Solidus Projections Research Articles

Evolution of the Microstructure, Phase Composition and Thermomechanical Properties of the CuZnIn Alloys, Achieved by Thermally Controlled Phase Transitions

Ternary alloys with CuZnIn compositions based on the binary CuZn diagram and the modeled ternary system solidus projection were investigated. The as-cast alloys, hot-rolled sheets, and samples annealed at low temperature were examined. It was found that the α-CuZn solution phase, with minor indium additions (1–2% at.), was the primary phase crystallizing during casting and remained stable at low temperatures. The ternary phase with an approximate composition of Cu8(In,Zn)4.5 and a structure analogous to the high-temperature γ-Cu9In4 phase crystallized from the liquid state and remained stable at low temperatures. This behavior results from the stabilization against peritectoidal decomposition by the Zn atoms when substituting In in the structure. A new phase γ*-Cu9(In,Zn)4 with a modified structure was identified, characterized by a reduced unit cell and an altered electronic structure. The hot-rolling process preserves the phase composition and forms a composite-like structure, with the matrix composition of γ* and large ellipsoidal α-CuZn solution particles. On a microscale, the γ* matrix exhibited a specific structure resulting from segregation processes and was composed of micrometer-sized α-CuZn(In) solution particles and nano-sized β-CuZn phase precipitates. Low-temperature annealing intensifies the γ* matrix decomposition through binary phase precipitation.

Phase equilibria in the Al–Fe–Mo system

This paper presents the results of our comprehensive study of phase equilibria in the Al–Fe–Mo system using DTA, X-ray diffraction, SEM and electron probe microanalysis. The liquidus and solidus projections were constructed. It is shown that the ternary compound Al8FeMo3 (τ) melts congruently at >1500 °C and has a homogeneity range from 2 to 9 at.% Fe and from 23.5 to 25 at.% Mo. Isostructural phases (Mo), (αFe) and AlMo (W-type structure, cI2-Im-3m) at solidus temperatures form a continuous solid solution (αFe,Mo,AlMo). Unlike the AlMo binary phase, which is not retained by quenching, the ternary (αFe,Mo,AlMo) phase is easily quenched due to its lower decomposition temperature. Among the binary based phases, the Al8Fe5 (ε) phase has the widest homogeneity region, which extends up to 24 at.% Mo at solidus temperatures. It is shown that the addition of Mo stabilizes the Al8Fe5 (ε) phase, and the temperature of its formation in the ternary system increases to 1331 °C in contrast to 1234 °C in the binary. Moreover, according to XRD data, the Al8Fe5 (ε) phase in the ternary system has a rhombohedral structure of the Al8Cr5-type (hR78-R-3m), rather than cubic Cu5Zn8-type structure (cI52-I-43m), like the binary one. A new binary compound Al45Mo7 was identified for the first time. Its crystal structure is established as monoclinic Al45V7-type (mS104-C2/m) with the lattice parameters a = 20.534, b = 7.561, c = 10.910 Å, β = 107.33. It was shown to form by peritectic reaction L + Al5Mo ⇄ Al45Mo7 at ∼800 °C. Iron additions stabilize the Al4Mo phase, which in the binary system is stable above 942 °C.

