Phase equilibria of the Ti-Ga-Sn system have been determined at primary crystallization and at 1000 °C in the composition interval 50-100 at.

The ternary phase diagram Ti-Co-Sn was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Isothermal sections at 1000 and 1200 degree celsius have been determined experimentally for the first time in the entire range of compositions. Thirteen and ten three-phase regions were found at 1000 degree celsius and 1200 degree celsius, respectively. Vertical sections at 10, 20 and 30 at.% Sn were plotted. The most striking feature of the ternary Ti-Co-Sn phase diagram is formation of a ternary compound TiCo2Sn (Heusler phase, tau), which was found at both investigated temperatures. The TiCoSn compound (half-Heusler phase) was not found. Among binary compounds, Ti5Sn3 and TiCo have the widest homogeneity regions. The Ti5Sn3 phase dissolves 10.0 and 9.8 at.% Co at 1200 and 1000 degree celsius, respectively, forming an interstitial solid solution. The solubility of Sn in TiCo is more than 10 at.% at both 1200 and 1000 degree celsius. The remaining binary intermetallic phases hardly dissolved the third component. The liquid phase at 1000 degree celsius mainly exists in the Sn-rich corner, while at 1200 degree celsius it stretches along Co-Sn side spreading from the Sn corner and is also present on the Ti-rich side. In addition, two four-phase invariant transition type reactions TiCo2 (h) + (alpha Co) reversible arrow tau + TiCo3 and TiCo + TiCo2 (h) reversible arrow tau + TiCo2 (c) were deduced.

In the present paper, the Al–Fe-Mo phase diagram was studied by X-ray diffraction (XRD), differential thermal analysis, differential scanning calorimetry, scanning electron microscopy and electron probe microanalysis. For the first time, isothermal sections at 1450, 1300 and 1200 °C were experimentally determined over the entire range of compositions. A ternary intermetallic compound τ (Mo3FeAl8) with a TiAl3-type structure was observed at all above temperatures. It has been shown that isostructural disordered bcc (A2) phases of pure elements Fe and Mo (W-type structure, cI2- Im3 m) in the ternary system at 1450 °C form a continuous solid solution (Mo,Fe,Al), dissolving up to 50 at.

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 degrees 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 degrees C, respectively. In the two-phase area AlFe + Al8(Fe,V)5 the solidus surface has a temperature minimum at 1188 degrees C, resulting from the invariant eutectic three-phase equilibrium L reversible arrow AlFe + Al8(Fe,V)5. At -1080 and 730 degrees C, solidstate invariant four-phase equilibria Al8V5 + Al2Fe reversible arrow AlFe + Al5Fe2 and Al8V5 + Al5Fe2 reversible arrow AlFe + Al13Fe4, respectively, occur.

The phase diagrams of the Er-Co-Fe ternary system, as well as boundary binary Er-Co and Er-Fe systems, were plotted using differential thermal analysis, powder x-ray diffraction, metallography, and electron probe microanalysis. Binary Er-Co and Er-Fe phase diagrams were revised. All invariant temperatures were updated and all disagreements between previously reported results were resolved. For the first time liquidus and solidus projections, isothermal sections at 1250, 1200 and 1000 °C of the Er-Co-Fe system in the entire range of concentrations, and the reaction scheme (Scheil diagram) were constructed. Three continuous solid solutions Er2(Co,Fe)17 (Th2Ni17-type structure, hP38-P63/mmc), Er(Co,Fe)3 (PuNi3-type structure, hR36-R-3m) and Er(Co,Fe)2 (MgCu2-type structure, cF24-Fd-3m) were found to exist at all investigated temperatures. At solidus temperatures, the Er6Fe23 compound dissolves up to 37.5 at.

Phase equilibria in the Ho-Co-Fe ternary and the boundary binary Ho-Co systems are investigated using dif-ferential 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 degrees 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 temper-atures. 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.

