Experimental Investigation and Thermodynamic Calculations of the Bi-Ge-Sb Phase Diagram

A phase diagram of the Bi-Ge-Sb ternary system was investigated experimentally by differential thermal analysis (DTA), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray powder diffraction (XRD) methods and theoretically by the CALPHAD method. The liquidus projection; invariant equilibria; and three vertical sections, Sb-Bi_0.5Ge_0.5, Ge-Bi_0.5Sb_0.5, and Bi-Ge_0.5Sb_0.5, as well as isothermal sections at 773 K and 373 K (500 °C and 100 °C), were predicted using optimized thermodynamic parameters for constitutive binary systems from the literature. In addition, phase transition temperatures of the selected samples with compositions along calculated isopleths were experimentally determined using DTA. Predicted isothermal sections at 773 K and 373 K (500 °C and 100 °C) were compared with the results of the SEM-EDS and XRD analysis from this work. In both cases, good agreement between the extrapolated phase diagram and experimental results was obtained. Alloys from the three studied vertical sections were additionally analyzed using the Brinell hardness test.     

Phase Equilibria of the Cu-Ti-Er System at 773?K (500?°C) and Stability of the CuTi3 Phase

The phase relationships of the Cu-Ti-Er ternary phase diagram at 773?K (500?°C) were investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and differential thermal analysis (DTA). It is confirmed in this work that the binary compounds Cu₉Er₂ and Cu₇Er₂ exist in the Cu-Er binary system at 773?K (500?°C). The stability of the CuTi₃ phase is confirmed in the Cu-Ti system. After heat treatment at 1023?K (750?°C) for 90 hours, the phase CuTi₃ is observed in the microstructure of the alloy 25Cu75Ti. The temperature of the eutectoid transformation, namely, ??-Ti ? ??-Ti?+?CuTi₃, is determined to be 1078?K (805?°C) in this work. The 773?K (500?°C) isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. None of the phases in this system reveals a remarkable homogeneity range at 773?K (500?°C).     

The Influence of Precipitation of Alpha2 on Properties and Microstructure in TIMETAL 6-4

Samples of Hot Isostatically Pressed (HIPped) powder of TIMETAL 6-4 (Ti-6Al-4V, compositions in wt pct unless indicated), which was HIPped at 1203 K (930 °C), and of forged bar stock, which was slowly cooled from above the beta transus, were both subsequently held at 773 K (500 °C) for times up to 5 weeks and analyzed using scanning and transmission electron microscopy and atom probe analysis. It has been shown that in the samples aged for 5 weeks at 773 K (500 °C), there is a high density of alpha2 (α₂, an ordered phase based on the composition Ti₃Al) precipitates, which are typically 5 nm in size, and a significantly smaller density was present in the slowly cooled samples. The fatigue and tensile properties of samples aged for 5 weeks at 773 K (500 °C) have been compared with those of the HIPped powder and of the forged samples which were slowly cooled from just above the transus, and although no significant difference was found between the fatigue properties, the tensile strength of the aged samples was 5 pct higher than that of the as-HIPped and slowly cooled forged samples. The ductility of the forged samples did not decrease after aging at 773 K (500 °C) despite the strength increase. Transmission electron microscopy has been used to assess the nature of dislocations generated during tensile and fatigue deformation and it has been found that not just is planar slip observed, but dislocation pairs are not uncommon in samples aged at 773 K (500 °C) and some are seen in slowly cooled Ti6Al4V.     

Thermal Behavior and Phase Transformation of TiO2 Nanocrystallites Prepared by a Coprecipitation Route

