COMPUTATION OF LIQUIDUS OF THE Al Fe Mn Ni Si SYSTEM IN THE RANGE OF ALUMINUM-NICKEL ALLOYS (NICKALINS)

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1 Metal Science and Heat Treatment, Vol. 56, Nos. 3 4, July, 2014 (Russian Original Nos. 3 4, March April, 2014) UDC COMPUTATION OF LIQUIDUS OF THE Al Fe Mn Ni Si SYSTEM IN THE RANGE OF ALUMINUM-NICKEL ALLOYS (NICKALINS) A. A. Amenova, 1 N. A. Belov, 2 and D. U. Smagulov 2 Translated from Metallovedenie i Termicheskaya Oraotka Metallov, No. 3, pp , March, The ThermoCalc software is used to plot the projections of liquidus in characteristic sections of the Al Ni Fe Mn Si system as applied to aluminum-nickel alloys (nickalins). Key words: aluminum-nickel alloys, liquidus, eutectic, primary crystals, intermetallic phases. INTRODUCTION Aluminum alloys ased on a Ni-containing eutectic (nickalins) and alloyed exceptionally with transition metals according to the principles presented in [1] possess a higher comination of casting and mechanical properties (at high temperatures inclusive) than silumins. The most alanced set of properties has een implemented in alloy AN4Mts2 containing 4% Ni [4, 5]. However, this nickalin, where the whole of nickel enters the (Al) + Al 3 Ni eutectic [(Al) is used for the aluminum solid solution], should e treated as a model composition, ecause it is characterized y a low iron content, i.e., its production requires high-purity aluminum. The main disadvantages of alloy AN4Mts2 have een eliminated in the newly developed (at the department of casting technology of the NITU MISiS ) sparingly alloyed AN2ZhMts nickalin ased on the Al Ni Fe Mn system [6]. The content of nickel in this alloy has een reduced y aout a factor of two, and iron is an alloying component rather than an impurity, ecause the the main structural component of the metal is an (Al) + Al 9 FeNi eutectic. To reinforce the aluminum matrix the alloy also contains additives of Zn and Mn segregated in the form of dispersoids in the annealing process. Zirconium does not enter phases other than Al 3 Zr, wheres manganese may e distriuted in several phases, which requires a special analysis. It follows that the ase system for the AN2ZhMts alloy is Al Ni Fe Mn Si (with allowance for inevitale admixture of silicon). As applied to the group of alloys considered, this five-component system contains eight phases, namely, Al 3 Ni, Al 3 Fe, Al 6 (Fe, Mn), Al 9 FeNi, Al 8 Fe 2 Si, Al 15 (Fe, Mn) 2 Si 3,Al 3 FeSi, 1 K. I. Satpaev Kazakh National Technical University, Almaty, Kazakhstan. 2 National University of Science and Technology MISiS, Moscow, Russia ( nikolay-elov@yandex.ru). and (Si). Their characteristics and rief notation are given in Tale 1. It has een shown earlier that the presence of primary crystals of excess phases (of intermetallics in particular) in the structure of nickalins is undesirale, ecause the latter have a coarse morphology (Fig. 1) that may affect the mechanical properties. The adaptaility of aluminum-matrix composites to manufacture y impregnation is also affected negatively y primary intermetallics. Determination of the concentration oundaries of these crystals in inary and ternary systems presents no difficulty (with the use of the appropriate phase diagrams), while the graphical method is virtually inapplicale to four-component and more complex systems. Therefore, it is expedient to resort to special softwares, like the Thermo-Calc one, for designing multicomponent systems including aluminum-ase ones, as it has een shown in [7]. In the present work we had an aim (1) to apply the Thermo-Calc software (file TTA15) for computing and plotting the liquidus projections in the most characteristic sec- TABLE 1. Characteristics of Phases Present in Alloys of the Al Ni Mn Fe Si System [7 12] Formula Notation Composition, wt.% Density, g cm 3 Si (Si) 100 Si 2.3 Al 3 Fe Al 3 Fe 37 Fe 3.90 Al 6 (Fe, Mn) Al Mn, Fe Al 3 Ni Al 3 42 Ni 3.95 Al 5 FeSi Al Fe, Si 3.45 Al 8 Fe 2 Si Al Fe,6 13Si 3.58 Al 9 FeNi Al Fe,18 28Ni 3.4 Al 15 (FeMn) 3 Si 2 Al Fe,1.5 29Mn, 8 13Si /14/ Springer Science + Business Media New York

