Isothermal Section of the Ti-Ta-Sn Ternary System at 1173 K

The phase equilibrium of the Ti-Ta-Sn ternary system at 1173 K was investigated experimentally using x-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The isothermal section on the whole composition range was constructed, where eight single-phase regions and seven three-phase regions coexisted. The ternary compound Ti₃₆Ta₂₈Sn₃₆ was found in the experiment, and two three-phase regions β-Ti₆Sn₅ + Ti₃₆Ta₂₈Sn₃₆ + Ta₃Sn and Ti₂Sn + Ti₃Sn + β(Ti, Ta) were experimentally detected. Experimental analysis shows that the solid solution β(Ti, Ta) dissolves up to approximately 21.2 at.% Sn, and that the maximum solubility of Ta in Ti₃Sn and Ti₅Sn₃ can reach up to 9.3 and 5.9 at.%, respectively. The solubility values of Ta in Ti₂Sn and β-Ti₆Sn₅ are no less than 7.3 and 15.5 at.%, respectively, whereas that of Ti in Ta₃Sn is no less than 8.8 at.%. The liquid phase mainly exists in the Sn-rich corner.     

Experimental Investigation of the Mo–Ti–Zr Ternary Phase Diagrams

In this work, the phase diagrams of the Mo–Ti–Zr ternary system were determined by means of X-ray diffraction, optical microscopy, and electron probe microanalysis. Two isothermal sections of the Mo–Ti–Zr ternary system at 900 and 1100 °C were experimentally established. There are three two-phase regions and one three-phase region at both isothermal sections. The existence of the three-phase region (β₁?+?Laves?+?β₂) at 900 and 1100 °C indicates that the β phase (bcc solid solution) separates into two phases, i.e. Mo, Ti rich solid solution β₁ and Ti, Zr rich solid solution β₂. No ternary compounds were detected. The maximum solubilities of Ti in the Laves phase were found to be 19.3 at.% at 900 °C and 18.3 at.% at 1100 °C, respectively. The liquidus projection and reaction scheme of the Mo–Ti–Zr system were also presented based on the present experimental work and literature information.     

Sintering Behavior and Microstructure Formation of Titanium Aluminide Alloys Processed by Metal Injection Molding

The sintering behavior of metal injection molded titanium aluminide alloys, their microstructure formation and resulting mechanical properties were investigated. As reference material, the alloy Ti-45Al-5Nb-0.2B-0.2C at.% (TNB-V5) was selected. Additionally, two other variations with Mo and Mo + Si additions were prepared: Ti-45Al-3Nb-1Mo-0.2B-0.2C at.% and Ti-45Al-3Nb-1Mo-1Si-0.2B-0.2C at.%. The results indicate that the optimum sintering temperature was slightly above the solidus line. With proper sintering parameters, very low porosities (<0.5%) and fine microstructures with a colony size <85 µm could be achieved. Considering the sintering temperatures applied, the phase transformations upon cooling could be described as L + β → β → α + β → α → α + γ → α₂ + γ, which was in agreement with the microstructures observed. The effects of Mo and Si were opposite regarding the sintering behavior. Mo addition led to an increase in the optimum sintering temperature, whereas Si caused a significant decrease.     

Phase Equilibrium of the Fe-Cr-Ni-Al Quaternary System at 900 °C

The 900 °C isothermal sections of the Fe-Cr-Ni-Al quaternary with Fe fixed at 70 at.% and that with Ni fixed at 60 at.% have been determined by scanning electron microcopy coupled with energy dispersive spectroscopy and x-ray diffraction. Only one three-phase region marked as α-Fe + β-(Fe,Ni)Al + γ-Fe has been found in the 70Fe-Cr-Ni-Al section. With regard to the Fe-Cr-60Ni-Al section, there are three three-phase regions, i.e., α-Cr + γ-Ni + γ′-Ni₃Al, γ-Ni + γ′-Ni₃Al + β-(Fe,Ni)Al and α-Cr + β-(Fe,Ni)Al + γ′-Ni₃Al and one four-phase region, namely α-Cr + β-(Fe,Ni)Al + γ-Ni + γ′-Ni₃Al. No quaternary compound is found in the present work.     