TiO₂ freeze-dried precursor powders were synthesized using a coprecipitation route that includes titanium tetrachloride (TiCl₄) as initial material prepared at 348 K (75 °C) and pH 7. Differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) and high resolution TEM were utilized to characterize the thermal behavior and phase transformation of the TiO₂ freeze-dried precursor powders after calcination. The main compound of the TiO₂ freeze-dried precursor powders was TiO₂·H₂O based on a TG analysis conducted at a heating rate of 20 K (20 °C)/min. The anatase TiO₂ (a-TiO₂) first appeared at 473 K (200 °C), then from a-TiO₂ transformed to rutile TiO₂ (r-TiO₂) at 773 K (500 °C). The activation energy of a-TiO₂ formation from TiO₂ freeze-dried precursor powders was 242.4 ± 33.9 kJ/mol, whereas, the activation energy of phase transformation from a-TiO₂ to r-TiO₂ was 267.5 ± 19.1 kJ/mol. The crystallite size of a-TiO₂ grew from 3.5 to 23.2 nm when raising the calcination temperature from 473 K to 873 K (200 °C to 600 °C). In addition, the crystallite size of r-TiO₂ increased from 17.4 to 48.1 nm when calcination temperature increased from 773 K to 1073 K (500 °C to 800 °C).     

Response to Thermal Exposure of Ball-Milled Cu-Mg/B2O3 Powder Blends

The response to thermal exposure of ball-milled Cu-Mg/B₂O₃ powder blends was investigated in the current study to explore the potential of powder metallurgy route to produce Cu-B alloys. Cu-20Mg alloy powder was mixed with B₂O₃ and subsequently ball milled for 1 hour. Ball milling alone failed to establish a reaction between Cu-Mg compounds and B₂O₃. When the ball-milled powder blend was heated, however, B₂O₃ was reduced by CuMg₂ <773 K (500 °C). The Cu₂Mg intermetallic phase, which has survived until 773 K (500 °C), was involved in the reduction of the remaining B₂O₃ at still higher temperatures, while excess Mg reacted with B to produce MgB₂ and MgB₆ compounds. Cu-Mg alloy with predominantly the CuMg₂ phase must be utilized to take advantage of the capacity of the CuMg₂ (Cu-43 wt pct Mg) compound to reduce B₂O₃ at temperatures as low as 773 K (500 °C). Once the Cu-43Mg alloy powder is mixed with B₂O₃ and the powder blend thus obtained is ball milled and subsequently heated at 500 °C, B₂O₃ is readily reduced by CuMg₂ to yield Cu, B, and MgO. The latter can be easily removed from the powder blend by acid leaching.     

Stability of Ni3(Al,Ti) Gamma Prime Precipitates in a Nickel-Based Superalloy Inconel X-750 Under Heavy Ion Irradiation

Phase stability of Ni₃(Al, Ti) precipitates in Inconel X-750 under cascade damage was studied using heavy ion irradiation with transmission electron microscope (TEM) in situ observations. From 333 K to 673 K (60 °C to 400 °C), ordered Ni₃(Al, Ti) precipitates became completely disordered at low irradiation dose of 0.06 displacement per atom (dpa). At higher dose, a trend of precipitate dissolution occurring under disordered state was observed, which is due to the ballistic mixing effect by irradiation. However, at temperatures greater than 773 K (500 °C), the precipitates stayed ordered up to 5.4 dpa, supporting the view that irradiation-induced disordering/dissolution and thermal recovery reach a balance between 673 K and 773 K (400 °C and 500 °C). Effects of Ti/Al ratio and irradiation dose rate are also discussed.     

Characterization of Continuous and Discontinuous Precipitation Phases in Pd-Rich Precious Metal Alloys

Aberration-corrected scanning transmission electron microscopy (AC-STEM), X-ray diffraction (XRD), electron backscatter diffraction, and electron probe microanalysis were applied to characterize continuous and discontinuous phase formation in precious metal alloys used in electrical contacts. The Pd-rich Paliney^® (^®Paliney is tradename of Deringer-Ney Inc., Bloomfield, CT) alloys contain Pd, Ag, Cu, Au, Pt (and Zn or Ni). With aging at 755 K (482 °C), nanometer-scale chemistry modulation was observed indicating spinodal decomposition. An ordered body-centered tetragonal (bct) structure was also observed with AC-STEM after the 755 K (482 °C) aging treatment and another phase, tentatively identified as β-Cu₃Pd₄Zn, was found by microscopy and XRD after prolonged holds at higher temperatures. During slow cooling or isothermal holds at high temperature [755 K to 973 K (482 °C to 700 °C)], a two-phase lamellar structure develops along grain boundaries by discontinuous precipitation. XRD and AC-STEM showed that the lamellar structure was comprised of Ag-rich and Cu-rich fcc phases (α ₁ and α ₂). The phases are discussed in relation to a pseudo-ternary diagram based on Ag-Cu-Pd, which provides a simplified representation of the discontinuous phase compositions in the multi-component alloy system.     

