Crystallographic Texture and Volume Fraction of <Emphasis Type="Italic">α</Emphasis> and <Emphasis Type="Italic">β</Emphasis> Phases in Zr-2.5Nb Pressure Tube Material During Heating and Cooling

The phase transformations in an as-received Zr-2.5Nb pressure tube material were characterized in detail by neutron diffraction. The texture and volume fraction of α and β phases were measured on heating at eight different temperatures 373 K to 1323 K (100 °C to 1050 °C) traversing across the α/(α + β) and (α + β)/β solvus lines, and also upon cooling at 1173 K and 823 K (900 °C and 550 °C). The results indicate that the α-phase texture is quite stable, with little change in the {0002} and { 11[`2]0 } \left\{ {11\bar{2}0} \right\} pole figures during heating to 1123 K (850 °C). The β-phase volume fraction increased while a slight change in texture was observed until heating reached 973 K (700 °C). On further heating to 1173 K (900 °C), there appears a previously unobserved α-phase texture component due to coarsening of the prior primary α grains; meanwhile the transformed β-phase texture evolved markedly. At 1323 K (1050 °C), the α phase disappeared with only 100 pct β phase remaining but with a different texture than that observed at lower temperatures. On cooling from the full β-phase regime, a different cooldown transformed α-phase texture was observed, with no resemblance of the original texture observed at 373 K (100 °C). The transformed α-phase texture shows that the {0002} plane normals are within the radial-longitudinal plane of the pressure tube following the Burgers orientation relationship of (110)<sub>bcc</sub>//(0002)<sub>hcp</sub> and [[`1]11]_\textbcc //[11[`2]0]_\texthcp [\bar{1}11]_{\text{bcc}} //[11\bar{2}0]_{\text{hcp}} with a memory of the precursor texture of the primary α grains observed on heating at 1173 K (900 °C).     

Phase Stability and Transformations in the Zr<Subscript>2</Subscript>Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> Amorphous System

Since Ni and Cu differ by only one valence electron, yet have nearly identical atomic sizes (1.27 vs 1.28 Å for Cu and Ni, respectively), the amorphous Zr₂Ni _x Cu_1?x system is ideal for isolating the effects of electronic structure on short- and medium-range order and the concomitant influence of both the structure and order on devitrification pathways. Thermal analysis, time-resolved high-energy X-ray diffraction (HEXRD), and transmission electron microscopy (TEM) were used to follow metastable and stable crystalline phase formation during devitrification. Using HEXRD, we observed that the first devitrification product in the Zr₂Ni system is the C16 structure, if oxygen is kept sufficiently low, while the Zr₂Cu system forms the C11b structure. For x = 0.25, the initial devitrification involves forming coexisting C11b and C16 phases. When Ni is increased to x ≥ 0.50, the initial devitrification only involves the C16 structure. These results are in complete accord with electronic structure calculations showing that the enthalpy of formation for the C11b phase is favored for x = 0, while enthalpies for C11b and C16 are nearly identical for x = 0.25; the C16 phase has the most negative enthalpy for all compositions in which x > 0.25.     

Tensile properties and creep behavior of a new Ti-Al-Nb intermetallic alloy with an O+<Emphasis Type="Italic">α</Emphasis><Subscript>2</Subscript> microstructure

A new Ti-Al-Nb alloy with a composition of Ti-27.5Al-13Nb (at. pct) was proposed. The density of this alloy was 4.7 g/cm³, which is about 13 pct lower than that for O+B2 alloys. After hot processing, the alloy was heat treated under two conditions: directly aged at 850 °C (DA treatment), or cooled from above the β-transus temperature with a cooling rate of 3 °C/min and then aged at 850 °C (BCA treatment). Under the present heat-treatment conditions, the phase constitution was primarily O+α ₂. A very fine Widmanstätten microstructure was obtained after the DA treatment, while a microstructure with coarse O plates was obtained after the BCA treatment. The tensile properties were investigated at 20 °C to 950 °C, and the creep behavior was investigated at 650 °C to 750 °C/90 to 380 MPa. The elongation to fracture at room temperature for the DA-treated tensile specimen was as high as 2.6 pct, despite the high Al content in this alloy. In comparison with the O+B2 ternary alloys, this alloy showed higher specific proof stress at temperatures over 800 °C and higher creep strength. The stress exponent and the apparent activation energy for creep were calculated. The fracture mechanism was discussed.     