Effect of Aging Treatment on the Formation of α Precipitates in β-Type Ti–6Mo–6V–5Cr–3Sn–2.5Zr Alloys

The microstructural evolution of a novel β-type Ti–6Mo–6V–5Cr–3Sn–2.5Zr (wt%) alloy subjected to different aging treatments was investigated. The normalized intensity of the α precipitates reached a peak value at 450 °C. A nanoscale orthorhombic phase was observed to coexist with α precipitates in the β matrix, which followed the Burgers orientation relation of 〈\(1120\)〉_α//〈111〉_β and {0001}_α//{110}_β. Fine α precipitates were formed with metastable O and β′ phases, and the β phase was spinodally decomposed to β and β′ phases. The maximum hardness value of the specimen was obtained after aging at 450 °C. Compositional partitioning of Mo, V, and Cr elements occurred with the depletion of fine acicular α precipitates upon aging 450 °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.     

Experimental Investigation of the Ti–V Side in the Ti–V–Sn Ternary System

Phase relations in the Ti–V–Sn system are of great importance for design of aerospace titanium alloys. However, reported Ti–V–Sn ternary phase diagrams present great differences. The isothermal section of the Ti–V side in the Ti–V–Sn system at 1073, 1173, and 1273 K was established using equilibria alloys. There are 11 two-phase equilibria and 3 three-phase equilibria, 9 two-phase equilibria and 3 three-phase equilibria, and 9 two-phase equilibria and 3 three-phase equilibria in the isothermal section at 1073, 1173, and 1273 K, respectively. In addition, remarkable ternary solubility in some binary compounds was detected, e.g., up to 21.18 and 22.23 at.% V in Ti₃Sn and Ti₂Sn, respectively, at 1273 K.     

Experimental Investigation of the Isothermal Section of the Fe-Mn-Sn System at 723 K

Phase relationships in the Fe-Mn-Sn ternary system at 723 K were investigated using equilibrated approach. More than 40 alloys were prepared by arc-melting method and examined by x-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopic. The existence of five binary compounds FeSn, FeSn₂, MnSn₂, Mn₃Sn₂, Mn₃Sn and one intermediate solid solution γ(Fe, Mn) have been confirmed in this system. FeSn₂ and MnSn₂ form continuous solid solution (Fe_1?x, Mn _x )Sn₂ (0 ≤ X ≤ 1) and the lattice parameters of (Fe, Mn)Sn₂ reduced linearly with increasing of Fe content. At 723 K, the maximum solid solubilities of Fe in αMn, βMn, Mn₃Sn, Mn₃Sn₂ phases and Mn in FeSn, αFe are about 25, 34.8, 37.3, 46.2 at.% Fe and 26.8, 5.5 at.% Mn respectively. The solid solubilities of γ(Fe, Mn) ranged from 42.1 to 78.1 at.% Fe and the limited solubility of Sn is around 3 at.%. The isothermal section consists of 6 three-phase regions, 13 two-phase regions and 9 single-phase regions. No ternary compound was found at 723 K in this system.     

The 600 °C Isothermal Section of the Al-Ni-Zn Ternary System

The 600 °C isothermal section of the Al-Ni-Zn ternary system was constructed based on wave dispersive x-ray spectrometry and x-ray power diffraction analysis. Eight three-phase regions have been identified in the Al-Ni-Zn ternary system at 600 °C. No new ternary compound was found in the system. The Liq. phase (η-Zn) can be in state of equilibrium with the Al₃Ni, Al₃Ni₂ and AlNi phases. The solubility of Ni in the Liq. phase is low, no more than 0.8 at.%. Binary phases AlNi and NiZn extend into the ternary system, and they co-exist in the Al-Ni-Zn ternary system at 600 °C. The three-phase triangles of (NiZn + AlNi + Ni₃Zn₁₄) and (AlNi3 + AlNi + NiZn) are constructed in this ternary system. As shown in this research result, the three-phase equilibrium relationship of the phases AlNi, Al₃Ni₅ and AlNi₃ has been confirmed in the present study.     