An experimental investigation of phase transformations in the Al-Fe-V system

This paper presents a comprehensive study of phase equilibria in the Al-Fe-V system by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and electron probe microanalysis (EPMA). Liquidus and solidus projections, a number of isothermal and vertical sections, as well as a reaction scheme (Scheil diagram) are constructed. On the solidus surface, there is a continuous solid solution Al8(Fe,V)5 (Cu5Zn8-type structure, cI52-I-43 m), which decomposes with decreasing temperature. The limited solid solution formed in this case has the widest homogeneity region. At 1000 and 700 °C, the solubility of iron in it is 25 and 18 at.% Fe, respectively. The solidus surface is characterized by six three-phase fields: (Al) + Al13Fe4 + Al45V7, (Al) + Al21V2 + Al45V7, Al3V + Al23V4 + Al45V7, Al3V + Al45V7 + Al13Fe4, Al8(Fe,V)5 + Al3V + Al13Fe4 and Al8(Fe,V)5 + Al13Fe4 + Al5Fe2, which result from invariant four-phase equilibria. One of them is of the peritectic type, the others are of transition type. Equilibria take place at 653, ∼660, 735, 755, 1086, and 1121 °C, respectively. In the two-phase area AlFe + Al8(Fe,V)5 the solidus surface has a temperature minimum at 1188 °C, resulting from the invariant eutectic three-phase equilibrium L ⇄ AlFe + Al8(Fe,V)5. At ∼1080 and 730 °C, solid-state invariant four-phase equilibria Al8V5 + Al2Fe ⇄ AlFe + Al5Fe2 and Al8V5 + Al5Fe2⇄ AlFe + Al13Fe4, respectively, occur.

Investigation of the hardness and enthalpy of formation of the Sigma phase and the phase equilibria in the Cr-Co-Mn system

Phase transformations of the Cr-Co-Mn system have been studied using DTA, X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Liquidus and solidus projections, a melting diagram and Scheil reaction scheme in the whole concentration range have been constructed. Enthalpy of formation of equimolar σ phase was obtained using drop-solution calorimetry. Composition dependency of microhardness for single-phase σ alloys was obtained.

Ho–Co and Ho-Co-Fe phase diagrams

Phase equilibria in the Ho-Co-Fe ternary and the boundary binary Ho–Co systems are investigated using differential thermal analysis, scanning electron microscopy, electron-probe microanalysis, and X-ray diffraction. Based on the experimental results, the binary Ho–Co phase diagram was revised resulting in confirmation of the general features of the previously published phase diagram, except for the mode of formation of the Ho3Co compound. The temperatures of most invariant reactions were adjusted. The ternary Ho-Co-Fe phase diagram was constructed over the whole concentration range. The liquidus and solidus projections, Scheil reaction scheme and isothermal sections at 1250, 1200 and 1000 °C are presented. The most prominent feature of this system is existence of three continuous solid solutions Ho2(Co,Fe)17, Ho(Co,Fe)3 and Ho(Co,Fe)2, which define the character of the solidus projection. Other binary compounds have significant solubility of third component. Among them Ho6Fe23 has a widest homogeneity range and dissolves up to 28.0 at.% Co at all studied temperatures. All intermetallic phases are linear phases in terms of holmium. Five four-phase invariant reactions are found. One of them is of eutectic type and four ones are of U-type. Four invariant three-phase eutectic equilibria are present in the system.

Experimental investigation of the phase equilibria in the Tb-Co and Tb-Co-Fe systems and magnetic properties of phases

Phase equilibria in the Tb-Co and Tb-Co-Fe systems were investigated experimentally for the first time by a combination of scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and differential thermal analysis (DTA). Based on the experimental data from the present work, the Tb-Co system was constructed. Magnetic properties of Tb2Co17 and Tb2Co7 were measured with vibrating-sample magnetometer (VSM). The liquidus and solidus projections, the melting diagram, the isothermal sections at 1200 and 1000 °C, the vertical sections on isoconcentrates 20, 30 and 40 at% Tb and the Scheil reaction scheme for the Tb-Co-Fe system over the whole concentration range were constructed. No ternary intermetallic phase exists in the system, but the three continuous solid solutions Tb2(Co,Fe)17, Tb(Co,Fe)3 and Tb(Co,Fe)2 were found and the TbCo5 and Tb2Co7 phases have extended homogeneity ranges in the ternary system, where large amounts of Co can be substituted by Fe in both cases. The ternary Tb-Co-Fe system contains five four-phase invariant reactions encompassing one of E- and four of U-type reactions. The system also contains two three-phase invariant reactions.

