The Gd-Al-Si Isothermal Section at 500 °C

Phase relations in the Gd-Al-Si system have been established and experimentally studied at 500 °C. The system has been experimentally investigated by mean of scanning electron microscopy (SEM), electron microprobe analysis (EDXS) and x-ray powder diffraction (XRPD). The existence of four ternary compounds has been confirmed: τ₁ GdAl₂Si₂ (hP5-CaAl₂Si₂ type), τ₂ GdAlSi (tI12-αThSi₂ type), τ₃ Gd₄AlSi₃ (oC8-CrB type) and τ₄ Gd₆Al₃Si (tI80-Tb₆Al₃Si type). Three ternary compounds show a composition homogeneity range: τ₂ dissolves Si up to about 37 at.%, τ₃ shows an homogeneity range (towards the GdSi compound) to 45 at.% Si concentration value, finally the τ₄ phase dissolves 5 at.% of Si. All binary compounds dissolve the third element, except for GdAl The ternary system is characterized by 16 three-phase fields, and 16 two-phase fields.     

Isothermal Section of the Al-Mn-Dy System at 500 °C

Phase relationships in the Al-Mn-Dy ternary system at 500 °C have been investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and electron probe microanalysis. From the experimental results it was concluded that the isothermal section consists of 16 single-phase regions, 26 two-phase regions and 12 three-phase regions. Two extensive solid solutions, (Al _x Mn_1?x )₁₂Dy and (Al_1?x Mn _x )₂Dy, were observed. The solid solution (Al _x Mn_1?x )₁₂Dy forms by Al replacing Mn in Mn₁₂Dy, while the continuous solid solution (Al_1?x Mn _x )₂Dy forms by Mn and Al mutually substituting in Al₂Dy and Mn₂Dy, respectively. The maximum solid solubility of Al in Mn₁₂Dy is 79.3 at.%.     

Experimental Investigation of the Zn-Al-Sb System at 450 °C

An isothermal section of the Zn-Al-Sb ternary system at 450 °C has been established by equilibrating 11 samples of different compositions and phase identification by optical and scanning electron microscopy with energy dispersive spectroscopy, x-ray diffraction after quenching to room temperature. Five three-phase regions exist in the system at 450 °C. No ternary compound has been found. And, the compound AlSb with 2.1 at.% Zn can equilibrate with all phases in the system. Experimental results indicate that the solubility of Sb in α-Al phase is too limited to be detected. The SbZn, Sb₂Zn₃, and Sb₃Zn₄ phases, which have little Al solubility (at most 3.3 at.%), were observed in the system.     

The 450 °C Isothermal Section of the Zn-Fe-Ti System

The 450 °C isothermal section of the Zn-Fe-Ti ternary system with an emphasis on the Zn-rich corner was experimentally determined by means of optical microscopy, scanning electron microscopic/energy-dispersive spectrometric (SEM-EDS) analysis, and x-ray diffraction. A true ternary phase T with an approximate formula of TiFe₂Zn₂₂ has been identified. This phase is in equilibrium with all phases in the system, except and Ti₂Zn. Four Ti-Zn binary compounds, TiZn₁₆, TiZn₈, TiZn₃, and TiZn, were found in this study.     

High-Temperature Oxidation Behavior of SIMP Steel at 800 °C

In this work, the high-temperature oxidation behavior of SIMP and commercial T91 steels was investigated in air at 800 °C for up to 1008 h. The oxides formed on the two steels were characterized and analyzed by XRD, SEM and EPMA. The results showed that the weight gain and oxide thickness of SIMP steel were rather smaller than those of T91 steel, that flake-like Cr₂O₃ with Mn_1.5Cr_1.5O₄ spinel particles formed on SIMP steel, while double-layer structure consisting of an outer hematite Fe₂O₃ layer and an inner Fe–Cr spinel layer formed on T91 steel, and that the location of the oxide layer spallation was at the inner Fe–Cr spinel after 1008 h, which led the ratio between the outer layer and the inner layer to decrease. The reason that SIMP steel exhibited better high-temperature oxidation resistance than that of T91 steel was analyzed due to the higher Cr and Si contents that could form compact and continuous oxide layer on the steel.     

