The niobium (columbium)-palladium constitution diagram

The Nb-Pd system was investigated over the entire composition range by metallography and X-ray diffraction analysis. The solubility limits of terminal and intermediate phases and solidus temperatures were determined. α-Nb dissolves ∼36 at. pct Pd at. 1520°C and ∼20 at. pct Pd at 800°C; α-Pd dissolves ∼31 at. pct Nb at 1610°C and ∼18 at. pct Nb at temperatures below 1500°C. The presence of three intermediate phases NbPd₂ (MoPt₂-type), α-NbPd₃ (TiAl₃-type), and β-NbPd₃ (β-NbPd₃-type) was confirmed; NbPd₂ melts at 1610°C and one of the NbPd₃ phases transforms at the same temperature into α-Pd solid solution which melts at 1625°C. In addition, an approximately equiatomic high-temperature phase α-NbPd with a homogeneity range of ∼11 at. pct was found which melts at 1520 to 1565°C and probably is an extension of and isomorphous with the α-Pd solid solution. Five three-phase reactions are described, and crystal chemical relationships are discussed. D. P. PARKER formerly with MIT . R. C. MANUSZEWSKI formerly with the ADAHF Research Unit at NBS.     

The niobium (columbium)-platinum constitution diagram

The Nb-Pt system was investigated over the entire composition range by metallography and X-ray diffraction analysis. The solubility limits of terminal and intermediate phases and solidus temperatures were determined. α-Nb dissolves ≈12 at. pct Pt at 2040 °C and ≈5 at. pct Pt at 1150 °C; α-Pt dissolves ≈20 at. pct Nb at 2000 °C and ≈ 18 at. pct Nb at temperatures below 1700 °C. The presence of six intermediate phases, Nb₃Pt (Cr₃O, A15 or β-W type), σ(≈Nb₂Pt, β-U type), Nb_1−xPt_1+x (AuCd type), α′-Pt (undetermined structure), NbPt₂ (MoPt₂ type), α-NbPt₃ (TiCu₃ type), and β-NbPt₃ (β-NbPt₃ type) was confirmed. The phase NbPt₃ melts congruently at ≈2040 °C, and σ forms peritectically at ≈1800 °C. By analogy with related systems, the high-temperature phase α′-Pt is probably an extension of and isomorphous with α-Pt solid solution. Eight three-phase reactions are described, the mean atomic volumes are given, and crystal chemical relationships among the six homologous T₅-T₁₀ systems (T₅ = V, Nb, Ta; T₆ = Pd, Pt) are discussed.     

Texture evolution and mechanical anisotropy in dual-phase Ti<Subscript>3</Subscript>Al-based alloy loaded at 700 °C to 1000 °C

The super α ₂ Ti₃Al-based alloy with a fine grain size of ∼2.2 μm exhibits superplastic elongations over 1000 pct at 920 °C to 1000 °C, 600 pct at 900 °C, 330 pct at 850 °C, and 140 pct at 750 °C. Mechanical anisotropy is observed in this alloy, and relatively lower flow stresses and higher tensile elongations are obtained in the 45 deg specimen loaded at 25 °C to 960 °C. The texture characteristics appear to impose significant influence on the mechanical anisotropy at temperatures below 900 °C (under the dislocation creep condition), and the {111}〈2 〉 and {0001} basal textures evolve in the β and α ₂ phases after tensile straining. At loading temperatures higher than 900 °C (under the superplastic flow condition), the anisotropy effect is less pronounced and the grain orientation distribution becomes basically random in nature. Rationalizations for the mechanical anisotropy in terms of the Schmid factor calculations for the major and minor texture components in the β and α ₂ phases provide consistent explanations for the deformation behavior at lower temperatures as well as the initial straining stage at higher temperatures.     

The vanadium-platinum constitution diagram

The system V-Pt was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe studies. There are at least four equilibrium intermediate phases in this system and they are stable to progressively higher temperatures with increasing vanadium concentration. The phases which have been observed are: γ^′, cubic, Cu₃Au type; θ, tetragonal, TiAl₃ type; δ, orthorhombic, MoPt₂ type; ζ, orthorhombic, AuCd type; and β, cubic, Cr₃Si type (A15). The gg^′ phase is possibly metastable. A very stable ribbon-like growth of ζ phase in the fcc platinum terminal solid solution has been observed in alloys containing about 43 at. pct V. The platinum terminal solid solution forms a congruent melting maximum at about 1805°C. A eutectic reaction occurs at 1720° ± 10°C and a peritectic reaction is indicated at 1800° ± 10°C. Vanadium is soluble in the fcc platinum terminal solid solution up to about 57 at. pct at 1720°C. Platinum dissolves only to the extent of about 12 at. pct at 1800°C in bcc α-V.     