2 138 A. A. Amenova et al. tions of the Al Ni Fe Mn Si system in the concentration ranges of 0 9% Ni, 0 3% Fe, 0 3% Mn, 0 3% Si (in wt.%) and (2) to apply the results otained for determining the optimum concentrations of Ni, Fe, Mn and Si in sparingly alloyed nickalins. RESULTS AND DISCUSSION 50 m 10 m Fig. 1. Typical morphology of primary crystals of intermetallic phases Al 6 (Fe, Mn) (a) and Al 9 FeNi ( ) in alloys of the Al Fe Mn Ni Si system: a) 2% Ni, 0.5% Fe, 1.5% Mn, 0.1% Si, sand casting, SEM; ) 4% Ni, 1% Fe, 0.1% Si, chill casting, SEM. Computation of Liquidus for the Al Ni Fe, Al Ni Mn and Al Ni Si Ternary Systems In the first stage we computed the solidus and liquidus projections for the Al Ni Fe, Al Ni Mn and Al Ni Si ternary systems. The computed values were compared with reference data for estimating the reliaility of the former. It can e seen from Fig. 2a that the computed lines of the oundaries of primary crystallization of phases (Al), Al 3 Ni, Al 3 Fe and Al 9 FeNi virtually correspond to the accepted structure of the phase diagram of the Al Ni Fe system [7, 8, 10]. Specifically, the parameters of points P (650 C) and E (640 C) matching the peritectic (L +Al 3 Fe (Al) + Al 9 FeNi) and euetctic (L (Al) + Al 9 FeNi + Al 3 Ni) reactions are quite close. Computation of the solidus close to the aluminum angle also gives a quite reliale result (Fig. 2 ). It also follows from Fig. 2 that the soluilities of iron and nickel in (Al) are quite low and approximately equal to the values for the inary Al Ni and Al Fe systems [8]. In the Al Ni Mn system the computation of the liquidus projection shows that growth in the nickel content to the eutectic concentration (aout 6%) shifts the oundary of the appearance of primary crystals of phase Al 6 Mn from 2 to 1.4% (Fig. 2c ). The concentration of manganese in (Al) in the presence of nickel decreases from 1.4 to 1.25% (Fig. 2d ). It should e noted that according to Mondolfo [8] the aluminum angle of this system in equilirium with (Al) can contain a ternary Al 3 MnNi compound in addition to the inary aluminides (Al 3 Ni and Al 6 Mn). However, this compound is asent in the TTAL5 file. Taking into account the inconsiderale numer of pulications mentioning the presence of the ternary compound, we chose the variant when only inary intermetallics can e in equilirium with (Al). In contrast to iron and manganese, silicon shifts the oundary of the appearance of primary crystals of phase Al 3 Ni toward higher nickel contents. It can e seen from Fig. 2e that at 3% Si it attains 7% Ni (as compared to 6% in the inary Al Ni system). The limiting soluility of Si in (Al) decreases somewhat in the presence of nickel (Fig. 2f ). In the Al Ni Si and more complex systems silicon does not form compounds with nickel [7, 8, 12]. On the whole, with allowance for the known data, computation of the ternary systems in the region of the aluminum angle gives quite correct results. This means that the thermodynamic TTAl5 file may e used for computing more complex systems. Computation of Liquidus for the Quaternary Al Ni Fe Mn System At a low concentration of silicon admixture we should consider the Al Ni Fe Mn system for analyzing the phase composition of nickalins. The pairwise action of nickel, manganese and iron on the oundaries of primary crystallization of intermetallic phases in this quaternary system at a constant concentration of one of the components is presented in Fig. 3. At 0.2% Fe the range of primary crystallization of (Al) widens to 5% Ni and 1.25% Mn (Fig. 3a ). For growth in the content of manganese we should expect the appearance of primary crystals of phase Al 6 (Fe, Mn), whereas