450 °C Isothermal Section of the Zn-Fe-Cu Ternary System

The 450 °C isothermal section of the Zn-Fe-Cu ternary system was experimentally determined by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectrometer (EDS)/Wave Dispersive X-ray Spectrometer (WDS), and X-ray Diffractometer (XRD). Eight three-phase regions exist in the 450 °C isothermal section of the Zn-Fe-Cu ternary system. No new ternary compound was found in the system. The δ_Fe phase (FeZn₁₀) can be in equilibrium with all phases except the α-Fe, (Cu) and β′ (CuZn) phase. Experimental results indicated that the solubility of Cu in the Γ (Fe₃Zn₁₀) and the δ_Fe phase reaches as high as 17.9 and 15.2 at.%, respectively.     

700 °C Isothermal Section of the Al-Ti-Si Ternary Phase Diagram

The 700 °C isothermal section of the Al-Ti-Si ternary phase diagram has been determined experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray powder diffraction. Fourteen three-phase regions have been determined experimentally in the isothermal section at 700 °C. The ternary phases τ₁ (I4₁/amd, Zr₃Al₄Si₅-type) and τ₂ (Cmcm, ZrSi₂-type) are confirmed in the system at 700 °C. The compositions of τ₁ and τ₂ are found as Al_6.2-9.3Ti_32.4-34.0Si_57.5-60.9 and Al_10.0-11.6Ti_34.2-34.5Si_53.9-55.6, respectively. The τ₃ and Ti₃Al₅ phases are not found in the section. The Ti-rich corner at 700 °C shows the presence of three three-phase equilibriums, i.e., (TiAl + Ti₃Al + Ti₅Si₃), (α-Ti + Ti₃Si + Ti₅Si₃) and (α-Ti + Ti₃Al + Ti₅Si₃). The maximum solubility of Al in Ti₅Si₃, Ti₃Si and α-Ti is 6.0, 1.5 and 13.9 at.% at 700 °C, respectively. The maximum solubility of Si in L-Al, TiAl₃, TiAl₂, TiAl, Ti₃Al and α-Ti is 24.1, 13.6, 1.5, 0.8, 2.3 and 2.3 at.%, respectively.     

Phase Equilibria of the Al-Sc-Zr Ternary System at 500 °C

Phase equilibria of the Al-Sc-Zr ternary system at 500 °C have been experimentally investigated by determining twenty-seven equilibrium alloys. X-ray diffraction and electron probe microanalysis were used to identify the phases and their compositions. The isothermal section of the Al-Sc-Zr system at 500 °C was constructed based on the experimental results and the information on the three constituent binary systems. Sixteen two-phase equilibrium regions and ten three-phase equilibrium regions were included and no ternary compounds were observed. The experimental results indicated that all the binary intermetallic compounds exhibited appreciable solubility of the third component. Besides, the continuous solid solution θ (Al(Sc, Zr)₂) forms between AlSc₂ and AlZr₂.     