Phase equilibria at 1300 degrees C in the TieGaeSn 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 degrees C was constructed. A ternary compound Ti5GaSn2 (tau), found by us previously, was confirmed in this section (1300 degrees 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) angstrom The binary based phase Ti5Ga3 also locates along the isoconcentrate 62.5 at.% Ti due to mutual substitution of the Sn and Ga atoms. D8(8)-type compounds Ti5Sn3 and Ti5Ga4 form a continuous solid solution, denoted Ti-5(Sn,Ga)(3-4). Ga-poor part of it (below similar to 12.5 at.% Ga) forms by an interstitial mechanism, while in the interval above similar to 12.5 at.% Ga it is a substitution phase. The Sn and Ga atoms substitute each other. Isostructural Ti2Sn and Ti2Ga at 1300 degrees C. 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 degrees C ternary compound tau coexists with all the phases based on binary compounds of the border systems (Ti3Sn, Ti2Sn, Ti2Ga, Ti5Ga3, Ti-5(Sn, Ga) 3-4). The isothermal section at 1300 degrees C in the concentration interval studied is characterized by six three-phase fields: (beta Ti) + (Ti3Sn) + (Ti2Ga), tau + (Ti3Sn) + (Ti2Sn), tau + (Ti2Sn) + Ti-5(Sn, Ga) 3-4, tau + (Ti3Sn) + (Ti2Ga), t + (Ti2Ga) + (Ti5Ga3) and tau + (Ti5Ga3) + Ti-5(Sn, Ga)(3-4). (C) 2016 Elsevier B.V. All rights reserved.

Phase equilibria in the Ti-Dy-Al system in the Ti-TiAl-DyAl2-Dy region at 850 degrees C were studied by the methods of X-ray diffraction, SEM and electron microprobe. The isothermal section at this temperature was constructed. The ternary compounds in the studied region were not found. The isothermal section at 850 degrees C is characterized by the three-phase regions alpha(1) + (alpha Dy) + (Dy2Al), alpha(1) + alpha(2) + (DY2Al), alpha(2) + (DY2Al) + (Dy3Al2), alpha(2) + (Dy3Al2) + (alpha DyAl2), (DyAl) + (alpha DyAl2) + (Dy3Al2) and alpha(2) + (alpha DyAl2) + gamma and appropriate two-phase areas. (C) 2014 Elsevier B.V. All rights reserved.

By the methods of X-ray diffraction, SEM and electron probe microanalysis, phase equilibria in the Ti-Dy-Sn system below 40 at.% Sn at temperatures 1400, 1100 and 900 degrees C were studied. The isothermal sections at 1400, 1100 and 900 degrees C were constructed. It was shown that the ternary compound Ti4.2-4.3 Dy0.8-0.7Sn <=(3) (tau) is stable at these temperatures. At 1400 degrees C the liquid phase is present in the system. The isothermal section at this temperature is characterized by the three-phase regions L + (beta Ti) + (Dy5Sn3), (beta Ti) + (Ti3Sn) + (Dy5Sn3), (Ti3Sn) + tau + (Dy5Sn3), (Ti3Sn) + tau + (Ti2Sn) and (Ti2Sn) + tau + (Ti5Sn3) and appropriate two-phase fields. At 1100 and 900 degrees C the liquid phase is absent, instead the three-phase field (beta Ti) + (alpha Dy) + (Dy5Sn3) appears. Other three-phase fields exist at all the temperatures studied. The isothermal sections at 1100 and 900 degrees C by their character are similar to the solidus surface. (c) 2013 Elsevier B.V. All rights reserved.

Abstract Phase equilibria in the Ti–Dy–Sn system below 40 at.% Sn were studied using differential thermal analysis, X-ray diffraction, metallography and electron microprobe. The partial liquidus and solidus projections and the melting diagram (liquidus + solidus) were constructed. A new ternary compound τ with composition Ti4.2–4.3Dy0.8–0.7Sn≲3, found by us previously, melts congruently above 1 543 °C and coexists with all the phases based on the binary compounds of the boundary binaries in the concentration interval studied. The liquidus surface is characterized by primary crystallization regions of (βTi), (βDy), (αDy), (Ti3Sn), (Ti2Sn), (Ti5Sn3), (Dy5Sn3) and τ. Five three-phase fields in the solidus surface result from three eutectic and two transition type invariant four-phase equilibria: LE1 ⇄ (βTi) + (Ti3Sn) + (Dy5Sn3), LE2 ⇄ (Ti3Sn) + τ + (Dy5Sn3), LE3 ⇄ (βTi) + (αDy) + (Dy5Sn3), LU1 + (Ti2Sn) ⇄ (Ti3Sn) + τ and LU2 + (Ti2Sn) ⇄ (Ti5Sn3) + τ at 1 524, 1 500, 1 150, 1 543 and 1 498 °C, respectively. In the two-phase areas (βTi) + (Dy5Sn3), (Ti3Sn) + (Dy5Sn3), (Ti2Sn) + τ and τ + (Dy5Sn3) the solidus surface has the temperature maxima at 1 620, 1 540, > 1 543 and > 1 500 °C, respectively.