Phase relationships in the neodymium-magnesium alloy system

The Nd-Mg system was studied using differential thermal analysis (DTA), X-ray examination, metallography, and microprobe analysis. The following intermetallic compounds were found to exist and their crystal structures confirmed or determined: NdMg (cubic, cP2 CsCl type, melting point 800 °C), NdMg₂ (cubic, cF24 MgCu₂ type, peritectic formation ∼755 °C), NdMg₃ (cubic, cF16 BiF₃ type, melting point 780 °C), and Nd₅Mg₄₁ (tetragonal, tI92 Ce₅Mg₄₁ type, decomposes peritectically at 560 °C). The NdMg₂ phase undergoes a eutectoidal decomposition at 660 °C. Three eutectic equilibria were observed to occur at 42.5 at. pct Mg and 775 °C, 64.5 at. pct Mg and 750 °C, and 92.5 at. pct Mg and 545 °C, respectively. In the Nd-rich alloys, previously determined data^[15] concerning the Mg solubility in α-Nd (8.2 at. pct Mg, ≈550 °C) were accepted. The Mg solubility in β-Nd was evaluated as 34 at. pct Mg at 775 °C. The β-Nd phase was observed to decompose eutectoidally at 17 at. pct Mg and 545 °C. Moreover, in the Mgrich alloys, a metastable NdMg₁₂ phase (tetragonal, tI26 ThMn₁₂ type) was observed in samples quenched from the liquid. The general properties of the Nd-Mg phases are compared with those of the R-Mg compounds and briefly discussed.     

Microstructure and phase relations for Ti-Mo-Al alloys

The influence of aluminum additions to a Ti-7 at. pet Mo alloy on the phase equilibria was investigated. The microstructures of the alloys, Ti-7 pct Mo-7 pct Al and Ti-7 pct Mo-16 pct Al, were determined by light and electron microscopy. It was found that with increasing aluminum concentration the formation of the metastable w phase was suppressed. In the Ti-7 pct Mo-16 pct Al alloy the β phase decomposed upon quenching by precipitating coherent, ordered particles having a B2 type of crystal structure (β₂). At low temperatures the equilibrium phases for this alloy were β + α+ β ₂, whereas at high temperature (850° to 950°C) the Ti₃Al phase was in two-phase equilibrium with the β phase. The four-phase equilibrium which exists at a temperature of about 550°C involves the reaction β + Ti₃Al ⇌ α + β₂. G. LUETJERING, formerly Staff Member Materials Research Center, Allied Chemical Corp., Morristown, N. J.,     

Phase equilibria in the binary rare-earth alloys: The erbium-magnesium system

The Er-Mg system was examined using differential thermal analysis (DTA), X-ray examination, metallography, and microprobe analysis. Four intermediate phases are found to exist, and their crystal structures have been confirmed or determined as the following:β phase (≈Er₂Mg) (cubic, cI2-W type, peritectic formation 1255 °C); ErMg (cubic, cP2-CsCl type, peritectic formation 830 °C); ErMg₂ (hexagonal, hP12-MgZn₂ type, peritectic formation 670 °C); and Er₅Mg₂₄ (cubic, cI58-α-Mn type, peritectic formation 600 °C). Theβ phase undergoes a eutectoidal decomposition at 680 °C and 30.5 at. pct Mg. A eutectic reaction was observed to occur at 570 °C and 89.5 at. pct Mg. Comparisons of the general properties between the ErMg phases and with those of the other R-Mg compounds (R = rare earth) are briefly discussed. Properties and structures of the R-Mg, R-rich alloys are specially considered and compared with those of a few groups of rare-earth alloys. The alloying behavior of R-rich R-Me alloys (R = Ho, Er, Tm, Lu; Me = Mg, Cd, In, Tl) is systematically presented and/or predicted.     

