Phase Identification of Cu-In Alloys with 45 and 41.25 at.% In Compositions

In this work, the thermal stability of Cu-In alloys with 45.0 and 41.2 at.% In nominal compositions was investigated by differential scanning calorimetry (DSC), scanning electron microscopy, wavelength dispersive spectroscopy, and in-situ synchrotron x-ray powder diffraction (S-PXRD) over a temperature range from 25 up to 400 °C. The studied samples are mainly composed of a Cu₁₁In₉ phase together with minor amounts of the B phase (based on the NiAs-Ni₂In type structure) and, in one of the samples, with a minor amount of pure In. No evidence of the Cu₁₀In₇ (41.2 at.% In) phase was detected, not even in the sample with 41.2 at.% In nominal overall composition. The combined use of the S-PXRD and DSC techniques allowed us to identify two phase transitions involving the Cu₁₁In₉ phase, one of them corresponding to the $ \upeta^{\prime} \rightleftharpoons {\text{B}} + {\text{Cu}}_{11} {\text{In}}_{9} $ reaction at T = 290 °C and the other to the peritectic $ \upeta^{\prime} + {\text{L}} \rightleftharpoons {\text{Cu}}_{11} {\text{In}}_{9} $ reaction at T = 311 °C.     

Transformations of Carbides During Tempering of D3 Tool Steel

The studies were performed on D3 tool steel hardened after austenitizing at 1050 °C during 30 min and tempering at 200-700 °C. Based on the diffraction studies performed from the extraction replicas, using electron microscopy, it was found that after 120-min tempering in the consecutive temperatures, the following types of carbides occur: $$ 200\;^\circ {\text{C}} \to \upvarepsilon + \upchi + {\text{ Fe}}_{ 3} {\text{C}},\quad 3 50\;^\circ {\text{C}} \to \upvarepsilon + \upchi + {\text{ Fe}}_{ 3} {\text{C,}} $$ $$ 500\;^\circ {\text{C}} \to \upchi + {\text{ M}}_{ 3} {\text{C }} + {\text{ M}}_{ 7} {\text{C}}_{ 3} ,\quad 600\;^\circ {\text{C}} \to \upchi + {\text{ M}}_{ 3} {\text{C }} + {\text{ M}}_{ 7} {\text{C}}_{ 3} , $$ $$ 700\;^\circ {\text{C}} \to {\text{M}}_{ 3} {\text{C }} + {\text{ M}}_{ 7} {\text{C}}_{ 3} . $$ Apart from higher mentioned carbides, there are also big primary carbides and fine secondary M₇C₃ carbides occurring, which did not dissolve during austenitizing.     

Modeling the Correlation of Composition-Processing-Property for TC11 Titanium Alloy Based on Principal Component Analysis and Artificial Neural Network

In the present investigation, the correlation of composition-processing-property for TC11 titanium alloy was established using principal component analysis (PCA) and artificial neural network (ANN) based on the experimental datasets obtained from the forging experiments. During the PCA step, the feature vector is extracted by calculating the eigenvalue of correlation coefficient matrix for training dataset, and the dimension of input variables is reduced from 11 to 6 features. Thus, PCA offers an efficient method to characterize the data with a high degree of dimensionality reduction. During the ANN step, the principal components were chosen as the input parameters and the mechanical properties as the output parameters, including the ultimate tensile strength ( $ \upsigma_{\text{b}} $ ), yield strength ( $ \upsigma_{0.2} $ ), elongation ( $ \updelta $ ), and reduction of area (??). The training of ANN model was conducted using back-propagation learning algorithm. The results clearly present ideal agreement between the predicted value of PCA-ANN model and experimental value, indicating that the established model is a powerful tool to construct the correlation of composition-processing-property for TC11 titanium alloy. More importantly, the integrated method of PCA and ANN is also able to be utilized as the mechanical property prediction for the other alloys.     

Pressure dependencies of copper oxidation for low- and high-temperature parabolic laws

Studies of the oxidation kinetics of copper have been conducted in the thin-film range at temperatures of 383–398 K and in the oxygen pressure range of 0.278–21.27 kPa; whereas in the thick-film regime at 1123 K, studies have been conducted in the oxygen pressure range of 2.53–21.27 kPa. Furthermore, the effect of continuously impressed direct current with oxygen pressure variation in Wagner's parabolic range has been studied also in order to have a better understanding of the effective charge on the migrating species. In the low-temperature range, the rate constant, k_P ∝ \(P_{O_2 }^{1/4} \) , suggesting that the migration of neutral vacancies in the growing film predominates. At high temperature, 1123 K, in the Wagnerian regime, the observed approximate pressure dependencies of the parabolic rate constants are the following: $$\begin{gathered} {\text{k}}_{\text{p}} (normal oxidation) \propto \sim {\text{P}}_{{\text{O}}_{\text{2}} }^{{\text{1/7}}} \hfill \\ {\text{k}}_{\text{p}} (sample cathodic) \propto \sim {\text{P}}_{{\text{O}}_{\text{2}} }^{{\text{1/5}}} \hfill \\ \end{gathered} $$ and $${\text{k}}_{\text{p}} (sample anodic) \propto \sim {\text{P}}_{{\text{O}}_{\text{2}} }^{{\text{1/10}}} $$ .     