Analysis of the effect of the liquid phase separation on the formation of microstructure in the Sn Fe and Al Fe Sn alloys

In the present paper, the wide miscibility gap in liquid phase in the Al-Fe-Sn system is well defined for the first time. A large miscibility gap extends from the SnFe side and dramatically extends upon addition of Al. The evolution of the microstructure during solidification was investigated experimentally in the entire concentration range in binary SnFe and ternary Al-Fe-Sn systems using SEM/EDS, XRD and DTA/DSC techniques. The existence of Fe3Sn phase in the SnFe system was confirmed. It was found that the FeAl2 phase in the ternary system participates in equilibrium with the liquid phase contrary to the binary AlFe system where it is formed in a solid state. All the binary phases do not demonstrate any essential solubility of the third component. Liquidus and solidus projections, melting diagram, isothermal section at 850 °C, vertical sections on isoconcentrates 10, 20 and 35 at.% Sn and a Scheil reaction scheme for the Al-Fe-Sn system covering the whole concentration range were constructed for the first time.

Experimental investigation of the phase equilibria in Co–Fe-Sm system with special attention to the effect of Fe substitution in structure and magnetic properties of intermetallic phases

Phase equilibria in the Sm–Co, Sm–Fe and Co–Fe-Sm systems were investigated in detail using DTA, X-ray diffraction, SEM and EPMA. Based on the experimental data from the present work, the liquidus and solidus projections, the isothermal section at 1000 °C and the Scheil reaction scheme for the Co–Fe-Sm system over the whole concentration range were constructed. The phase diagram of the Sm–Co system was revised. The Sm-rich region of the Sm–Fe system was studied for the first time. The stability domains of the intermetallic phases (binary phases and their extension inside ternary) were defined. Three continuous solid solutions Sm2(Co,Fe)17, Sm(Co,Fe)3 and Sm(Co,Fe)2 were found in the Co–Fe-Sm system at the solidus temperatures. In contrast to a previous analysis of the phase diagram for the system, wide homogeneity regions were revealed for the SmCo5 and Sm2Co7 phases and alternative invariant four-phase equilibria. The magnetic properties of samples containing Sm2(Co,Fe)17 phase were measured. The values of the Curie temperature and the magnetic moment of these samples were quite close to those earlier presented in the literature.

Phase transformations and phase equilibria in the La–Ni and La–Ni–Fe systems. Part 1: Liquidus & solidus projections

Phase equilibria in the La–Ni and La–Ni–Fe systems were studied using DTA, X-ray diffraction, SEM and EPMA. La–Ni phase diagram, liquidus and solidus projections, melting diagram and a Scheil reaction scheme for the La–Ni–Fe system over the whole concentration range were constructed. Among binary compounds LaNi5, La5Ni19 and La2Ni7 have large homogeneity ranges and dissolve at the solidus temperature up to 21.9, 16.1 and 14.0 at.% Fe, respectively. The homogeneity ranges of the remaining phases are smaller. No ternary compounds have been identified in the La–Ni–Fe system. Liquidus projection is characterized by 13 fields of primary solidification of the component-based solid solutions (γFe,Ni), (δFe), (αFe), (βLa), (γLa) and solid solutions based on binary phases LaNi5, La5Ni19, La2Ni7, LaNi3, La7Ni16, La2Ni3, LaNi, La7Ni3 and La3Ni. The solidus projection is characterized by ten three-phase fields, which result from invariant four-phase equilibria, three are of eutectic type and seven of transition type.

Experimental Investigation of Fe–Co–La System: Liquidus and Solidus Projections

Phase equilibria in the Co–Fe–La system were studied using differential thermal analysis (DTA), X-ray diffraction analysis, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Liquidus and solidus projections and a melting diagram for this system over the whole concentration range and a Scheil diagram for solidification were constructed. The ternary compound (Co,Fe)17La2 (τ) (Th2Zn17-type structure) forms by peritectic reaction L + (γCo,Fe) + Co13La ⇄ τ at 978 °C. This ternary compound is located along the isoconcentrate of 11 at.% La and extends from 45.8 to 79.3 at.% Co. The Co13La phase has the widest homogeneity region and dissolves up to 43.3 at.% Fe. The solubilities of Fe in Co5La, Co7La2, Co19La5, and Co3La2 were established to be 10.3, 9.2, 4.7, and 3.2 at.%, respectively. The solubility of Fe in Co1.7La2 and CoLa3 according to EPMA does not exceed 1 at.%. The maximum solubility of La in (γCo,Fe) and (αCo,Fe) is determined to be less than 1 at.%.