Microstructure and mechanical properties of Ti-40 Wt Pct Ta (Ti-15 At. Pct Ta)

Of the β-isomorphous Ti-X alloy systems, Ti-Ta is one of the least studied. In the current work, the microstructure and mechanical properties of Ti-40 wt pct Ta (Ti-15 at. pct Ta) are investigated. Annealing at 810 °C produces a two-phase microstructure consisting of Ti-richa idiomorphs in a continuous Ta-rich β matrix; this suggests the β-transus temperature is higher than indicated by the most recently published phase diagram. Water quenching from 810 °C causes the β phase to partially transform to orthorhombic martensite (α), while furnace cooling yields secondarya The primary α formed isothermally remains unchanged in both cases. Subsequent aging causes transformation of the martensite to type 1a plus residual β, with a corresponding increase in strength and decrease in ductility. The maximum ductility (20 pct elongation) occurs in the water-quenched condition in which metastable β is retained. Analysis of the true stresstrue strain data suggests that transformation-induced plasticity may contribute to the enhanced ductility of the water-quenched material.     

The Al-Cu-Fe phase diagram: 0 to 25 At. pct Fe and 50

Isothermal sections of the Al-Cu-Fe equilibrium phase diagram at temperatures from 680 °C to 800 °C were determined in the region with 50 to 75 at. pct Al and 0 to 25 at. pct Fe using scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques. This re- gion includes the face-centered icosahedral phase (Ψ-Al₆Cu₂Fe) which has unprecedented struc- tural perfection and no apparent phason strain. The icosahedral phase has equilibrium phase fields with four distinct phases at 700 °C and 720 °C (β-Al(Fe, Cu), λ-Al₁₃Fe₄, ω-Al₇Cu₂Fe, and liquid) and three phases at 680 °C(β, ω, and λ) and 800 °C (β, λ, and liquid). The B2 ordered β phase has considerably greater solubility for Cu than previously reported, extending from AlFe to ∼Al₅₀Fe₅Cu₄₅. The equilibrium range of composition for the icosahedral phase at these temperatures was determined, and a liquidus projection is proposed.     

The titanium-rich end of the Ti-Cd phase diagram

Ti-Cd alloys containing up to 30 at. pct Cd have been prepared by diffusing cadmium from the vapor phase into pure titanium. Phase relations in these alloys have been explored by metallographic and X-ray techniques. Cadmium has quite a large solubility in theβ phase of titanium at 1000°C. Addition of cadmium decreases theα-β transformation temperature, forming a eutectoid at approximately 785°C. The solubility of cadmium inα titanium at the eutectoid temperature is approximately 6.5 at. pct, decreasing with decreasing temperature. The phase in equilibrium with saturatedα titanium is an intermetallic compound based on the composition Ti₂Cd.     

On the fracture and fatigue properties of Mo-Mo<Subscript>3</Subscript>Si-Mo<Subscript>5</Subscript>SiB<Subscript>2</Subscript> refractory intermetallic alloys at ambient to elevated temperatures (25 °C to 1300 °C)

The need for structural materials with high-temperature strength and oxidation resistance coupled with adequate lower-temperature toughness for potential use at temperatures above ∼1000 °C has remained a persistent challenge in materials science. In this work, one promising class of intermetallic alloys is examined, namely, boron-containing molybdenum silicides, with compositions in the range Mo (bal), 12 to 17 at. pct Si, 8.5 at. pct B, processed using both ingot (I/M) and powder (P/M) metallurgy methods. Specifically, the oxidation (“pesting”), fracture toughness, and fatigue-crack propagation resistance of four such alloys, which consisted of ∼21 to 38 vol. pct α-Mo phase in an intermetallic matrix of Mo₃Si and Mo₅SiB₂ (T₂), were characterized at temperatures between 25 °C and 1300 °C. The boron additions were found to confer improved “pest” resistance (at 400 °C to 900 °C) as compared to unmodified molybdenum silicides, such as Mo₅Si₃. Moreover, although the fracture and fatigue properties of the finer-scale P/M alloys were only marginally better than those of MoSi₂, for the I/M processed microstructures with coarse distributions of the α-Mo phase, fracture toughness properties were far superior, rising from values above 7 MPa √m at ambient temperatures to almost 12 MPa √m at 1300 °C. Similarly, the fatigue-crack propagation resistance was significantly better than that of MoSi₂, with fatigue threshold values roughly 70 pct of the toughness, i.e., rising from over 5 MPa √m at 25 °C to ∼8 MPa √m at 1300 °C. These results, in particular, that the toughness and cyclic crack-growth resistance actually increased with increasing temperature, are discussed in terms of the salient mechanisms of toughening in Mo-Si-B alloys and the specific role of microstructure.     