Magnetic states in Fe<Subscript>65</Subscript>(Ni<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>35</Subscript> alloys

The ferromagnetic-antiferromagnetic concentration transition in Fe₆₅(Ni_{1 − x} Mn _x )₃₅ alloys is studied by neutron diffraction and small-angle magnetic neutron scattering (SMNS). The Curie and Néel temperatures are measured, and the antiferromagnetic moments and the cross sections of SMNS by magnetic heterogeneities are determined. The parameters of spin density fluctuations in the heterogeneities are obtained. A cluster mechanism of the nucleation of magnetic phases is revealed, and the spin-glass freezing temperatures are estimated. A low-temperature diagram is constructed for the magnetic states of the alloys.     

Effects of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and CaO/SiO<Subscript>2</Subscript> Ratio on Phase Equilbria in the ZnO-“FeO”-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-SiO<Subscript>2</Subscript> System in Equilibrium with Metallic Iron

The phase equilibria and liquidus temperatures in the ZnO-“FeO”-Al₂O₃-CaO-SiO₂ system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-“FeO”-(Al₂O₃ + CaO + SiO₂) with fixed CaO/SiO₂ and (CaO + SiO₂)/Al₂O₃ ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al₂O₃ concentration as well as the CaO/SiO₂ ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.     

Synthesis and Electrochemical Properties of Lithium–Vanadium Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript>2</Subscript>O<Subscript>5</Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0.1–0.3) Bronzes

Lithium–vanadium Li _x V₂O₅ (x = 0.1–0.3) bronzes are synthesized by solid-phase and soft chemistry methods. Their electrical properties are studied. Cells with an Li _x V₂O₅ cathode and a solid or liquid lithium anode are subjected to electrochemical cycling. The lithium–vanadium bronzes synthesized by the soft chemistry method are shown to have higher electrochemical characteristics.     

Synthesis and structural characterization of nanocrystalline Ni<Subscript>50</Subscript>Al<Subscript>50 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mo<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> intermetallic compound prepared by mechanical alloying

Nanocrystalline Ni₅₀Al_{50 ? x} Mo _x (x = 0, 0.5, 1, 2.5, and 5) intermetallic powders were synthesized by mechanical alloying (MA). Microstructural characterization and structural changes of powder particles during mechanical alloying were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirmed that the synthesis behavior of NiAl intermetallic depends on the Mo content and milling time. The SEM micrograph outcomes confirmed the specimen with longer milling time includes finer and more homogenous particles with attention to the ones with lesser milling time. Mo enhance has a considerable effect on the lowering of crystallite size. The TEM image showed that the Ni₅₀Al₄₅Mo₅ nano-particles were less than 10 nm.     

Thermomechanical and electrophysical properties of a solid electrolyte based on Na–β&quot;-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with <Emphasis Type="Italic">t</Emphasis>-ZrO<Subscript>2</Subscript> additions

The strength, the fracture toughness, the thermal shock resistance, and the electrical conductivity of a ceramic Na–β"-Al₂O₃ solid electrolyte modified by t-ZrO₂ additions are studied. The influence of the reverse t-ZrO₂ → m-ZrO₂ transformation on the mechanical and functional properties of the ceramics is discussed. The ZrO₂ addition concentration is found to affect the sodium-ion conductivity of the solid electrolyte and its activation energy. The degree of defect accumulation in the ceramics modified by 8.5 wt % t-ZrO₂ is shown to decrease during a thermal shock.     

The Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiB<Subscript>2</Subscript>/Fe Complex Reinforcement on Wear and Mechanical Properties of Al-Matrix Composites

In this study, the effect of Al₂O₃–TiB₂/Fe complex ceramic–metal reinforcement (CCMR) on wear and mechanical properties of Al-(Al₂O₃–TiB₂/Fe) composites were investigated. For this purpose, Al₂O₃–TiB₂/Fe CCMR was synthesized by mechanochemical process. The produced reinforcement powders were added to Al matrix, milled for 10 h and then hot extruded. The results showed that the metallic component (Fe rich phase) in this reinforcement acted as a pin, sticking the ceramic parts (Al₂O₃–TiB₂) to Al matrix. The best volume percentage of CCMR in Al matrix was recognized to be about 2.5 %. This composite showed a combination of wear resistance (0.005 mg/m), strength (500 MPa) and ductility (of about 6 %).     

Effects of the Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Content on the Viscosity of CaO-SiO<Subscript>2</Subscript>-10 Pct Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Quaternary Slag

The present study experimentally investigates the effect of Cr₂O₃ on the viscosity of molten slags. The viscosities of CaO-SiO₂-10 pct Al₂O₃-Cr₂O₃ quaternary slags with two different binary basicities (R, basic slag with R = 1.2 and acidic slag with R = 0.8) were measured by the rotating cylindrical method from 1813 K to 1953 K (1540 °C to 1680 °C). The results showed that the viscosity of both types of slag decreased as the Cr₂O₃ content increased, but the viscosity of acidic slags exhibited a greater decrease. The slags showed good Newtonian behavior at such high temperatures. Cr₂O₃ could act as a network modifier to simplify the Si-O-Si tetrahedral structure, as verified by the Raman spectral analysis, which was consistent with the decreasing trend of viscosity. The activation energy of viscous flow decreased slightly with increasing Cr₂O₃, but increasing the basicity seemed to be more effective in decreasing the viscosity than adding Cr₂O₃.     

The effect of the aging period on the martensitic transformation and kinetic characteristic of at % Cu<Subscript>68.09</Subscript>Al<Subscript>26.1</Subscript>Ni<Subscript>1.54</Subscript>Мn<Subscript>4.27</Subscript> shape memory alloy

In this work, the effect of aging period on the characteristic transformation temperatures, thermodynamic parameters and structural variations of CuAlNiMn shape memory alloys were investigated. Aging was performed at above the austenite finish temperature of the un-aged specimen (120°C) for six different retention times, namely 1h, 2h, 3h, 4h, 5h and 6h. The changes in the transformation temperatures were examined by differential scanning calorimetry at different heating/cooling rates. The aging period was found to have an effect on the characteristic austenite and martensite transformation temperatures and thermodynamic parameters such as the enthalpy and entropy of alloys. High-temperature order-disorder phase transitions were determined using a differential thermal analysis, which showed that all the un-aged and aged specimens had an A2 → B2, B2 → L2₁ and an L2₁ → 9R, 18R transition. The structural analysis of the un-aged and aged specimens was performed through X-ray diffraction measurements at room temperature. The intensities of the diffraction peaks varied according to the aging time.     

Solid Phase Equilibrium Relations in the CaO-SiO<Subscript>2</Subscript>-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-La<Subscript>2</Subscript>O<Subscript>3</Subscript> System at 1273 K

Silicate slag system with additions Nb and RE formed in the utilization of REE-Nb-Fe ore deposit resources in China has industrial uses as a metallurgical slag system. The lack of a phase diagram, theoretical, and thermodynamic information for the multi-component system restrict the comprehensive utilization process. In the current work, solid phase equilibrium relations in the CaO-SiO₂-Nb₂O₅-La₂O₃ quaternary system at 1273 K (1000 °C) were investigated experimentally by the high-temperature equilibrium experiment followed by X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer. Six spatial independent tetrahedron fields in the CaO-SiO₂-Nb₂O₅-La₂O₃ system phase diagram were determined by the Gibbs Phase Rule. The current work combines the mass fraction of equilibrium phase and corresponding geometric relation. A determinant method was deduced to calculate the mass fraction of equilibrium phase in quaternary system according to the Mass Conservation Law, the Gibbs Phase Rule, the Lever’s Rule, and the Cramer Law.     