Activity Measurements of Mg in the Ternary Cu-Mg-Si System Using Thermogravimetric Knudsen Effusion Method

The high vapor pressure of Mg in comparison with Cu and Si enables the use of thermogravimetric Knudsen effusion method (KEM) to determine the thermodynamic properties of binary Cu-Mg, Mg-Si, and ternary Cu-Mg-Si alloys. In the current study, the weight loss of solid Mg with time has been determined at different constant temperatures between 705 K and 788 K (432 °C and 515 °C) by using KEM, and from these diagrams, the sublimation rate of Mg was calculated. By introducing the sublimation rates into the equation derived from the kinetic gas theory, the enthalpy change of sublimation reaction of Mg at the experimental temperatures was calculated to be 147.5 ± 6.5 kJ mol^?1, which is close to the 143.8 ± 0.5 kJ mol^?1 calculated using the thermodynamic data available in the literature. Similar procedure was also applied to the binary Cu-Mg, Mg-Si, and ternary Cu-Mg-Si alloys where the activities of Mg with respect to the Mg wt pct with W _Cu:W _Si = 20:80 were calculated. The diversion points in the activity–composition diagrams gave the phase boundary compositions in the phase diagrams. The phase boundary compositions of Mg in the alloys determined using KEM were in good agreement with the known binary and the constructed ternary phase diagram using FactSage thermochemical software and databases.     

Cryogenic Mechanical Properties of Warm Multi-Pass Caliber-Rolled Fine-Grained Titanium Alloys: Ti-6Al-4V (Normal and ELI Grades) and VT14

The effect of microstructural refinement and the β phase fraction, V _β, on the mechanical properties at cryogenic temperatures (up to 20 K) of two commercially important aerospace titanium alloys: Ti-6Al-4V (normal as well as extra low interstitial grades) and VT14 was examined. Multi-pass caliber rolling in the temperature range of 973 K to 1223 K (700 °C to 950 °C) was employed to refine the microstructure, as V _β was found to increase nonlinearly with the rolling temperature. Detailed microstructural characterization of the alloys after caliber rolling was carried out using optical microscopy (OM), scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD), and transmission electron microscopy (TEM). Complete spheroidization of the primary α laths along with formation of bimodal microstructure occurred when the alloys are rolled at temperatures above 1123 K (850 °C). For rolling temperatures less than 1123 K (850 °C), complete fragmentation of the β phase with limited spheroidization of α laths was observed. The microstructural refinement due to caliber rolling was found to significantly enhance the strength with no penalty on ductility both at room and cryogenic temperatures. This was attributed to a complex interplay between microstructural refinement and reduced transformed β phase fraction. TEM suggests that the serrated stress–strain responses observed in the post-yield deformation regime of specimens tested at 20 K were due to the activation of \( \left\{ {10\bar{1}2} \right\} \) tensile twins.     

Joint solubility of samarium and dysprosium in solid magnesium

The phase compositions of solid Mg–Sm–Dy alloys corresponding to the magnesium-corner region of the phase diagram are studied by optical and scanning electron microscopy, electrical resistivity measurements, and electron microprobe analysis. The obtained results allowed us to determine the joint solubility of samarium and dysprosium in solid magnesium at 500, 400, and 300°C; it decreases with decreasing temperature. The magnesium solid solution is found to be in equilibrium only with the Mg₄₁Sm₅ and Mg₂₄Dy₅ compounds, which are in equilibrium with the magnesium solid solution in the binary Mg–Sm and Mg–Dy systems.     