The ternary phase diagram,Fe-Ni-P

In order to provide the necessary phase equilibria data for understanding the development of the Widmanstatten pattern in iron meteorites, we have redetermined the Fe-Ni-P phase diagram from 0 to 100 pct Ni, 0 to 16.5 wt pct P, in the temperature range 1100° to 550°C. Long term heat treatments and 130 selected alloys were used. The electron microprobe was employed to measure the composition of the coexisting phases directly. We found that the fourphase reaction isotherm, where α+ liq ⇌ γ+ Ph, occurs at 1000° ± 5°C. Above this temperature the ternary fields α+ Ph + liq and α+ γ+ liq are stable and below 1000°C, the ternary fields ⇌+ γ + Ph and γ + Ph + liq are stable. Below 875°C a eutectic reaction, liq → γ + Ph, occurs at the Ni-P edge of the diagram. Altogether nineteen isotherms were determined in this study. The phase boundary compositions of the two-and three-phase fields are listed and are compared with the three binary diagrams. The α + γ + Ph field expands in area in each isotherm as the temperature decreases from 1000°C. Below 800°C the nickel content in all three phases increases with decreasing temperature. The phosphorus solubility in α and γ decreases from 2.7 and 1.4 wt pct at 1000°C to 0.25 and 0.08 wt pct at 550°C. The addition of phosphorus to binary Fe-Ni greatly affects the α/α + γ and γ/α + γ boundaries below 900°C. It stabilizes the α phase by increasing the solubility of nickel (α/α +γ boundary) and above 700°C, it decreases the stability field of the γ phase by decreasing the solubility of nickel(@#@ γ/α + γ boundary). However below 700°C, phosphorus reverses its role in γ and acts as a γ stabilizer, increasing the nickel solubility range. The addition of phosphorus to Fe-Ni caused significant changes in the nucleation and growth processes. Phosphorus contents of 0.1 wt pct or more allow the direct precipitation ofa from the parent γ phase by the reaction γ ⇌ α + γ. The growth rate of the α phase is substantially higher than that predicted from the binary diffusion coefficients. Formerly at Planetology Branch, Goddard Space Flight Center     

Stress-assisted transformation in Ti-60 wt pct Ta alloys

An investigation of the influence of processing variables on mechanical properties and phase development for a Ti-60 wt pct Ta (Ti-28.5 at. pct Ta) alloy was conducted. The alloy was hot-rolled, subjected to heat-treatment temperatures above the β (bcc) transus (1 hour at 700 °C, 800 °C, or 900 °C), and water quenched. All heat treatment produced a combination of metastable β (bcc) and metastable α″ (orthorhombic martensite), with the amount of retained β essentially independent of heat treatment, ranging from 20 to 33 vol pct. Deformation of as-rolled and heat-treated tension specimens showed an anomalous leveling of the stress-strain curve in the stress-strain curves at low strains. X-ray diffraction (both simple 2ϑ diffractometry and texture analysis) on both deformed and undeformed material determined that the leveling of the stress-strain curve was a result of the β→α″ martensitic transformation. The stress required to initiate the transformation increased with prequench temperature. This was determined to be due to the presence of athermal ω. Grain growth kinetics have been determined in the course of this work.     

Study of the sintering of a Ti-9 pct Fe system by mossbauer spectroscopy

The first stages in the sintering of Ti-9 pct Fe were studied with the aid of room temperature M?ssbauer spectroscopy and X-ray diffractometry. At a sintering temperature of 800°C most of the αFe disappeared after ten hours, at 1000°C-after less than 10 minutes. The first stages of the densification process are controlled by the disappearance of theαFe phase, which causes a decrease in density. Density increases again only after that phase has completely disappeared. Small quantities of TiFe intermetallic as an intermediate phase were observed to form, which subsequently converted toβTi. These small quantities of the intermetallic as well as theαFe phase were discernible only by M?ssbauer spectroscopy, not by X-ray diffractometry. A model is presented to describe the formation of transient intermediate phases characteristic of the sintering process. This research was supported by the United States-Israel Binational Science Foundation.     