growthin the nickel content should e accompanied y formation of Al 9 FeNi. An Al 3 Ni phase can form only when the nickel content exceeds 8%. At 1% Fe the range of primary crystallization of (Al) is reduced sustantially, i.e., to 2.6% Ni and 0.76% Mn (Fig. 3 ). It should e noted that at such increase in the concentration of iron (from 0.2 to 1%) the minimum liquidus temperature [at the point of ternary eutectic L (Al) + Al 9 FeNi + Al 6 (Fe, Mn)] increases from 642 to 649 C. The joint action of iron and nickel at a constant concentration of manganese is presented in Fig. 3c and d ). Just like in the previous case, growth in the concentration of manganese causes narrowing of the range of primary crystallization of (Al). At 0.5% Mn the excess iron causes the appearance of

3 Computation of Liquidus of the Al Fe Mn Ni Si System in the Range of Aluminum-Nickel Alloys 139 P (650 C) E (640 C) Al Mn 6 c d e f Fig. 2. Projections of liquidus (a, c, e) and solidus (, d, f ) surfaces of the ternary systems: a, )Al Ni Fe; c, d )Al Ni Mn;e, f )Al Ni Si. phase Al 3 Fe (Fig. 3c ), while at 1% Mn phase Al 6 (Fe, Mn) appears (Fig. 3d ). In oth cases the appearance of primary crystals of phase Al 3 Ni is possile only at a low concentration of iron. A larger part of the liquidus surface in the considered range of concentrations of this quaternary system is taken y phase Al 6 FeNi. It should e noted that in the section with 0.5% Mn the location of the fields of primary crystallization of intermetallic phases is quite close to the location of the corresponding fields in the Al Ni Fe ternary system (see Fig. 2a ).

4 140 A. A. Amenova et al. E (640 C) c d e f Fig. 3. Projections of liquidus and solidus surfaces in sections of the Al Ni Mn Fe system: a) at 02% Fe; )at1%fe;c) at 0.5% Mn; d )at1%mn;e)at2%ni;f )at4%ni. The oundaries of primary crystallization at a constant concentration of nickel are presented in Fig. 3e and f. At 2 and 4% Ni they have a qualitatively similar form [in the range considered the crystallization of (Al) can e accompanied y primary crystallization of Al 9 FeNi, Al 6 (Fe, Mn) and Al 3 Fe)] ut differ in the sizes of the region of primary crystallization of (Al); at 4% Ni it is sustantially smaller. Comparing Figs. 2 and 3 we should note that the minimum liquidus temperature in the Al Ni Fe Mn system is aout 640 C, which matches the eutectic reactions L

5 Computation of Liquidus of the Al Fe Mn Ni Si System in the Range of Aluminum-Nickel Alloys 141 E (640 C) c d e f Fig. 4. Projections of the liquidus surface in sections of the Al Ni Mn Fe Si system: a) at 4% Ni and 0.2% Fe; ) at 4% Ni and 1% Mn; c) at 4% Ni and 0.5% Si; d ) at 2% Ni and 0.5% Si; e) at 1% Ni and 0.5% Si; f ) at 1% Ni and 1% Mn. (Al) + Al 9 FeNi + Al 3 Ni (Fig. 2a, Fig. 3c and d ) and L (Al) + Al 9 FeNi + Al 6 (Fe, Mn) (Fig. 3a ). The effect of manganese on this temperature is inconsiderale. Computation of Liquidus for the Five-Component Al Ni Fe Mn Si System In accordance to the data presented in Tale 1, silicon in the Al Ni Fe Mn Si system can enter four phases, ut

6 142 A. A. Amenova et al. only one of them (Al 15 (FeMn) 3 Si 2 ) can crystallize primarily in the concentration range in question. Specifically, at 4% Ni and 0.2% Fe the concentration of Si should exceed 1.5% (Fig. 4a ). At a lower concentration of silicon the excess manganese should cause formation of primary crystals of phase Al 6 (Fe, Mn). At a low concentration of manganese the oundary of the appearance of primary crystals of Al 15 (FeMn) 3 Si 2 increases (over 3% Si). The minimum liquidus temperature in this section is 637 C, which matches a eutectic reaction L (Al) + Al 15 (FeMn) 3 Si 2 +Al 6 (Fe, Mn). This temperature is not much lower than in the Al Ni Fe Mn system (see aove), ut the silicon concentration is 1.74% (Fig. 4a ), which exceeds the range of nickalin compositions [1 