplished under the real casting conditions when the cooling rates are high and the diffusion processes, especially in the solid phase, cannot be completed to such an extent that the compositions of the phases change with the temperature in accordance with the equilibrium-phase diagram. Local deviations from equilibrium result in a microsegregation and, eventually, in the shift of local equilibrium to the concentrations, where new phases are formed. In addition, some high-temperature peritectic reactions remain uncompleted and the high-temperature phases - that have to disappear as a result of these reactions - are retained at a lower temperature and can be found in the solid state.6 For all aluminum-alloy components, the casting process plays an important role in controlling the properties of the final products. Semi-continuous Direct Chill (DC) casting is the most common method used for producing aluminum-alloy ingots for the subsequent thermomechanical processing (TMP), such as rolling and extrusion.1011 Casting defects such as microsegregation and porosity are usually present in the as-cast microstructure and can lead to a deterioration of mechanical properties. Many studies have shown a detrimental effect of porosity on the fatigue properties of the materials used in the as-cast or heat-treated state.1112 2 EXPERIMENTAL WORK Tests were carried out on a sample of an ingot cast by semi-continuous, vertical, direct water-cooling process (Direct Chill), having the dimensions of 520 mm x 1 680 mm x 4 809 mm and being produced from charge 3116 of the EN AW-AlMg4.5Mn0.7 alloy (the numerical symbol EN AW-5083).13 The structure of the tested alloy 3116 contains a significantly higher share of the technological waste, compared to the primary aluminum, in the ratio of 75 : 25. The main components of the technological waste are the alloys EN AW-1050, EN AW-5049 and EN AW-5754. Before casting, the melt was refined with a mixture of argon and chlorine in an ALPUR unit. The grain refinement was performed by adding the AlTi5B master alloy in the form of small bars (in the melting furnace) and wires (into the groove in front of ALPUR), in an average quantity of 1.74 kg/t of the melt.14 From the ingot cast in this way, an about 30-mm thick, transversally cut plate was taken out from its front part, after having been disposed of the technological waste of about 200 mm at the beginning of the casting. From the cut plate, from its edge, a part of the ingot was taken out and used to perform tests with a simple thermal analysis (STA) and differential scanning calorimetry (DSC). The thermodynamical calculation of the phase equilibrium of the EN AW-AlMg4.5Mn0.7 charge-3116 alloy was preliminary performed by the Thermo-Calc (TCW 5.0) software. This software allows a calculation of the phase stability of particular phases taking into account the equilibrium conditions of temperature, pressure and chemical composition. The simple thermal analysis was performed on sample 6P-1 (in the as-cast condition) taken out from the beginning of the cast ingot of charge 3116. Sample 6P-1 was molten in the graphite pot of an electric furnace. When the melt reached the temperature of approximately 730 °C, it was poured from the graphite pot into two measuring cells: into a cell made with the Croning process (equipped with a single thermocouple in the middle), Figure 2a, and a permanent cone-shaped measuring cell (Figure 2b). For the characterization of the solidification of sample 6P-1 at different cooling rates, the cone-shaped measuring cell of grey cast iron was used with three thermocouples installed in it. The described measuring cells are illustrated in Figures 2a and 2b. The samples for the metallographic and microstructural investigations were taken out from the corresponding place in the immediate neighborhood of the thermocouple. These samples are illustrated in Figures 3a and 3b. The samples for the metallographic and microstructural investigation were prepared with a standard Figure 2: Measuring cell made: a) with the Croning process and b) the cone-shaped grey iron-measuring cell Slika 2: Merilna celica, narejena: a) po postopku Croning in b) stožča-sta merilna celica iz sive litine Figure 3: Sampling methodology for the metallographic and microstructural analysis with the marked places of the performed analysis: a) photography of a cut sample poured into the measuring cell made with the Croning process with a marked place of sample taking and a description; b) photography of a cut sample poured into the permanent cone-shaped measuring cell with the marked places of sample taking and a description Slika 3: Prikaz mesta odvzema vzorcev v ulitku za metalografsko in mikrostrukturno analizo s pripadajočimi oznakami: a) slika razrezanega in označenega vzorca, ulitega v merilno celico Croning, b) slika razrezanega in označenega vzorca, ulitega v trajno stožčasto merilno celico iz sive litine procedure of grinding and polishing, and afterwards etching in 0.5 % HF. The samples for the microstructural investigation were examined on a scanning electron microscope (SEM) TESCAN VEGA TS5136LS with phase recognition performed on the basis of a chemical-composition analysis made with the energy dispersive spectrometer (EDS). The cooling curves were obtained with a data acquisition during the cooling and solidification processes using a measuring card DAQ Pad-MI0-16XE-50 and the corresponding software LabView 7.0. The cooling curves were afterwards plotted and analyzed with the Origin 7.0 software, determining the reference temperatures of the phase transformation in real samples. A simultaneous thermal analysis was performed with the differential scanning calorimetry (DSC) method on the NETZSCH equipment, type Jupiter 449C on sample 6P-1 using the heating and cooling techniques with the purpose of establishing the reference temperatures of phase transformations and solidification intervals, as well as the corresponding enthalpies and the specific heat extraction for each phase. 3 RESULTS AND DISCUSSION The chemical composition of the investigated charge was determined with an optical emission spectrometer and it is presented in Table 1. The sample for the Table 1: Chemical composition of the EN AW-AlMg4.5Mn0.7 alloy Tabela 1: Kemijska sestava zlitine EN AW-AlMg4,5Mn0,7 Chemical composition in mass fractions, w/% Si Fe Cu Mn Mg Cr Zn Ti Be Na 0.14 0.38 0.01 0.43 4.56 0.11 0.006 0.021 0.0057 0.0012 Figure 4: Thermodynamical calculation of the equilibrium-phase diagram of the investigated EN AW-AlMg4.5Mn0.7 alloy: a) polythermal section of the equilibrium-phase diagram, b) areas of temperature stability for particular phases Slika 4: Ravnotežni termodinamski izračun faznega diagrama za zlitino EN AW AlMg4,5Mn0,7: a) izopletni ravnotežni fazni diagram, b) temperaturna območja stabilnosti posameznih faz chemical analysis was taken out during the casting of an ingot with a length of about 0.5 m. There were no significant deviations of the chemical composition from the referential values prescribed by the standard EN 573-3: 2002.13 The thermodynamical calculation of the particular phase stability, along with the initial temperature of 20 °C, the pressure of 105 MPa and the specific chemical composition of the examined alloys (4.56 % Mg, 0.43 % Mn, 0.38 % Fe and 0.14 % Si), resulted in an isoplete phase diagram (Figure 4a) and an area of the temperature stability of each phase (Figure 4b). The equilibrium solidification of the EN AW-AlMg4.5Mn0.7 alloy proceeds as follows (Figure 4): primary crystals of «ai, Al6Mn and Mg2Si. Under the solidus, the AhMg2 (in the literature known as Al8Mgs) and Al3Fe phases also precipitated. It was determined that at 635 °C the primary crystals of «ai are the first to be evaluated, which corresponds to the liquidus temperature. Shortly after the evaluation of the «ai crystals at 625 °C the first eutectic phase, Al6Mn, was solidified due to a relatively high content of manganese in this alloy. The beginning of the secondary eutec-tic solidification (Mg2Si + «ai) can be predicted to occur at 581 °C. From the diagram in Figure 4a the solidus temperature of 578 °C was determined, which is associated with the maximum contribution of primary dendrites of aluminum at this temperature. A precipitation of the first phase, Al8Mgs, starts at 235 °C in the solid state. This is followed by the precipitation of the iron phase, AhFe, at 115 °C. An interpretation of these diagrams indicates a complex solidification sequence with a series of interconnected reactions. The melt is stable after the initial temperature of 650 °C to 578 °C. On the basis of the data calculated by the Thermo-Calc 5.0 