Phase relations in the Nd–Al–Si system at 500°C

Journal of Thermal Analysis and Calorimetry, 2012

The isothermal section at 500°C of the Dy-Al-Si system was studied in the whole concentration range. The alloys were characterized by X-ray powder diffraction, scanning electron microscopy and electron micro-probe analysis. A few samples were analysed by differential thermal analysis. The following intermetallic compounds, some of them showing variable composition, were found: DyAl 2 Si 2 (s 1), hP5-CaAl 2 O 2 structure type, Dy 2 Al 3 Si 2 (s 2) mS14-Y 2 Al 3 Si 2 structure type, Dy 2 Al 1?x Si 2-x (s 3), 0 B x B 0.25, oI10-W 2 CoB 2 structure type and Dy 6 Al 3 Si (s 4), tI80-Tb 6 Al 3 Si structure type. A number of binary phases dissolve the third element forming ternary solid solutions: Dy(Al 1-x Si x) 3 , 0 B x B 0.5, hP16-Ni 3 Ti structure type, Dy(Al x Si 1-x) 2 , 0 B x B 0.1, oI12-GdSi 2 structure type, Dy(Al x Si 1-x) 1.67 , 0 B x B 0.2, oI12-GdSi 2 structure type, DyAl x Si 1-x , 0 B x B 0.2, oC8-CrB, and Dy 5 (Al x Si 1-x) 3 , 0 B x B0.3, hP16-Mn 5 Si 3 structure type. The melting point of Dy 6 Al 3 Si was determined.

Intermetallics, 1999

The Al±Ni±Ti phase diagram has been thermodynamically assessed and a consistent set of thermodynamic functions has been developed. The thermodynamic modeling is based on an experimental investigation of the phase equilibria in the composition range of 0.14x Al 40.7. Alloys were prepared by argon-arc or vacuum-electron beam melting of elemental powder blends. X-ray powder diraction, metallography, SEM and EMPA-techniques were employed to analyze the samples in the as-cast state as well as after annealing at 800, 900 and 1000 C. The existence of the four ternary compounds, (1 to (4 , has been con®rmed, although homogeneity regions dier signi®cantly from reports in the literature. The homogeneous phase, previously claimed at ``Al 23 Ni 26 Ti 51 '', is shown by high resolution microprobe and X-ray diraction measurements to be an extremely ®ne-grained eutectic structure. The congruent melting behavior of (4 elxi 2 i is con®rmed, but, in contrast to earlier reports, primary crystallization and congruent melting have been observed for (1 el 13 xi 2 i 5 and (3 el 3 xii 2. In contrast to earlier assessments, (1 Y(2 and (3 are experimentally found to be stable at 800, 900 and 1000 C. The thermodynamic modeling of the ternary phases (2 and (3 is done with sim-pli®ed sublattice models, considering their crystal structure and homogeneity ranges. The sublattice model for (4 is taken from an earlier asessment of the nickel-rich ternary phase equilibria. The present assessment covers the entire composition range. An application to the solidi®cation behavior of ternary alloys is also exempli®ed.

Intermetallics, 1999

Phase relations in the ternary system Al±Ni±Ti have been experimentally established for the isothermal section at 900 C for concentrations 0.1 4 x Al 4 0.7. The investigation is based on X-ray powder diraction, metallography, SEM and EMPA-techniques on about 40 ternary alloys, prepared by argon-arc or vacuum-electron beam melting of proper elemental powder blends. The existence of four ternary compounds, t 1 to t 4 , is con®rmed, however, in contrast to earlier investigations at signi®cantly dierent compositions and with dierent shape of the homogeneity regions. This is particularly true for the phase regions of t 3-Al 3 NiTi 2 with the MgZn 2-type structure ranging from Al 30 Ni 28 Ti 42 (composition lowest in Al) to Al 50 Ni 16 Ti 34 (composition richest in Al) and for t 2-Al 2 NiTi. The complex atom site substitution mechanism in t 3 changing from Ti/Al exchange at Al-poor compositions towards Ni/Al replacement for the Al-rich part was monitored in detail by quantitative X-ray powder diraction techniques (Rietveld analyses). In contrast to earlier reports, claiming a two-phase region Ni{Al x Ti 1-x } 2 +t 3 , we observed two closely adjoining three-phase equilibria: a 2-AlTi 3 +Ni{Al x Ti 1-x } 2 + t 4-AlNi 2 Ti and a 2-AlTi 3 +t 3-Al 2 NiTi 2 +t 4-AlNi 2 Ti. The earlier reported ``homogeneous phase at Al 23 Ni 26 Ti 51 H '' was shown by high resolution microprobe and X-ray diraction measurements to be an extremely ®negrained eutectic. The experimental results are in ®ne agreement with the thermodynamic calculation.