Solidus Surface of Zr-Co-Sn System

Phase transformations in the Zr-Co-Sn ternary system have been studied at crystallization using differential thermal analysis (DTA), x-ray diffraction analysis, scanning electron microscopy, and electron probe microanalysis. The solidus surface of this system over the whole concentration range is constructed for the first time, involving 20 three-phase regions. Four ternary compounds, viz. ZrCo2Sn (τ1), ZrCoSn (τ2), Zr6Co1.65Sn1.35 (τ3), and Zr5Co6Sn18 (τ4), are confirmed. It is shown that they exist at the solidus temperatures. The crystal structure of the compound τ4 is first established as Tb5Rh6Sn17-type (cF116-Fm-3m) with lattice parameter a =13.376(6) A. Only one ternary compound (ZrCo2Sn, τ1, Heusler phase) has a rather wide homogeneity range at solidus temperature (43.5–50 at.% Co along the 50Zr50Sn-Co ray). Binary compounds Zr5Sn3+x and ZrCo2 dissolve up to 9 at.% Co and 14.5 at.% Sn, respectively. All other compounds are practically linear phases. The above six phases define the character of the solidus projection, taking part in all three-phase equilibria, except for those with participation of Sn.

Experimental investigation of phase transformations in the La-Fe and La-Fe-C systems

Phase equilibria in the La-Fe-C system at crystallization were studied and the binary La-Fe system was reinvestigated using DTA, X-ray diffraction, SEM and electron probe microanalysis. Using the results, the binary La-Fe phase diagram has been redrawn and liquidus and solidus projections for the La-Fe-C system constructed, for the first time, covering the whole concentration range. There is no stable miscibility gap in the liquid phase of La-Fe system, according on our results. The La-Fe system shows a simple eutectic at 88 at.% La. The eutectic temperature was measured to be 788 °C. No intermediate phases were found. In the ternary La-Fe-C system a ternary compound La3.67FeC6 (τ) was found in equilibrium with the liquid phase and to coexist with most of the other phases in the system. Additions of carbon to La-Fe alloys caused liquid immiscibility. In this investigation, the liquid separation has been proved with clear microscopic pictures of samples showing this effect. A ternary stable liquid miscibility gap marked L1 + L2 develops from a metastable liquid miscibility gap in the La-Fe binary system. None of the binary intermetallic phases show any solubility of the third component.

Phase equilibria in the Cr-Si-Ti system below 40 at.% Si

Phase transformations in the Cr-Si-Ti ternary system have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) at silicon content <40 at.%. Partial liquidus and solidus projections and the melting diagram (solidus + liquidus) have been constructed. Some sections as partial isothermal at 1450 and 1150 °C, isopleths at 10 at.% Si and 50 at.% Ti are described. The liquidus surface is characterized by the presence of primary crystallization regions of a solid solution (Cr,βTi) and binary based phases (Cr3Si), (Ti5Si5) and the Laves-phase C14, which is stabilized by additions of silicon, and in the ternary system melts congruently above 1600 °C. The solidus surface is characterized by the presence of three-phase fields: (γTiCr2) + (Cr3Si) + (Cr,βTi), (Ti5Si3) + (γTiCr2) + (βTi,Cr) and (Ti5Si3) + (γTiCr2) + (Cr3Si). The former two regions form invariant four-phase eutectic equilibria L ↔ (βTiCr2) + (Cr3Si) + (Cr,βTi) and L ↔ (Ti5Si3) + (γTiCr2) + (βTi,Cr) at 1534 and 1243 °C, respectively. The maximum of the solidus temperature of about 1580 °C is observed in the field (γTiCr2) + (Cr,βTi). At 1495 °C the solid-state transformation (γTiCr2) + (Cr3Si) ↔ (Ti5Si3) + (Cr,βTi) takes place.