software (Figure 4a) and their stability histogram (Figure 4b), an evaluation sequence can be determined as shown in Table 2. Table 2: Sequence of the microstructural-constituent evaluation made on the basis of the data calculated with the Thermo-Calc software Tabela 2: Izračunane reakcije in razvoj mikrostrukturnih sestavin pri strjevanju zlitine z uporabo programa Thermo-Calc Predicted reactions Temperature, T/°C L ^ ßAl + L' 635 Liquidus temperature, Tl L' ^ ßAl + Al6Mn + L" 625 Primary eutectic temperature, Tei L" ^ ßAl + Mg2Si 581 Secondary eutectic temperature, Te2 ßAl ^ Al8Mg5 + ßAl' 235 Precipitation temperature of the low temperature phases ßAl' ^ AhFe 115 where L' is melt composition L'; L" is melt composition L". The cooling curves of sample 6P-1 cast in a cone-shaped, grey iron-measuring cell are presented in Figure 5. The cooling curve of the sample from the cone vertex is called 6P-11, the one taken from the middle of the cone is 6P-12 and the one taken from the cone base is 6P-13. The cooling curves in Figure 5 indicate a significant mutual deviation from the values for reference temperatures of the phase changes, as well as of the curve Figure 5: Cooling curves of sample 6P-1 cast in a cone-shaped, grey iron-measuring cell Slika 5: Ohlajevalna krivulja vzorca 6P-1, ulitega v trajno stožčasto kokilo iz sive litine gradient, indicating significant differences in the cooling rates. The cooling rates of each sample were established from the cooling curves, where the temperature and the time intervals were determined from the difference between the maximum detected temperature (the pouring temperature) and the nucleation temperature established on the first derivative curve. The curve of sample 6P-13 features the least variation in temperature values, and with its smallest gradient it also has the lowest cooling rate of rc = 10.8 °C/s. Using the first and the second derivation cooling curves, the liquidus temperature Tl = 632.7 °C, the temperatures of the first and the second eutectics Tei = 607.6 °C and Te2 = 570.9 °C, as well as the solidus temperature Ts = 540.9 °C were determined. The solidification time for the cooling rate of sample 6P-13, as the difference of the times, at which the liquidus and solidus temperatures occur, amounts to Ais = 65 s. The cooling curve of sample 6P-12 indicates the cooling rate of rc = 40.3 °C/s, and here the following temperatures of the phase transitions were obtained: Tl = 634.0 °C, Tei = 594.0 °C, Te2 = 544.0 °C and Ts = 523.7 °C. There is a marked fall in all the temperatures compared to the previous cooling rate of 10.8 °C/s, except for Tl whose deviation is minimum and amounts to ~1.3 °C. In this case the solidification is completed in Ais = 11.2 s. Figure 6: Cooling curve and differential cooling curve of sample 6P-1, STA of the EN AW-AlMg4.5Mn0.7 alloy cast in the measuring cell made with the Croning process Slika 6: Ohlajevalna krivulja in odvod ohlajevalne krivulje vzorca 6P-1, STA zlitine EN AW-AlMg4,5Mn0,7, ulite v merilno celico Croning The curve of sample 6P-11 shows the cooling rate of rc = 124.0 °C/s that makes the oscillations more pronounced, and there is an uncertainty in determining the appropriate, respective phase-transition temperatures. Figure 6 shows a typical cooling curve and its first derivation of the tested sample 6P-1, STA, cast in the measuring cell made with the Croning process. On the cooling curve of the tested sample 6P-1, STA (Figure 6), there are no pronounced peaks due to a relatively low cooling rate in the measuring cell made with the Croning process of only 8.3 °C/s. By means of the first derivation of the cooling curve, the liquidus and solidus temperatures can be determined, as well as the eutectic temperatures of the tested sample. From the cooling curve of sample 6P-1, STA, it could be noted that the solidification starts at the temperature of Tl = 629.3 °C. The eutectic solidification of the melt into eutectic E1 occurs at the temperature of Tei = 598.6 °C. At Te2 = 568.8 °C the second eutectic E2 occurs. The solidification of sample 6P-1, STA, ceases at the temperature solidus of Ts = 539.3 °C, so that the obtained time of the solidification amounts to Ais = 250.1 s. The reference temperatures of the phase transformations of the samples tested with a DSC analysis (6P-1, DSC) in the measuring