Zeitschrift Fur Anorganische Und Allgemeine Chemie, 2010

The constitution of the ternary system Ni/Si/Ti is investigated over the entire composition range using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), differential thermal analysis (DTA), and metallography. The solid state phase equilibria are determined for 900 °C. Eight ternary phases are found to be stable. The crystal structures for the phases τ1NiSiTi, τ2Ni4Si7Ti4, τ3Ni40Si31Ti13, τ4Ni17Si7Ti6, and τ5Ni3SiTi2 are corroborated. For the remaining phases the compositions are determined as Ni6Si41Ti53 (τ6), Ni16Si42Ti42(τ7), and Ni12Si45Ti43 (τ8). The reaction scheme linking the solid state equilibria with the liquidus surface is amended to account for these newly observed phases. The discrepancies between previous experimental conclusions and modeling results are addressed. The liquidus surface is dominated by the primary crystallisation field of τ1NiSiTi, the only congruently melting phase.

Journal of Alloys and Compounds, 2007

The isothermal section of the Nd-Fe-Sb ternary system at 773 K over the whole composition ranges have been studied mainly by means of X-ray powder diffraction (powder XRD), with the aid of differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive analysis. Two new ternary compounds NdFeSb 3 and ∼NdFe 2.5 Sb 2 were found. Three ternary compounds Nd 6 Fe 13 Sb, NdFe 1−x Sb 2 and NdFe 4 Sb 12 were confirmed.

Acta Materialia, 2003

Phase equilibria in the a/a 2 phase region of the Ti-Al-Si-Nb system at Nb content 2.5, 3.5 and 5 at.% were studied in alloys as-cast and heat-treated at 800°C. Samples were prepared by arc-melting technique, homogenized at 1350°C and then heat-treated at 800°C, followed by ice water cooling. The structure of the alloys was characterized by means of X-Ray diffraction, differential thermal analysis, electron probe microanalysis, scanning electron microscopy and transmission electron microscopy. The continuous solid solutions with variable compositions (Ti 1Ϫx ,Nb x) 3 (Si 1Ϫy ,Al y) (h) (0.05ՅxՅ0.07, 10 Ϫ3 ՅyՅ 0.02) was detected at 800°C for the first time in the multi-component alloys based upon the Ti-Si system. It was stabilized by Nb additions in the alloys with low Al content. A peritectoid reaction b + a→h was observed. Additions of Al neutralized the stabilizing effect of Nb resulting in an a + Ti 5 Si 3 (z) equilibrium.

Journal of Phase Equilibria and Diffusion, 2020

Phase equilibria in the Ni-Si-Zr ternary system have been investigated experimentally by means of x-ray diffraction and electron probe micro-analyzer on equilibrated ternary alloys. Four ternary phases were detected at 1023 and 1173 K. The Ni 16 Si 7 Zr 6 phase tends to present in two different contrasts and has a wide homogeneity range. The reported Ni 2 Si 9 Zr 14 phase is not detected in this work. It is proposed that the Ni 2 Si 9 Zr 14 phase is unstable at these temperatures. As for the binary phases, Ni 5 Zr and Ni 7 Zr 2 dissolve appreciable amounts of Si and cNi 31 Si 12 , bNi 3 Si, dNi 2 Si, NiSi 2 exhibit a considerable solubility of Zr.

Journal of Phase Equilibria and Diffusion, 2014

The nature of liquid-solid phase equilibria in the Al-rich corner of the Al-Si-Ti system are determined by drawing three isothermal sections at 620, 680 and 727°C. The solubility of Ti in Al-Si liquids is determined for four different compositions (0, 9, 13 and 18 at.%Si) at temperature below 800°C. Combination of the two sets of experimental results leads to an attempt of liquidus projection. The primary crystallization surface of Al 3 Ti is found to extend up to 9.5 at.%Si in the liquid phase at 620°C and 11 at.%Si at 727°C. The solubility of Ti is found to be not significantly dependent on the Si content of the liquid. From DSC measurements and deduction on microstructure, the last invariant reaction of the solidification path is found to be quasi-peritectic: L þ s

The phase equilibria between S(bcc), a(hcp), Ti,Al-ar(hcp) and TigSi,(hcp) in the Ti-Al-Si system have been investigated in the temperature range of 700 to 1200°C. Isothermal sections of the ternary phase diagram have been assessed employing thermodynamic software, which uses the compound-energy model to describe mathematically the phase. Available experimental phase equilibria results on the Ti-Al-Si system were used to calculate missing binary and ternary interaction parameters and assess isothermal phase diagrams. Extrapolations in the resulting tie-triangles indicate the existence of three eutectoid reactions in the Ti-rich comer of the ternary diagram: B->a+Ti& a->ar+Ti,Si, and E-zar+Ti,Si,. Additionally, extrapolations in the pta,+a tie-triangle observed at 1100°C indicate that two possibilities arise to represent a peritectoid reaction involving a, E and a2 phases: p+a,->a and P+a-x2, depending on the alloy composition and on the effect of temperature on the solubility of Si in a phase. 0