7]. At 4% Ni and 1 % Mn primary crystals of phase Al 15 (FeMn) 3 Si 2 appear at at least 2% Si even at 1 2% Fe (Fig. 4 ). The minimum liquidus temperature in this section is 638 C, which matches a eutectic reaction L (Al) + Al 15 (FeMn) 3 Si 2 +Al 9 FeNi. According to the data of Fig. 4, formation of primary crystals of phase Al 6 (Fe, Mn) in this section is impossile, Figure 4c e reflect the joint action of iron and manganese at 0.5% Si and different concentrations of nickel. At 4% Ni phase Al 15 (FeMn) 3 Si 2 cannot crystallize as a primary one, ecause the excess of manganese provides formation of only Al 9 FeNi, Al 9 (Fe, Mn) and Al 3 Fe in the fields of primary crystallization (Fig. 4c ). Lowering of the concentration of nickel to 2% at the same concentration of silicon does not affect the qualitative location of these fields. However, the range of primary crystallization of (Al) widens sustantially toward increase in the concentration of iron (Fig. 4d ). At 1% Ni the field of primary crystallization of phase Al 9 FeNi disappears and the sizes of the range of primary crystallization of (Al) change inconsideraly (Fig. 4e). Note that the maximum permissile concentration of iron in the given section attains 1.75% in the asence of manganese and 1.6% at 0.5% Mn. When the concentration of manganese exceeds 0.5%, the concentration of iron decreases consideraly. Figure 4f shows the joint action of iron and silicon at 1% Ni and 1% Mn; a field of primary crystallization of phase Al 9 FeNi is also asent. We should expect the appearance of primary crystals of phase Al 6 (Fe, Mn); for this, it is sufficient to have 0.8% Fe. Generalizing the results of the computation we should mention the complex influence of the composition of the alloys on the sizes of the region of primary crystallization of the aluminum solid solution and on the intermetallic that can appear in the structure in the form of primary crystals. CONCLUSIONS 1. We have used the Thermo-Calc software (the TTAl5 file) to plot liquidus projections on characteristic sections of the Al Ni Fe Mn Si system in the range of concentrations of 0 9Ni,0 3Fe,0 3Mn,and0.3Si(inwt.%). 2. In this range of concentration of the elements studied primary crystallization yields phases Al 9 FeNi, Al 6 (Fe, Mn), Al 3 Fe, Al 15 (FeMn) 3 Si 2, and Al 3 Ni. The first three phases should form in the range of nickalin compositions with the highest proaility. Their formation depends consideraly on the proportion of nickel, iron and manganese. The other phases can get into the fields of primary crystallization only at elevated concentrations of silicon and nickel, namely, over 2% Si for Al 15 (FeMn) 3 Si 2 and over 6% Ni for Al 3 Ni. 3. With growth of the nickel concentration the maximum permissile concentration of iron at which primary crystals of intermetallic phases do not form decreases sustantially. Specifically, at 1% Ni and 0.5% Si it attains 1.75%, while at 4% Ni and 0.5% Si it is only 0.65%. 4. The minimum liquidus temperature in the asence of silicon is aout 640 C, which matches a eutectic reaction L (Al) + Al 9 FeNi + Al 6 (Fe, Mn). The effect of manganese on this temperature is inconsiderale. REFERENCES 1. N. A. Belov, Principles of optimising the structure of creep-resisting casting aluminum alloys using transition metals, J. Adv. Mater., 1(4), (1994). 2. N. A. Belov and V. S Zolotarevskii, Castale alloys ased on an aluminum-nickel eutectic (nickalins) as a possile alternative to silumins, Tsvetn. Met., No. 2, (2003). 3. N. A. Belov and A. N. Alain, Promising aluminum alloys with enhanced heat resistance for fitment purposes as a possile alternative to steels and cast irons, Armaturostroenie, No. 2, (2010) 4. N. A. Belov, A castale aluminum-ase alloy, RF Patent No , Pul , Byull. Izor. Polezn. Modeli, No (1993). 5. V. S. Zolotarevskii and N. A. 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