cell made with the Croning process (6P-1, STA), and for individual places in the Table 3: Reference temperatures of the phase changes at different cooling rates for sample 6P-1 of the EN AW-AlMg4.5Mn0.7 alloy Tabela 3: Značilne temperature faznih premen pri različnih ohlajevalnih hitrostih za vzorec 6P-1 zlitine EN AW-AlMg4,5Mn0,7 Cooling curve/ Sample indication rc/(°C/s) tl/°C te1/°C te2/°C ts/°C Ats /s TCW 0 635.0 625.0 581.0 578.0 - 6P-1, DSC 0.17 637.2 595.8 569.6 527.0 660.6 6P-1, STA 8.3 630.8 598.5 568.3 538.9 250.1 6P-13 10.8 632.7 607.6 570.9 540.9 65.0 6P-12 40.3 634.0 594.0 544.0 523.7 11.2 Figure 7: Dependences of the reference temperatures of the phase changes on the cooling rates of the EN AW-AlMg4.5Mn0.7 alloy samples Slika 7: Karakteristične temperature faznih premen zlitine EN AW-AlMg4,5Mn0,7 v odvisnosti od ohlajevalne hitrosti cone-shaped die cast (6P-13 and 6P-12), following the ascending cooling rate, are presented in Table 3. The physical models for the dependences of particular reference temperatures of the phase transformations on the cooling rates were made. Exponential types for Tl, Tei, Te2 and Ts are graphically presented in Figure 7. The liquidus temperature, Tl, is cooling-rate dependent and it covers the range of 6.4 °C. The evaluation of the primary eutectic phase Ei occurs in the temperature interval from 625.0 °C, for the equilibrium solidification, to 594.0 °C, for the cooling rate of rc = 40.3 °C/s, and with a tendency of the temperature Tei decrease. The Te2 curve has a similar trend. The largest decrease in the solidus temperature Ts was observed at the highest cooling rate. The decrease was 54.3 °C of the cooling rate at the equilibrium solidification (rc = 0 °C/s) to the maximum measured cooling rate of the sample from the middle part of the cone-shaped mould (rc = 40.3 °C/s). The deviation in Ts from the equilibrium solidification (rc = 0 °C/s) Ts = 578.0 °C to the cooling rate of rc = 0.17 °C/s (sample 6P-1, DSC, Ts = 527.0 °C/s, is the result of the formation of eutectics, Figure 7 and Table 3. Generally speaking, the liquidus temperature Tl remains almost unchanged, while the temperatures Te1, Te2 and Ts decrease with an increase in the cooling rate. The physical models for the dependences of liquidus, primary and secondary eutectic temperatures and solidus temperature were illustrated with the following equations and the corresponding correlation coefficient R2: Tl = 636.00 - 055 • rc + 0.013 • rc2 R2 = 0.73 (1) TE1 = 610.10 - 0.80 • rc + 0.010 • rc2 R2 = 0.26 (2) Te2 = 57519 - 0.51 • rc + 0.007 • rc2 R2 = 0.90 (3) TS = 552.67-154 • rc + 0.021 • rc2 R2 = 0.31 (4) The largest deviations from the obtained function curves show the temperature of the first eutectic and soli-dus temperatures that also have the minimum correlation coefficient R2. Place Mg Al Si Mn Fe O w/% x/% w/% x/% w/% x/% w/% x/% w/% x/% w/% x/% A 16.36 16.99 67.61 63.27 8.18 7.35 - - - - 7.85 12.38 B — — 65.41 79.60 — - 6.56 3.92 28.03 16.48 C 4.35 4.69 92.12 89.52 - - - - - - 3.54 5.79 Figure 8: Microstructure of sample 6P-1 obtained with a scanning electron microscope (SEM) with the marked places of quantitative analysis performed by EDS, their particular spectrums and the quantitative-analysis results (place A - black phase: Mg, Si; stoichiometry Mg2Si; place B - white phase: Al, Fe, Mn; stoichiometry Al6(Fe, Mn); place C - matrix: «Al); w/% mass fraction; x/% mole fraction Slika 8: Mikrostruktura vzorca 6P-1, posneta z vrstičnim elektronskim mikroskopom (SEM), z označenimi mesti kvantitativne analize (EDS) ter pripadajoči spektri in rezultati kvantitativne analize (mesto A - črna faza: Mg, Si; stehiometrija Mg2Si; mesto B - bela faza: Al, Fe, Mn; stehiometrija Al6(Fe, Mn); mesto C - matrica: «Al); w/% masni delež; x/% molski delež The qualitative analysis of the microstructural constituents of the EN AW-AlMg4.5Mn0.7 alloy was performed in order to determine and/or confirm the presumed stoichiometry with the energy dispersive spectrometry (EDS) for all the investigated cooling rates. An example of the quantitative phase analysis of the as-cast sample 6P-1 is shown in Figure 8. The analysis of sample 6P-1 (Figure 8) confirms the presence of the phase based on magnesium and silicon, which corresponds to the stoichiometric Mg2Si phase, defined as the second eutectic phase (