A sintering study on the β-spodumene-based glass ceramics prepared from gel-derived precursor powders with LiF additive

Beta-spodumene (Li₂O·Al₂O₃·4SiO₂, LAS) powders were prepared by a sol-gel process using Si(OC₂H₅)₄, Al(OC₄H₉)₃, and LiNO₃ as precursors and LiF as a sintering aid agent. Dilatometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and electron diffraction (ED) were utilized to study the sintering, phase transformation, microstructure, and properties of the β-spodumene glass-ceramics prepared from the gel-derived precursor powders with and without LiF additives. For the LAS precursor powders containing no LiF, the only crystalline phase obtained was β-spodumene. For the pellets containing less than 4 wt pct LiF and sintered at 1050 °C for 5 hours the crystalline phases were β-spodumene and β-eucryptite (Li₂O·Al₂O₃·2SiO₂). When the LiF content was 5 wt pct and the sintering process was carried out at 1050 °C for 5 hours, the crystalline phases were β-spodumene, β-eucryptite (triclinic), and eucryptite (rhombohedral (hex.)) phases. With the LiF additive increased from 0.5 to 4 wt pct and sintering at 1050 °C for 5 hours, the open porosity of the sintered bodies decrease from 30 to 2.1 pct. The grains size is about to 4 to 5 μm when pellect LAS compact contains LiF 3 wt pct as sintered at 1050 °C for 5 hours. The grains size grew to 8 to 25 μm with a remarkable discontinuous grain growth for pellet LAS compact contain LiF 5 wt pct sintered at 1050 °C for 5 hours. Relative densities greater than 90 pct could be obtained for the LAS precursor powders with LiF > 2 wt pct when sintered at 1050 °C for 5 hours. The coefficient of thermal expansion of the sintered bodies decreased from 8.3 × 10⁻⁷ to 5.2 × 10⁻⁷/°C (25 °C to 900 °C) as the LiF addition increased from 0 to 5 wt pct.     

Structure,tensile deformation,and fracture of a Ti3Al-Nb alloy

The development of Ti₃Al-Nb alloys is an excellent example of the recent resurgence of interest in the use of intermetallics for high-temperature applications. We examine, in this contribution, the structure of a typical alloy Ti-24A1-11Nb and show it to consist primarily of the ordered α₂ phase (based on Ti₃Al, DO₁₉) and β_o, (based on Ti₂NbAl, B2) phases, with small amounts of a third phase, which is distorted slightly to an orthorhombic symmetry from the D0₁₉ (hexagonal) structure. Tensile properties have been examined on samples heat-treated to vary the size, shape, and volume fraction of α₂ phase and the deformation and fracture behavior of the ordered, two-phase mixture established. The tensile ductility is seen to maximize at intermediate volume fractions of the α₂ and β_o phases (∼30 pct) at values of 6 to 10 pct elongation to fracture, depending on the grain size of the β_o phase. A rationale incorporating the failure modes of the two phases—cleavage of α₂ and slipband decohesion of β_o—has been evolved to explain the trends in ductility with heat treatment.     

Determination of the Fe-Ni and Fe-Ni-P phase diagrams at low temperatures (700 to 300 °C)

The α + γ two-phase fields of the Fe-Ni and Fe-Ni (P saturated) phase diagrams have been determined in the composition range 0 to 60 wt pet Ni and in the temperature range 700 to 300 °C. The solubility of Ni in (FeNi)₃P was measured in the same temperature range. Homogeneous alloys were austenitized and quenched to form α₂, martensite, then heat treated to formα (ferrite) + γ (austenite). The compositions of the α and γ phases were determined with electron microprobe and scanning transmission electron microscope techniques. Retrograde solubility for the α/(α + γ) solvus line was demonstrated exper-imentally. P was shown to significantly decrease the size of the α + γ two-phase field. The maximum solubility of Ni in α is 6.1 ± 0.5 wt pct at 475 °C and 7.8± 0.5 wt pct at 450 °C in the Fe-Ni and Fe-Ni (P saturated) phase diagrams, respectively. The solubility of Ni in α is 4.2 ± 0.5 wt pct Ni and 4.9 ± 0.5 wt pct Ni at 300 °C in the Fe-Ni and Fe-Ni (P saturated) phase diagrams. Ternary Fe-Ni-P isothermal sections were constructed between 700 and 300 °C. Formerly Research Assistant in Department of Metallurgy & Materials Engineering, Lehigh University, Bethlehem, PA.     