Phase Transformation and Microstructure of Zn2Ti3O8 Nanocrystallite Powders Prepared Using the Hydrothermal Process

This paper examines the phase transformation and microstructure of Zn₂Ti₃O₈ nanocrystallite powders prepared using the hydrothermal process that includes TiCl₄ and Zn(NO₃)₂·6H₂O as the initial materials. Differential thermal analysis, X-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction, nanobeam electron diffraction, and high resolution TEM were utilized to characterize the transition behavior of zinc titanate precursor powders after calcination. Nanocrystalline Zn₂Ti₃O₈ powders with a size range of about 5.0 to 8.0 nm were obtained when the precursor powders were calcined at 773 K (500 °C) for 1 hour. When the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 1 hour, the cubic crystal of Zn₂Ti₃O₈ with a _o = 0.8399 ± 0.0003 nm still remained the predominant crystalline phase and the crystallite size increased to 20.0 nm. In addition, ZnTiO₃ phase first appeared because of the 13.8 pct of Zn₂Ti₃O₈ decomposition when the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 1 hour. When the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 9 hours, the Zn₂Ti₃O₈ crystallites grew continuously to 80.0 nm and enhanced the crystallinity. When the precursor powders were calcined at 1273 K (1000 °C) for 1 hour, Zn₂TiO₄ crystallites with a _o = 0.8461 ± 0.0002 nm were the predominant crystalline phase.     

Experimental Investigation of the Ce-Mg-Mn Isothermal Section at 723 K (450 °C) via Diffusion Couples Technique

The isothermal section of the Ce-Mg-Mn phase diagram at 723 K (450 °C) was established experimentally by means of diffusion couples and key alloys. The phase relationships in the complete composition range were determined based on six solid–solid diffusion couples and twelve annealed key alloys. No ternary compounds were found in the Ce-Mg-Mn system at 723 K (450 °C). X-ray diffraction and energy-dispersive X-ray spectroscopy spot analyses were used for phase identification. EDS line-scans, across the diffusion layers, were performed to determine the binary and ternary homogeneity ranges. Mn was observed in the diffusion couples and key alloys microstructures as either a solute element in the Ce-Mg compounds or as a pure element, because it has no tendency to form intermetallic compounds with either Ce or Mg. The fast at. interdiffusion of Ce and Mg produces several binary compounds (Ce _x Mg _y ) during the diffusion process. Thus, the diffusion layers formed in the ternary diffusion couples were similar to those in the Ce-Mg binary diffusion couples, except that the ternary diffusion couples contain layers of Ce-Mg compounds that dissolve certain amount of Mn. Also, the ternary diffusion couples showed layers containing islands of pure Mn distributed in most diffusion zones. As a result, the phase boundary lines were pointing toward Mn-rich corner, which supports the tendency of Mn to be in equilibrium with all the phases in the system.     

A Comprehensive Study of Diffusion Bonding of Mg AZ31 to Al 5754, Al 6061 and Al 7039 Alloys

In the present study, microstructural and mechanical properties of diffusion bonding of AZ31–Mg with Al 5754, Al 6061, and Al 7039 alloys were compared under same conditions. The vacuum diffusion processes were performed at a temperature of 440 °C, the pressure of 29 MPa, and a vacuum of 1?×?10^?4 torr for 60 min. The microstructural characterizations were investigated using optical microscopy and scanning electron microscopy equipped with EDS analysis and linear scanner. The XRD analysis was performed to study phase figures near the interface zone. The results revealed the formation of brittle intermetallic compounds like Al₁₂Mg₁₇, Al₃Mg₂, and their other combinations at bonding interfaces of all samples. Additionally, the hardness of Al alloys seemed to play a key role in increasing diffusion rate of magnesium atoms toward the aluminum atoms, with Al 6061 alloy having the highest diffusion rate. It consequently led to an increase in diffusion rate and thus formation of a strong diffusion bonding between magnesium and aluminum alloys. The highest strength was about 42 MPa for the diffusion bonding between Mg AZ31 and Al 6061. Further investigations on surfaces indicated that the brittle phases especially Al₃Mg₂ caused brittle fracturing.     