Phase equilibria in the Ni-rich portion of the Ni–Ga binary system

The phase equilibria in the composition range from 0 to 60 at% Ga of the Ni–Ga system were determined by electron probe microanalysis (EPMA) using diffusion couples, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). It was found that while the phase equilibria between the α′ (L1₂: Ni₃Ga) and α (Ni-solid solution) or β (B2: NiGa) phases are basically in agreement with the diagram evaluated by Lee and Nash, those between γ (B8₁: Ni₁₃Ga₇), δ (Cmmm: Ni₅Ga₃) and ɛ (C2/m: Ni₁₃Ga₉) are topologically different from that diagram. Three eutectoid reactions (γ → δ + ɛ, β → γ + ɛ, β → α′ + γ) and one peritectoid reaction (α′ + γ → δ) were confirmed and the temperatures and concentrations of those invariant reactions were determined.     

Phase Equilibria of the Co-Mo-Zr Ternary System at 1100 °C

The isothermal section of the Co-Mo-Zr ternary system at 1100 °C was constructed experimentally. A series of phases including their crystal structures and compositions were obtained by examining the annealed specimens through x-ray diffraction (XRD), optical microscopy (OM), and electron probe microanalysis (EPMA). It was confirmed that two ternary phases, λ₁ (Co_0.5-1.5Mo_1.5-0.5Zr, hP12-MgZn₂) and ? (CoMo₄Zr₉, hP28-Hf₉Mo₄B), exist in the Co-Mo-Zr ternary system at 1100 °C. And the experimental results also indicated that there are fourteen three-phase regions at 1100 °C. Ten of them were well determined in the present work: (1) (γCo) + Co₁₁Zr₂ + Co₂₃Zr₆, (2) (γCo) + Co₂₃Zr₆ + θ-Co₉Mo₂, (3) Co₂₃Zr₆ + θ-Co₉Mo₂ + 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 + CoZr + liquid and (10) ? + Mo₂Zr + (βZr). The maximum solubilities of Zr in μ-Co₇Mo₆ phase, Mo in Co₂Zr phase and Co in Mo₂Zr phase were determined to be 5.89, 12.57 and 9.95 at.%, respectively. While the solubilities of Zr in θ-Co₉Mo₂ and (γCo) phases, Mo in Co₁₁Zr₂ and CoZr phases were detected to be extremely small. According to this work, the Co₂₃Zr₆ phase contained 21.61 at.% Mo and 8.32 at.% Zr. In addition, the maximum solubilities of Co and Zr in (Mo) phase and Mo in (γCo) phase were measured to be 3.61, 5.60 and 11.20 at.%, respectively.     

Quasi-ternary System Cu2Te-CdTe-In2Te3

Phase equilibria in the quasi-ternary system Cu₂Te-CdTe-In₂Te₃ were investigated by differential thermal and x-ray phase analyses methods. Five vertical sections CuInTe₂-CdTe, ‘Cu_1.5In_0.5Te_1.5’-CdTe, CuInTe₂-CdIn₂Te_4, CuIn₅Te₈-CdTe, CuIn₅Te₈-CdIn₂Te₄ were constructed. System triangulation was performed, and the boundaries of six single-phase fields at 670 K were determined, which are the solid solution ranges of the components and the intermediate phases of the system. Liquidus surface projection was investigated, and we have identified a monovariant eutectic process L ? β + δ, and three nonvariant processes L_U + η ? δ + ε, β + δ ? α + ζ, δ ? γ + ε + η at 965 K, 847 and 690 K, respectively, that take place in the system.     

Phase transformation and microstructural features of NiAl/Ni<Subscript>3</Subscript>Al two-phase alloys containing ternary elements

Various ternary elements were added to observe the effects on the microstructural features of β+γ′ two-phase alloys. The microstructural features of β+γ′ two-phase (Ni₆₆Al₃₄)_100-χX_χ(X=Ti, Si, Nb) depended on the A_s (austenite start) temperature of β-martensite with alloying elements. For A_s>250°C, a lamellar microstructure was found to form by the following phase transformation: Martensite→Ni₅Al₃→β+γ’. For A_s<250°C, two-type microstructures, mesh and Widmanstätten, were formed depending on the ternary element. When Ti or Nb was added as a ternary element, the β→Ni₅Al₃ transformation occurred very quickly. Conversely, this transformation proceeded very slowly in the case of Si addition, and the resultant microstructure assumed somewhat different features. Consequently, it could be suggested that the microstructures of NiAl/Ni₃Al two-phase alloys are determined by not only the A_s temperature but also by the β→Ni₅Al₃ transformation.     

Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

A series of AlTiCr _x FeCoNiCu (x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr_0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr_1.5FeCoNiCu, AlTiCr_2.0FeCoNiCu, and AlTiCr_2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr _x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.     