Phase Equilibria of the Co-Mo-Zr Ternary System at 1000 °C

The isothermal section of the Co-Mo-Zr ternary system at 1000 °C was investigated by using 29 alloys. The annealed alloys were examined by means of x-ray diffraction, optical microscopy, and electron probe microanalysis. It was confirmed that three ternary phases, λ₁ (Co_0.5-1.5Mo_1.5-0.5Zr, hP12-MgZn₂), ω (CoMoZr₄) and κ (CoMo₄Zr₉, hP28-Hf₉Mo₄B), exist in the Co-Mo-Zr ternary system at 1000 °C. And the experimental results also indicated that there are sixteen three-phase regions at 1000 °C. Thirteen of them were well determined in the present work: (1) (γCo)?+?Co₁₁Zr₂?+?Co₂₃Zr₆, (2) (γCo)?+?Co₂₃Zr₆?+?ε-Co₃Mo, (3) Co₂₃Zr₆?+?ε-Co₃Mo?+?μ-Co₇Mo₆, (4) (Mo)?+?μ-Co₇Mo₆?+?Co₂Zr, (5) (Mo)?+?Co₂Zr?+?λ₁, (6) (Mo)?+?Mo₂Zr?+?λ₁, (7) λ₁?+?Mo₂Zr?+?CoZr, (8) Co₂Zr?+?CoZr?+?λ₁, (9) Mo₂Zr?+?CoZr₂?+?ω, (10) κ?+?Mo₂Zr?+?ω, (11) CoZr₂?+?liquid?+?ω, (12) (βZr)?+?liquid?+?ω and (13) (βZr)?+?κ?+?ω. The homogeneity of λ₁ spans in the range of 28.66-50.77 at.% Co and 15.71-37.03 at.% Mo, and that for ω is within the range of 18.66-23.64 at.% Co and 8.53-14.68 at.% Mo. The homogeneity range for κ is from 8.09 at.% to 9.94 at.% Co and 23.13 at.% to 25.58 at.% Mo. The maximum solubility of Zr in μ-Co₇Mo₆ phase, Mo in Co₂Zr phase and Co in Mo₂Zr phase were determined to be 6.17, 11.27 and 9.14 at.%, respectively. While the solubility of Zr in ε-Co₃Mo and (γCo) phases, Mo in Co₁₁Zr₂ and CoZr phases were detected to be extremely small. According to this work, the Co₂₃Zr₆ phase contained 15.61 at.% Mo and 12.7 at.% Zr. In addition, the maximum solubility of Co and Zr in (Mo) phase and Mo in (γCo) phase were measured to be 3.50, 5.44 and 7.40 at.%, respectively.     

Phase Equilibria of the Al-Zn-Fe-Ti Quaternary System at 600 °C

Isothermal sections of the Al-Zn-Fe-Ti quaternary system at 600 °C with Al being fixed at 75 and 50 at.%, respectively, have been determined experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray powder diffraction. Two four-phase regions and nine four-phase regions have been identified in the 75 at.% Al and 50 at.% Al sections, respectively. Two Al-Fe-Ti ternary phases τ₂ (Al₂FeTi; D8_a, Mn₂₃Th₆-type cubic), τ₃ (Al₈FeTi₃; L1₂, AuCu₃-type cubic) and one Zn-Fe-Ti ternary phase T have been found in 50 at.% Al section. The XRD analysis of Al₅₀Zn₂₅Ti₂₅ indicates it is not a true ternary compound but the extension of TiZn₃. The Ti₂Al₅ phase which exists at temperature above 1150 °C in Ti-Al binary system is also found in the two isothermal sections.     

450 °C Isothermal Section of the Fe-Al-Sb Ternary Phase Diagram

The 450 °C isothermal section of the Fe-Al-Sb ternary phase diagram has been determined experimentally using scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, and x-ray diffraction. No ternary compound is found in this system at 450 °C. Experimental results indicate that Sb cannot dissolve in the Fe-Al compounds, e.g. FeAl₂, Fe₂Al₅, and FeAl₃. While the maximum solubilities of Al in FeSb and FeSb₂ are 3.2 and 1.3 at.%, respectively, and 0.5 at.% Fe is detected in AlSb.     