Calphad, 2009

The isothermal cross-section of the phase diagram of the system Er-Al-Si at 873 K was constructed based on X-ray powder diffraction. The existence of the compounds Er 2 Al 3 Si 2 (Y 2 Al 3 Si 2-type structure), ErAlSi (YAlGe), Er 2 AlSi 2 (W 2 CoB 2), and Er 2 Al 1.5 Si 1.5 (Mo 2 FeB 2) were confirmed and the formation of three new ternary alumosilicides was established: ErAl 2.8 Si 0.2 (HT-PuAl 3 , hP24, P6 3 /mmc, a = 0.60295(4), c = 1.42308(9) nm), ∼Er 5 Al 6 Si 4 (unknown structure), and Er 6 Al 3 Si (Tb 6 Al 3 Si, tI80, I4/mcm, a = 1.1436(2), c = 1.4854(2) nm).

Materials Research Bulletin, 1999

The ternary phase diagram AlâOâ-SiOâ-LaâOâ was investigated at 1,300 C. The samples were prepared by wet chemical route (sol-gel synthesis) and characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), and EDX microprobe analysis. The XRD powder pattern data of LaââSiâOââ compound, as obtained by us, reconfirm the structure proposed in the literature, though with significantly different lattice parameters. No

Journal of The European Ceramic Society, 1995

where Ln = Nd and Sm have been determined. Forty-four compatibility tetrahedra were established in the region Ln,O~Si,N,O,. Within this region, LnAlO,Si,_ ,AIX03,,N,_,) are the only two important compounds which have tie lines joined to /3-sialon and AINpolytypoid phases. aSiaIon coexists with the kP phase.

Intermetallics, 2001

Phase equilibria of Nb-Hf-Si at 1500 C have been investigated for the metal-rich end of the ternary phase diagram using scanning electron microscopy, electron probe microanalysis, and electron backscatter diffraction analysis. An isothermal section at 1500 C was constructed for this ternary system based on experimental data from 11 alloys heat treated at 1500 C for 100 h. Phase equilibria between the following silicides, Nb(Hf) 5 Si 3 , Hf(Nb) 5 Si 3 , Nb(Hf) 3 Si, Hf(Nb) 2 Si, Hf(Nb) 3 Si 2 , Hf(Nb) 5 Si 4 , Hf(Nb)Si, Nb(Hf)Si 2 , and two metal-rich solid solutions, b(Nb,Hf,Si) and a(Hf,Nb,Si) are described.

Journal of Phase Equilibria and Diffusion, 2004

An experimental investigation of the phase relations in the titanium (Ti)-aluminum (Al)-silicon (Si) system was undertaken by differential thermal analysis, x-ray diffraction, metallography, and microprobe analysis. The present measurements when combined with those from an earlier investigation at this laboratory provide data for 56 alloy compositions in the Ti-Al-Si system. The combined results allowed the construction of a solidus projection, a melting diagram including both solidus and liquidus, partial isothermal sections at 1270°C and 1250°C, three isopleths with a constant percentage of one or another component, and a reaction scheme.

Materials, 2022

In this work, two isothermal sections of the Co-Ta-Si ternary system at 900 • C and 1100 • C are constructed in the whole composition range via phase equilibrium determination with the help of electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. Firstly, several reported ternary phases G (Co 16 Ta 6 Si 7 ), G (Co 4 TaSi 3 ), E (CoTaSi), L (Co 3 Ta 2 Si) and V (Co 4 Ta 4 Si 7 ) are all re-confirmed again. The G phase is found to be a kind of high-temperature compound, which is unstable at less than 1100 • C. Additionally, the L phase with a large composition range (Co 32-62 Ta 26-36 Si 10-30 ) crystallizes with a hexagonal crystal structure (space group: P6 3 /mmc, C14), which is the same as that of the binary high-temperature λ 1 -Co 2 Ta phase. It can be reasonably speculated that the ternary L phase results from the stabilization toward low-temperature of the binary λ 1 -Co 2 Ta through adding Si. Secondly, the binary CoTa 2 and SiTa 2 phases are found to form a continuous solid solution phase (Co, Si)Ta 2 with a body-centered tetragonal structure. Thirdly, the elemental Si shows a large solid solubility for Co-Ta binary compounds while the Ta and Co are hardly dissolved in Co-Si and Ta-Si binary phases, respectively.