Structure and properties of a β solution treated,quenched, and aged si-bearing near-α titanium alloy

The microstructure, tensile properties, and fractographic features of a near-α titanium alloy, IMI 829(Ti-6.1 wt pct Al-3.2 wt pct Zr-3.3 wt pct Sn-1 wt pct Nb-05 wt pct Mo-0.32 wt pct Si) have been studied after aging over a temperature range of 550°C to 950°C for 24 hours following solution treatment in the β phase field at 1050°C and water quenching. Transmission electron microscopy studies revealed that aging at 625°C and above produced discrete silicides at α′ interplatelet boundaries. However, aging at 900°C and above has also resulted in the precipitation of β phase along the lath boundaries of martensite. The silicides have been found to have a hexagonal structure withc=0.36 nm anda=0.70 nm (designated as S₂ by earlier workers). There is a significant improvement in yield and ultimate tensile strength after aging at 625°C, but there is less improvement at higher aging temperatures. The tensile ductility is found to be drastically reduced. While the fracture surface of the unaged specimen shows elongated dimples, the aged samples show a mixed mode of fracture, consisting of facets, featureless parallel bands, and extremely fine dimples.     

Evolution and coarsening of Al2O3 dispersoids at 500 °C to 600 °C in a mechanically alloyed Al-Ti-O based material

The formation and coarsening of Al₂O₃ dispersoids have been investigated at 500 °C, 550 °C, and 600 °C in a mechanically alloyed (MA) extrusion of composition Al-0.35wt pct Li-1wt pct Mg-0.25wt pct C-10vol pct TiO₂ for times up to 1500 hours. In the as-extruded condition, the dispersed phases included Al₃Ti, Al₄C₃, MgO, cubic TiO (C-TiO), monoclinic TiO (M-TiO), TiO₂, and a small amount of Al₂O₃. However, numerous Al₂O₃ dispersoids (various polymorphs: η, γ, α, and δ) with “block-shaped” morphology were formed after heat treatment due to reduction of C-TiO, M-TiO, and TiO₂. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) showed conclusively the transformation of these phases to additional Al₂O₃ and Al₃Ti. High resolution TEM showed that the α-Al₂O₃ dispersoids exhibited some lattice matching with the α-Al matrix. Coalescence of the block-shaped Al₂O₃ dispersoids occurred after heat treatment, and Al₄C₃ also became attached to them. The length and width of the block-shaped Al₂O₃ dispersoids increased by a factor of ∼1.55 between 340 and 1500 hours at 600 °C.     

The Gd-Yb and Lu-Yb phase systems

The Gd-Yb and Lu-Yb phase systems were established by thermal analysis, X-ray diffrac-tion, metallography, electron microprobe and chemical analyses. The solubility of Yb in α-Gd ranges from 6.5 at. pct at 500°C to 19.0 at. pct at 1161°C. The addition of Yb to Gd lowers theβ (bec) to α (hcp) transformation temperature to an inverse peritectic reaction at 20.0 at. pct Yb and 1161°C. The addition of Yb to Gd lowers the melting point of Gd to a monotectic horizontal at 1183°C which extends from 21.0 to 71.0 at. pct Yb. The monotec-tic composition is 49.0 at. pct Yb. The solid solubility of Gd in Yb ranges from 0.2 at. pct at 500°C to 2.3 at. pct at 819°C. The melting point of Yb is raised from 816°C to 819°C by the addition of Gd while the γ (bee) toβ (fee) transformation temperature of Yb is lowered from 796°C to 780°C by the addition of Gd. The solubility of Yb in solid Lu ranges from 6.0 at. pct at 800°C to 15 at. pct at 1530°C. The addition of Yb to Lu lowers the melting point of Lu to a monotectic horizontal at 1530°C which extends from 15 to 90 at. pct Yb. The monotectic composition is approximately 30 at. pct Yb. The solid solubility of Lu in Yb ranges from less than 0.1 at. pct at 500°C to 0.3 at. pct at 817°C. The addition of Lu raises the melting point of Yb to 817°C and also raises theβ (fee) to y (bec) transformation temperature to 798°C.