Measurement of 900 °C Isothermal Section in the Mo-Ni-Zr System

The isothermal section of the Mo-Ni-Zr system at 900 °C was investigated by characterization of eighteen equilibrium alloys. Electron probe microanalysis (EPMA) and x-ray diffraction (XRD) were used to identify the phases and obtain their compositions. The existence of two ternary compounds, Zr₆₅Mo_18?x Ni_16.5+x (τ₁, cF96-Ti₂Ni) and Zr₆₅Mo_27.3Ni_7.7 (τ₂, hP28-Hf₉Mo₄B), was confirmed in the Zr-rich corner, and the compositions of the two phases were determined. The isothermal section of the Mo-Ni-Zr system at 900 °C consists of 15 three-phase regions and 29 two-phase regions. The following three-phase equilibria were well established: (1) (Ni) + Ni₇Zr₂ + Ni₅Zr, (2) MoNi + MoNi₃ + Ni₇Zr₂, (3) Ni₇Zr₂ + MoNi + (Mo), (4) (Mo) + Ni₇Zr₂ + Ni₃Zr, (5) (Mo) + Ni₃Zr + Ni₂₁Zr₈, (6) (Mo) + Ni₂₁Zr₈ + Ni₁₀Zr₇, (7) (Mo) + Ni₁₀Zr₇ + NiZr, (8) (Mo) + Mo₂Zr + NiZr, (9) NiZr₂ + Mo₂Zr + τ₁, (10) τ₁ + Mo₂Zr + τ₂, (11) τ₂ + Mo₂Zr + (Zr)ht, (12) NiZr₂ + τ₁ + (Zr)ht and (13) τ₁ + τ₂ + (Zr)ht. Several binary phases, such as MoNi₃, Ni₇Zr₂ and Mo₂Zr, dissolve appreciable amount of the third component.     

Phase Equilibria of the Zr-Si-Y Ternary System at 900 °C

The isothermal section of the Zr-Si-Y ternary system at 900 °C has been investigated using x-ray power diffraction, Scanning electron microscopy coupled with energy-/wave-dispersive x-ray spectroscopy. Nine three-phase equilibrium regions were determined experimentally. No ternary compound was observed in the present work. The 9 binary compounds Zr₂Si, Zr₃Si₂, Zr₅Si₄, ZrSi, ZrSi₂, Y₅Si₃, Y₅Si₄, YSi and Y₃Si₅ were confirmed to exist in the Zr-Si-Y ternary system at 900 °C. The solubility of the third component in the binary compound was determined experimentally.     

The 400 °C Isothermal Section of the La-Co-Mg Ternary System

The isothermal section of the La-Co-Mg system at 400 °C was determined by characterization of about thirty ternary alloys synthesised by induction melting in sealed Ta crucibles and then annealed. Scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDXS) and x-ray powder diffraction (XRPD) were used to analyze microstructures, identify phases, measure their compositions and determine their crystal structures. Phase equilibria are characterized by the absence of ternary solid solutions and by the presence of three ternary phases. The existence and the crystal structure of the La_4?x CoMg_1 + x (τ₁, 0 ≤ x ≤0.15, cF96-Gd₄RhIn) were confirmed and its homogeneity region determined; the new phases La_23?x Co₇Mg_4 + x (τ₂, ?0.50≤ x ≤0.60, hP68-Pr₂₃Ir₇Mg₄) and ~La₃₈Co₅₅Mg₇ (τ₃, unknown crystal structure) were detected.     

Diffusion in FCC Co-rich Co-Al-W Alloys at 900 and 1000 °C

Diffusion couple experiments between various Co-rich face centered cubic (FCC) alloys in the Co-W-Al ternary system have been conducted at 900 and 1000 °C. Diffusion coefficients have been extracted for the Co-W binary and for ternary alloys at compositions where the diffusion paths cross. In addition, a least squares method has been utilized to optimize diffusion mobility parameters using DICTRA simulations to best fit the experimental concentration versus distance curves. Predictions of the diffusion matrix using the refined mobility database are in good agreement with the values obtained at the diffusion path crossing points.     

Phase Equilibria of 450 °C Isothermal Section of Zn-Al-Mg-Si Quaternary System

The isothermal section of the Zn-Al-Mg-Si quaternary system at 450 °C with Zn fixed at 70 at.% has been determined by means of scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction. The results show that there exist the following equilibria regions in the isothermal section: Liq. + α-Al + MgZn₂ + Mg₂Si and Liq. + α-Al + Mg₂Si + (Si) four-phase regions, and Liq. + α-Al + Mg₂Si, Liq. + α-Al + MgZn₂, Liq. + MgZn₂ + Mg₂Si, Liq. + α-Al + (Si) and Liq. + MgZn₂ + (Si) three-phase regions. Si is almost insoluble in MgZn₂ and α-Al. The maximum solubility of Al and Zn in Mg₂Si is 1.8 and 6.1 at.%, respectively. The maximum solubility of Al and Si in MgZn₂ is 3.2 and 0.5 at.%, respectively. No ternary and quaternary compounds were found in this study.     