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 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.     

Miscibility gap of B2 phase in NiAl to Cu3Al section of the Cu–Al–Ni system

The phase separation in the bcc phase of the Cu–Al–Ni system at 600–700 °C was investigated mainly by energy dispersion X-ray spectrometry (EDS) and differential scanning calorimetry (DSC). The compositions of the β₁ (A2 or B2: Cu-rich), β₂ (B2: NiAl-rich) and γ (γ-brass type) phases in equilibrium were determined. It was found that there is a β₁+β₂ miscibility gap in the β phase region as previously reported by Alexander. It was confirmed by means of high temperature in situ TEM observation that this miscibility gap consists of the B2+B2 phases but not the A2+B2 phases which is sometimes observed in many other Ni–Al and Co–Al base ternary bcc alloys. Thermodynamic calculation was performed which indicates that this characteristic feature suggests that the β₁ (B2)+β₂ (B2) miscibility gap is a part of a Cu-rich B2+NiAl-rich B2 miscibility gap island formed around the center of the composition triangle of the isothermal section. The phase separation in the β phase region and the stability of the ordered bcc aluminide are presented and discussed.     

Phase Equilibria in the Quaternary Ni-Re-Nb-Cr System at 1375 K Determined Using the Graph Method

Phase equilibria in the quaternary Ni-Re-Nb-Cr system at 1375 K have been determined by using the graph method combined with equilibrated alloys that were characterized with electron probe microanalysis and x-ray diffraction techniques. Three 4-phase equilibria, α + β_Cr + λ + σ, α + β_Nb + λ + χ, and α + γ + σ + Re, and three nonprojected 3-phase equilibria, α + λ + χ, α + λ + σ and α + σ + χ, have been experimentally established. In addition, the graph method suggested the existence of the following four other 4-phase equilibria in this system at 1375 K, α + β_Cr + γ + σ, α + β_Nb + λ + μ, α + λ + σ + χ, and α + σ + χ + Re.     

Microsegregation in high Nb containing TiAl alloy ingots beyond laboratory scale

Microsegregation in big ingots of Ti–45Al–(8–9)Nb–(W, B, Y) alloy had been studied. The composition and microstructural morphology of the large ingot exhibited significant microinhomogeneity. Three types of microsegregation were observed in as-cast microstructure of the large ingot. First is the solidification segregation (S-segregation) at interdendritic area, in which the composition is characterized by higher Al, B (boride), and Y (oxide) contents and lower Nb and W contents. Second is the β-segregation at the boundary and triple junctions among α grain due to the phase transformation of β → α. The composition at the segregation area is characterized by higher Nb and W additions that lead to the formation of β particles and γ phase. Third is the α-segregation that forms local lamellar structure composed of β, γ and α plates due to phase transformation of α → α₂ + β + γ. The microsegregation for the PAM ingot is lower than that for SM ingot in terms of the volume fraction of β phase. The reason is that the PAM melting can offer better control of pouring temperature and rather fast cooling rate by water-cooled copper crucible.     

Effects of cooling rate and initial composition on the solidification path and microstructure of Al-Cu-Si alloys

The influences of cooling rate and initial composition on solidification path, microstructure and hardness of Al-Cu-Si alloys were investigated. The results indicate that the solidification paths of alloys Al-3.7Cu-6.5Si, Al-5.2Cu-2.6Si and Al-15.1Cu-6.2Si were (L + α-Al)→(L + α-Al+ β-Si)→(L + α-Al+ β-Si+ θ-Al₂Cu), and the solidification paths of alloys Al-4.6Cu-0.9Si, Al-24.2Cu-3.9Si and Al-26.9Cu-2.1Si were (L + α-Al)→(L + α-Al+ θ-Al₂Cu)→(L + α-Al+ β-Si+ θ-Al₂Cu). Furthermore, it is found that the further the initial compositions from the binary eutectic trough and the slower the cooling rate was, the second dendrite arm spacing was larger and the volume percent of phase θ-Al₂Cu was fewer, and then influence the hardness. There were three kinds of (α-Al+ θ-Al₂Cu) binary eutectic, two kinds of (α-Al+ β-Si+ θ-Al₂Cu) ternary eutectic and one kind of (α-Al+ β-Si) binary eutectic morphologies existed in the solidification specimens.