Age Hardening of the Al0.5CoCrNiTi0.5 High-Entropy Alloy

Al_0.5CoCrNiTi_0.5 high-entropy alloy was synthesized by vacuum arc melting in a copper mold. This alloy was aged at 773 K to 1473 K (500 °C to 1200 °C) for 24 hours to investigate the microstructure and hardness. The hardness of the as-cast alloy is HV743, and it exhibits a dendritic structure, in which dendrite is composed of body-centered cubic (bcc), face-centered cubic (fcc), and σ phases, and interdendrite is an eutectic structure consisting of bcc and order bcc phases. Apparent age hardening appears at 873 K to 1173 K (600 °C to 900 °C), and no age softening occurs even after 1473 K (1200 °C) aging. The age hardening of this alloy is attributed to the transformation of the bcc phase to σ phase. Detailed variations of hardness and the microstructure of aged alloys are reported in this article.     

Dry Sliding Wear Behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy

Dry sliding wear tests were performed for Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy against AISI 52100 steel under the loads of 50 to 250 N at 298 K to 873 K (25 °C to 600 °C). The wear behavior of the alloy varied with the change of test conditions. More or less tribo-oxides TiO₂ and Fe₂O₃ formed on worn surfaces under various conditions. At lower temperature [298 K to 473 K (25 °C to 200 °C)], less and scattered tribo-oxide layers did not show wear-reduced effect. As more number of and continuous tribo-oxide layers appeared at higher temperatures [773 K to 873 K (500 °C to 600 °C)], the wear rate would be substantially reduced. It can be suggested that Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy possessed excellent wear resistance at 773 K to 873 K (500 °C to 600 °C). The wear-reduced effect of tribo-oxides seemed to depend on the appearance of Fe₂O₃ and the amount of tribo-oxides.     

Texture Evolution of Abnormal Grains with Post-Deposition Annealing Temperature in Nanocrystalline Cu Thin Films

We have examined the evolution of abnormal grain growth texture with increasing post-deposition annealing temperature in nanocrystalline Cu films (20 nm thick) deposited on an amorphous SiN _x (20 nm)/Si substrate. Texture is analyzed by a TEM-based orientation and phase mapping technique based on precession electron diffraction. The as-deposited film, which has an initial grain size of ~12 nm in diameter, already shows a signature of abnormal grain growth, exhibiting a bimodal grain size distribution. Texture is analyzed by calculating area fractions of major components. The overall texture of the as-deposited film is identified to be ??110??, but ??100?? grains occupy the largest fraction in the abnormally grown grain areas, followed by ??111?? grains. After annealing at 398 K, 573 K, and 773 K (125 °C, 300 °C, and 500 °C), the overall texture turns to ??112??. After annealing at 398 K (125 °C), abnormally grown grains have a major ??112?? component. The situation is similar for the film annealed at 573 K (300 °C). After annealing at 773 K (500 °C), the abnormal grain growth texture evolved into major ??111??. The ??100?? component found in the abnormal grain growth texture for the as-deposited film is clearly explained by elastic strain energy minimization and the ??111?? component for the as-deposited film and the film annealed at 773 K (500 °C) is explained by surface energy minimization. The development of the ??112?? texture obtained after annealing at 398 K and 573 K (125 °C and 300 °C) is not explained by either elastic strain energy minimization or surface energy minimization. We suggest that it is clarified by assuming that the Cu film system is perfectly elastic?Cplastic, which is associated with the Taylor factors.     

High-Temperature Mechanical Behavior of Extruded Mg-Y-Zn Alloy Containing LPSO Phases

The high-temperature mechanical behavior of extruded Mg_97?3x Y_2x Zn _x (at. pct) alloys is evaluated from 473 K to 673 K (200 °C to 400 °C). The microstructure of the extruded alloys is characterized by Long Period Stacking Ordered structure (LPSO) elongated particles within the magnesium matrix. At low temperature and high strain rates, their creep behavior shows a high stress exponent (n = 11) and high activation energy. Alloys behave as a metal matrix composite where the magnesium matrix transfers part of its load to the LPSO phase. At high-temperature and/or low stresses, creep is controlled by nonbasal dislocation slip. At intermediate and high strain rates at 673 K (400 °C) and at intermediate strain rates between 623 K and 673 K (350 °C and 400 °C), the extruded alloys show superplastic deformation with elongations to failure higher than 200 pct. Cracking of coarse LPSO second-phase particles and their subsequent distribution in the magnesium matrix take place during superplastic deformation, preventing magnesium grain growth.     