Regularities of the contact interaction of double carbides (Ti<Subscript>1 –<Emphasis Type="Italic">n</Emphasis></Subscript>Me<Stack><Subscript><Emphasis Type="Italic">n</Emphasis></Subscript><Superscript>IV,V</Superscript></Stack>)C with the Ni–Mo melt

Regularities of dissolution, phase formation, and structure formation during the interaction of double carbides (Ti_1–n Me _n ^{IV, V} )C with the Ni–25%Mo melt (t = 1450°C, τ = 1 h, vacuum 10^–1 Pa) are investigated for the first time by electron probe microanalysis and scanning electron microscopy. The role of each alloying metal in the composition and microstructure formation of studied compositions is revealed. It is established that Group IV alloying metals (Zr and Hf) almost do not enter the composition of the forming K-phase (carbide Ti_1–n Mo _n C _x ); therefore, its composition is independent of their concentration in double carbide. In contrast with zirconium and hafnium, Group V alloying metals (V and Nb) actively participate in the formation of the K-phase; however, the dependences of the composition of the K-phase and metallic matrix on the vanadium and niobium content are the opposite in this case. An interpretation of the causes of these distinctions is proposed.     

Microstructure,Texture, and Mechanical Properties of <Emphasis Type="Italic">β</Emphasis> Solution-Treated and Aged Metastable <Emphasis Type="Italic">β</Emphasis> Titanium Alloy,Ti-5Al-5Mo-5V-3Cr

The current study describes the aging characteristics and mechanical properties of a metastable β titanium alloy Ti-5Al-5Mo-5V-3Cr. The aged microstructures consist of fine α-phase precipitates (lath morphology) in equiaxed β grains. The sizes of the α-phase precipitates increase with the increasing aging temperature. The β ST WQ and 823 K (550 °C)-aged material exhibits maximum hardness due to precipitation hardening. The low- and high-temperature aging conditions result in strong c-type basal and prismatic textures in the α-phase, respectively. The β-phase of the alloy aged at low temperature reveals the presence of texture with moderate intensity. In contrast, high-temperature-aged material exhibits very strong β-phase texture. The strengths of the alloy under β ST WQ- and 923 K (650 °C)-aged conditions are the maximum and minimum along TD and RD, while the ductility values are the maximum and minimum along the RD and TD direction samples, respectively. The flow curves follow typical Holloman equation along three sample directions, and the work hardening rate curves display two distinctive regimes, namely, stage I and stage II. The yield locus plots of the β ST WQ and aged materials exhibit the presence of anisotropy.     

Continuous cooling <Emphasis Type="Italic">β</Emphasis>-to-<Emphasis Type="Italic">α</Emphasis> transformation behaviors of extra-pure and commercially pure Ti

The in-situ continuous cooling β-to-α transformation kinetics of extra-pure (EP) Ti and of grade-4 commercially pure (CP) Ti were investigated using a fully computer-controlled resistivity-temperature realtime measurement apparatus and transmission electron microscopy. The β-to-α′ martensitic transformation occurs under near pure shear condition, and the habit plane of lath-type martensite was determined to be parallel to , which is in good agreement with the prediction of the crystallographic theory. The M _s temperature of EP-Ti was measured as 800 °C and can be raised by up to about 40 °C due to the generation of thermal stress and local deformation during rapid cooling. The massive transformation was, for the first time, observed to occur over a wide range of cooling rates in an EP-Ti. The massive start temperature and its occurrence were, unlike the martensitic transformation, hardly affected by the generation of thermal stress and local deformation during rapid cooling. The stable regime of massive transformation in a grade-4 CP-Ti was considerably shifted toward a slower cooling rate side and was significantly contracted at the same time. This is because the presence of iron impurity not only largely suppresses the massive transformation but also significantly delays a long-range diffusional transformation.