Halo Formation During Solidification of Refractory Metal Aluminide Ternary Systems

The evolution of eutectic morphologies following primary solidification has been studied in the refractory metal aluminide (Ta-Al-Fe, Nb-Al-Co, and Nb-Al-Fe) ternary systems. The undercooling accompanying solid growth, as related to the extended solute solubility in the primary and secondary phases can be used to account for the evolution of phase morphologies during ternary eutectic solidification. For small undercooling, the conditions of interfacial equilibrium remain valid, while in the case of significant undercooling when nucleation constraints occur, there is a departure from equilibrium leading to unexpected phases. In Ta-Al-Fe, an extended solubility of Fe in σ was observed, which was consistent with the formation of a halo of μ phase on primary σ. In Nb-Al-Co, a halo of C14 is formed on primary CoAl, but very limited vice versa. However, in the absence of a solidus projection it was not possible to definitively determine the extended solute solubility in the primary phase. In Nb-Al-Fe when nucleation constraints arise, the inability to initiate coupled growth of NbAl3 + C14 leads to the occurrence of a two-phase halo of C14 + Nb2Al, indicating a large undercooling and departure from equilibrium.

Experimental investigation of solidification and isothermal sections at 1000 and 1100 °C in the Al-Fe-Mn-C system with special attention to the kappa-phase

Phase equilibria in the Al-Fe-(10-20)Mn-C system upon solidification and at 1100 and 1000 °C were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. The partial liquidus and solidus projections and the isothermal sections at 1100 and 1000 °C for the Al-Fe-10Mn-C and Al-Fe-20Mn-C systems were constructed. The compound Al(Fe,Mn)3C (κ-phase) (antiperovskite structure CaTiO3-type, ≿Р5-Pm-3m) melts congruently at ∼1300 °C. The liquidus surfaces in the studied regions are characterized by the regions of primary crystallization of γ, α, κ, M3C and graphite (C). The solidus surfaces and isothermal sections at 1100 and 1000 °C of the Al-Fe-10Mn-C system in the studied region are defined by the co-existence of the κ-phase with almost all phases of the binary subsystems, except M3C: γ, α and graphite (С). The solidus surfaces and isothermal sections at 1100 and 1000 °C of the Al-Fe-20Mn-C system in the studied region are defined by the co-existence of the κ-phase with all phases of the binary subsystems, including M3C.

Investigation of phase equilibria in the Ce-Co-Fe system during solidification

Phase transformations in the Ce-Co-Fe ternary system have been studied using DTA, X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). No ternary compounds have been identified in this system. Liquidus and solidus projections and a Scheil diagram for solidification were constructed. At the solidus temperatures two continuous solid solutions form: (1) between isostoichiometric compounds Ce2Fe17 (Zn17Th2-type structure, hR57-R-3m) and Ce17Co2 (Th2Ni17-type structure, hP38-P63/mmc) and (2) between the Laves phases CeFe2 and CeCo2 (MgCu2-type structure, cF24-Fd-3m). Among the binary system-based phases, CeCo3 has the widest homogeneity region and dissolves up to 58 at% Fe at the solidus temperature. The homogeneity regions of the remaining phases are smaller. Five three-phase fields in the solidus surface result from four transition type and one eutectic invariant four-phase equilibria.

Phase equilibria in the ternary Fe-Co-S system

The Fe-FeS-CoS-Co system has been investigated experimentally from 1073K up to liquidus temperature. Samples of the system have been investigated using DTA/TGA, SEM/EDX, and XRD methods. Liquidus and solidus projections have been plotted based on experimental data.