The phase equilibria in the Ti–Ti5Si3–Dy5Si3–Dy part of the Ti–Dy–Si system were studied by DTA, X-ray diffraction, metallography and EPMA. The melting diagram, isopleths at 5Si, 65Ti and 65Dy, and a reaction scheme were constructed. The solidus surface is characterized by the following three-phase fields: 〈β-Ti〉+〈Ti5Si3〉+〈TiDySi〉, 〈β-Ti〉+〈TiDySi〉+〈α-Dy〉, 〈TiDySi〉+〈α-Dy〉+〈Dy5Si3〉, and 〈Ti5Si3〉+〈TiDySi〉+〈Dy5Si3〉. The first two fields form via U-type equilibria, L+〈Ti5Si3〉⇄〈β-Ti〉+〈TiDySi〉 and L+〈β-Ti〉⇄〈TiDySi〉+〈α-Dy〉, at 1320 and 1170°C, respectively. The third three-phase field results from an invariant eutectic four-phase equilibrium, L⇄〈TiDySi〉+〈α-Dy〉+〈Dy5Si3〉, at 1157±6°C. The fourth one is the result of a P-type equilibrium, L+〈Ti5Si3〉+〈Dy5Si3〉⇄〈TiDySi〉. The temperature of the latter was estimated to be within the interval 1650–1700°C.

A prediction of the Ti-Dy phase diagram was given, according to which the system is of eutectic type with the eutectic coordinates ∼1270°C and 82at.% Dy. Experimental verification on the two key-alloys confirmed the type of system, as well as the eutectic coordinates. The last were established to be 1280°C and 82at.% Dy. The eutectic is fine with a grain size of about 0.2μm. The hypo-eutectic alloy 95Ti-5Dy showed high plasticity at contraction that is on the level of pure titanium. The Ti-Dy system is proposed as a basis of composite materials of eutectic type.

Phase equilibria in Ti-rich corner of the Ti-Si-Sn-Al system were studied using differential thermal analysis, X-ray diffraction, microscopy, and electron microprobe analysis. Projections of solidus and liquidus surfaces, an isothermal section at 1300°C and an isopleth at 9Si-1Sn (at.%) were constructed. It was shown that in the concentration interval studied at the solidus and 1300°C temperatures two two-phase Ti5(Si,Sn,Al)3 + <β-Ti< and Ti5(Si,Sn,Al)3 + <α-Ti< regions are present. The liquidus surface is characterised by the regions of β and Z primary crystallisation, resulting in bivariant L ↔ β + Ti5(Si,Sn,Al)3 eutectic. The character of horizontal and vertical sections is similar to that for the Ti-Si-Al system.

By the methods of X-ray, microscopic and electron microprobe analysis the phase compositions of Ti-rich as-cast Ti-Si-Sn-Al alloys were studied. Projections of the solidus and liquidus surfaces at three Si/Sn ratios (9Si-1Sn, 7Si-3Sn, 5Si-5Sn in at.%) are discussed. The projections are similar to that for the Ti-Si-Al system, and differ in the width of the homogeneity range of the coexisting phases. Microhardness of the constituents (transformed beta-Ti, Ti-5(Si, Sn, Al)(3) (Z) and eutectic (beta + Z) was measured. The results are discussed on the basis of the above projections. Long-term and hot hardness of the alloys were examined. They strongly depend on the relative tin content in the alloys. All the alloys studied show higher strength at elevated temperature than VT-18 alloy. The alloy 75Ti-5Si-5Sn-15Al seems to be prospective in respect to workability.