Effect of alloying elements on the formation of rolling texture in Mg-Nd-Zr and Mg-Li alloys

The effect of alloying on the texture of Mg-Nd-Zr and Mg-Li alloy sheets is studied using pole and inverse pole figures. The basal texture intensity in rolling of Mg-Nd-Zr alloys is shown to be substantially decreased due to the precipitation of dispersed intermetallic Mg₁₂Nd phase particles. As a result, the workability characteristics during deep drawing can be increased. Lithium alloying causes the formation of a prismatic rolling texture, which is unusual for magnesium alloys, as a result of the phase transformation of the lithium-based bcc phase into the magnesium-based hexagonal close-packed phase that obeys the Burgers orientation relationships.     

Carbide Precipitation During Tempering of a Tool Steel Subjected to Deep Cryogenic Treatment

Using transmission electron microscopy, Mössbauer spectroscopy, and measurements of hardness, the carbide precipitation during tempering of steel X153CrMoV12 containing (mass pct) 1.55C, 11.90Cr, 0.70V, and 0.86Mo is studied after three treatments: quenching at RT and deep cryogenic treatment, DCT, at 77 K or 123 K (?196 °C or ?150 °C). In contrast to some previous studies, no fine carbide precipitation after long-time holding at cryogenic temperatures is detected. After quenching at room temperature, RT, the transient ε(ε′) carbide is precipitated between 373 K and 473 K (100 °C and 200 °C) and transformed to cementite starting from 573 K (300 °C). In case of DCT at 123 K (?150 °C), only fine cementite particles are detected after tempering at 373 K (200 °C) with their delayed coarsening at higher temperatures. Dissolution of cementite and precipitation of alloying element carbides proceed at 773 K (500 °C) after quenching at RT, although some undissolved cementite plates can also be observed. After DCT at 123 K (?150 °C), the transient ε(ε′) carbide is not precipitated during tempering, which is attributed to the intensive isothermal martensitic transformation accompanied by plastic deformation. In this case, cementite is the only carbide phase precipitated in the temperature range of 573 K to 773 K (300 °C to 500 °C). If DCT is carried out at 77 K (?196 °C), the ε(ε′) carbide is found after tempering at 373 K to 473 K (100 °C to 200 °C). Coarse cementite particles and the absence of alloying element carbides constitute a feature of steel subjected to DCT and tempering at 773 K (500 °C). As a result, a decreased secondary hardness is obtained in comparison with the steel quenched at RT. According to Mössbauer studies, the structure after DCT and tempering at 773 K (500 °C) is characterized by the decreased fraction of the retained austenite and clustering of alloying elements in the α solid solution. It is suggested that a competition between the strain-induced transformation of the retained austenite and carbide precipitation during the wear can control the life of steel tools.     

Correlation Between Experimental and Calculated Phase Fractions in Aged 20Cr32Ni1Nb Austenitic Stainless Steels Containing Nitrogen

A centrifugally cast 20Cr32Ni1Nb stainless steel manifold in service for 16 years at temperatures ranging from 1073 K to 1123 K (800 °C to 850 °C) has been characterized using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), auger electron spectroscopy (AES), and X-ray diffraction (XRD). Nb(C,N), M₂₃C₆, and the silicide G-phases (Ni₁₆Nb₆Si₇) were all identified in a conventional SEM, while the nitride Z-phase (CrNbN) was observed only in AES. M₂₃C₆, Z-phase and G-phase were characterized in XRD. Thermodynamic equilibrium calculations using ThermoCalc Version S, with the TCS Steel and Fe-alloys Database (TCFE6), and Thermotech Ni-based Superalloys Database (TTNI8) were validated by comparing experimental phase fraction results obtained from both EPMA and AES. A computational study looking at variations in the chemical composition of the alloy, and how they affect phase equilibria, was investigated. Increasing the nitrogen concentration is shown to decrease G-phase formation, where it is replaced by other intermetallic phases such as Z-phase and π-phase that do not experience liquation during pre-weld annealing treatments. Suppressing G-phase formation was ultimately determined to be a function of minimizing silicon content, and understabilizing the Nb/(C + 6/7N) ratio.