Experimental investigation of the Al-Mn-C system. Part II: Liquidus and solidus projections

Phase equilibria upon crystallization in the Al-Mn-C system were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. The liquidus and solidus projections and the melting diagram (liquidus + solidus) for this system were constructed covering the whole concentration range. The ternary compound Mn3AlC (κ) (antiperovskite structure CaTiO3-type, ≿Р5-Pm-3m) melts congruently at 1320 °C. The liquidus surface consists of the binary compounds, the ternary compound Mn3AlC (κ) and solid solutions primary crystallization fields. The carbide Mn5C2 in the ternary system participates in equilibrium with the liquid phase in contrary to the binary system where it is formed from the solid state equilibrium. The solidus surface of the Al-Mn-C system in the region up to 50 at.% Al is defined by the co-existence of the κ-carbide with almost all phases of the binary subsystems: (С), (γMn), (εAlMn), (Al4C3), (Mn7C3) and (Mn5C2). The solidus surface in the region >45 at.% Al is defined by the co-existence of the carbide Al4C3 with all phases from Al-rich region.The DTA curves of the alloys with compositions close to the homogeneity region of phase (εAlMn), exhibit (on heating) an exothermic effect at ∼570 °C. This exothermic effect corresponds to the formation of the ordered metastable τ-phase, which is formed by mechanism: ε → ε' (B19) → τ. τ-phase (AuCu, tP2-P4/mmm, a = 2.760, c = 3.600 Å) and which was observed in the alloys after heating up to 700 °C and slow cooling (5 °C/min).

Isothermal section of the Ti–Ga–Sn system at 1300°C

Phase equilibria at 1300 °C in the Ti–Ga–Sn system in the concentration interval 50–100 at.% Ti were studied by the methods of X–ray diffraction (XRD), scanning electron microscopy (SEM) and electron microprobe analysis. The partial isothermal section at 1300 °C was constructed. A ternary compound Ti5GaSn2 (τ), found by us previously, was confirmed in this section (1300 °C). The phase locates along the isoconcentrate 62.5 at.% Ti and extends from 4.5 till 28 at.% Ga. The lattice parameters of the phase were calculated in a tetragonal Nb5SiSn2–type structure with the values: a = 10.579(3)–10.307(1), c = 5.310(2)–5.106(1) Å. The binary based phase Ti5Ga3 also locates along the isoconcentrate 62.5 at.% Ti due to mutual substitution of the Sn and Ga atoms. D88–type compounds Ti5Sn3 and Ti5Ga4 form a continuous solid solution, denoted Ti5(Sn,Ga)3-4. Ga-poor part of it (below ∼12.5 at.% Ga) forms by an interstitial mechanism, while in the interval above ∼12.5 at.% Ga it is a substitution phase. The Sn and Ga atoms substitute each other. Isostructural Ti2Sn and Ti2Ga at 1300°С do not form a continuous solid solution, in contrast to the solidus projection. Solubility of Ga in Ti3Sn and Ti2Sn is 13.5 and 2 at.%, respectively. Solubility of Sn in Ti2Ga and Ti5Ga3 is 14 and 6 at.%, respectively.At 1300 °C ternary compound τ coexists with all the phases based on binary compounds of the border systems (Ti3Sn, Ti2Sn, Ti2Ga, Ti5Ga3, Ti5(Sn,Ga)3-4). The isothermal section at 1300°C in the concentration interval studied is characterized by six three-phase fields: (βTi) + (Ti3Sn) + (Ti2Ga), τ + (Ti3Sn) + (Ti2Sn), τ + (Ti2Sn) + Ti5(Sn,Ga)3-4, τ + (Ti3Sn) + (Ti2Ga), τ + (Ti2Ga) + (Ti5Ga3) and τ + (Ti5Ga3) + Ti5(Sn,Ga)3-4.

Experimental Liquidus Surface Projection of the Ni-Ru-Zr System

SEM with EDX and XRD analyses were used to study 21 as-cast Ni-Ru-Zr alloys. Phases were distinguished by BSE image contrast, and the primary phases were determined by their dendritic morphology, with the solidification sequences derived from the microstructure. Identification of the phases was done by EDX analyses, and they were verified by XRD. From these analyses, the solidus and liquidus surface projections were drawn. Three ternary phases were found: τ1 of composition ~Zr24Ru22Ni44 (at.%), τ2 at ~Zr74Ru4Ni22 (at.%), and τ3 at ~Zr35Ru3Ni62 (at.%). Sixteen invariant reactions were identified, and the largest liquidus surface was for ~ZrRu.