The Zn-Rich Corner of the Zn-Fe-Al-Sb Quaternary System at 450 °C

The 450 °C isothermal section of the Zn-Fe-Al-Sb quaternary system with Zn fixed at 93 at.% has been studied experimentally using x-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. The (L + AlSb) field is in equilibrium with other phase fields in the section, except those near the 93Zn7Fe corner. The solubility of Sb in ζ, δ, T, Fe₂Al₅, and FeAl₃ phases is very limited. The Zn-Fe-Al ternary phase T (Al₆Fe₈Zn₈₆) was found to be in equilibrium with L, δ, Fe₂Al₅, and AlSb phase. The maximum solubilities of Zn in AlSb, Fe₂Al₅, and FeAl₃ are 5.3, 12.3, and 6.2 at.% respectively. Zn can be dissolved in all compounds existing in the equilibrium alloys. Five four-phase regions and four three-phase regions have been confirmed experimentally.     

Steam Oxidation Behavior of Advanced Steels and Ni-Based Alloys at 800 °C

This publication studies the steam oxidation behavior of advanced steels (309S, 310S and HR3C) and Ni-based alloys (Haynes^® 230^®, alloy 263, alloy 617 and Haynes^® 282^®) exposed at 800 °C for 2000 h under 1 bar pressure, in a pure water steam system. The results revealed that all exposed materials showed relatively low weight gain, with no spallation of the oxide scale within the 2000 h of exposure. XRD analysis showed that Ni-based alloys developed an oxide scale consisting of four main phases: Cr₂O₃ (alloy 617, Haynes^® 282^®, alloy 263 and Haynes^® 230^®), MnCr₂O₄ (alloy 617, Haynes^® 282^® and Haynes^® 230^®), NiCr₂O₄ (alloy 617) and TiO₂ (alloy 263, Haynes^® 282^®). In contrast, advanced steels showed the development of Cr₂O₃, MnCr₂O₄, Mn₇SiO₁₂, FeMn(SiO₄) and SiO₂ phases. The steel with the highest Cr content showed the formation of Fe₃O₄ and the thickest oxide scale.     

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

The oxidation behavior of Co-based Tribaloy T-800 alloy has been studied isothermally in air at 800 and 1,000 °C, respectively. The results showed that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800 °C. The oxide scale at this temperature exhibited a multi-layered structure including an outer layer of Co oxide, a layer composed of complex oxide and spinel, a nonuniform Mo-rich oxide layer, an intermediate mixed oxides layer and an internal attacked layer with different protrusions into Laves phase. During 1,000 °C exposure, it followed linear kinetics. The oxidation rendered a relatively uniform external Cr-rich oxide layer coupled with a thin layer of spinel on the top surface and voids at local scale/alloy interface and intergranular region together with internal Si oxide at 1,000 °C.     

Phase Equilibria of the Ti-Al-Nb System at 1000, 1100 and 1150 °C

1000, 1100 and 1150 °C isothermal sections of the Ti-Al-Nb system were studied using x-ray diffraction, scanning electron microscopy and electron probe microanalysis. A small island-like region of single β₀ is present at 1000, but absent at 1100 and 1150 °C. γ₁ is not a stable phase at 1000 and 1150 °C. Three three-phase fields (α₂?+?β₀?+?σ, β₀?+?σ?+?γ and α₂?+?β₀?+?γ) are identified in the 1000 °C isothermal section (30-60 at.% Ti content). The 1100 °C isothermal section is firstly studied completely. It includes six three-phase and thirteen two-phase fields. Two three-phase fields β?+?α₂?+?γ and β?+?σ?+?γ are identified in the isothermal section (30-60 at.% Ti content) at 1150 °C. These data are helpful to the fabrication of the TiAl and Ti₂AlNb intermetallics.