Sulfidation properties of an Fe-26.4Cr-8Al-6Mn alloy at 973 and 1073 K in H2S-H2 atmospheres,10^{ - 4} \leqslant {\text{P}}_{{\text{S}}_{\text{2}} } \leqslant 10^2 {\text{Pa}}

The sulfidation behavior of an Fe-26.4Cr-8Al-6Mn (at.%) alloy in H₂S-H₂ atmospheres, \(10^{ - 4} \leqslant {\text{P}}_{{\text{S}}_{\text{2}} } \leqslant 10^2 {\text{Pa}}\) .     

Relationship of Ca, B, and AlP in Al–12.6Si alloy

P modification has been widely used in Al-Si piston industry, but trace of Ca element has great influence on the P modification efficiency. In this work, it is found that primary Si can be heterogeneously nucleated by AlP in near eutectic Al-12.6Si alloy, but Ca element may destroy the P modification efficiency, whereas the addition of B can recover the P modification efficiency in near eutectic Al-12.6Si alloy with high Ca containing. The microstructure transformation was related to the reaction of Ca, B, and AlP. According to the thermodynamic calculation, Ca may react with AlP and form Ca3P2 compound in Al-Si alloy, whereas, when B was added into the melt, AlP could be reformed. The reaction of Ca, B, and AlP can be shown as follows: 2AlP +3Ca→Ca3P2+2Al; Ca3P2+18B+2Al→3CaB6+2AlP. In addition, with B added into the Al-12.6Si alloy with Ca and P addition, the mechanical properties were improved compared with single Ca and/or P addition.     

Influence of Hydrogen and Water Vapour on the Kinetics of Chromium Oxide Growth at High Temperature

In support of the selection of structural materials for heat exchangers in helium-cooled high temperature reactors, the oxidation behaviour of the Ni-base chromia-former alloy 230 was investigated at 850 °C in diluted helium atmosphere with a low water vapour content. In such a media, the equivalent partial pressure of oxygen (imposed by the $ P_{{{\text{H}}_{2} {\text{O}}}} $ / $ P_{{{\text{H}}_{2}}} $ ratio) is very low ( $ P_{{{\text{O}}_{ 2} }}^{\text{eq}} $ around 10^?16 Pa). The equivalent partial pressure of oxygen has no straight influence on the parabolic rate constant (k _p); on the other hand, $ P_{{{\text{H}}_{2} }} $ and $ P_{{{\text{H}}_{2} {\text{O}}}} $ demonstrate a complex influence on k _p. Photoelectrochemistry analyses revealed that this oxide could simultaneously contain two types of cationic defects. Specific oxidation tests with D₂O showed that the oxide scale also contains hydrogen. A mechanist model is proposed in order to describe the scale growth using both cationic defects. Those theoretical results show, at least qualitatively, how $ P_{{{\text{H}}_{2} }} $ and $ P_{{{\text{H}}_{2} {\text{O}}}} $ may concurrently influence the oxidation rate.     

On the Liquid/Solid Phase Equilibria in the Al-Rich Corner of the Al-Si-Ti Ternary System

The nature of liquid-solid phase equilibria in the Al-rich corner of the Al-Si-Ti system are determined by drawing three isothermal sections at 620, 680 and 727 °C. The solubility of Ti in Al-Si liquids is determined for four different compositions (0, 9, 13 and 18 at.%Si) at temperature below 800 °C. Combination of the two sets of experimental results leads to an attempt of liquidus projection. The primary crystallization surface of Al₃Ti is found to extend up to 9.5 at.%Si in the liquid phase at 620 °C and 11 at.%Si at 727 °C. The solubility of Ti is found to be not significantly dependent on the Si content of the liquid. From DSC measurements and deduction on microstructure, the last invariant reaction of the solidification path is found to be quasi-peritectic: ${\text{L}} + \uptau_{1} - {\text{Ti}}_{7} {\text{Al}}_{5} {\text{Si}}_{12} \Leftrightarrow {\text{Al}} + {\text{Si}} .$      

Comparative TEM investigation on the precipitation behaviors in Cu–15wt%Sn alloy

The decomposition and precipitation behaviors of a quenched Cu–15wt%Sn alloy as a function of aging temperature were investigated using transmission electron microscopy (TEM). Focused ion beam (FIB) was employed to assist TEM specimen preparation. At 300 °C, the decomposition of the supersaturated α′ phase occurred at grain boundaries, displaying a cellular morphology. The lamellae were found with ζ and α phases, rather than with the equilibrium ε and α phases. The ζ and α phases exhibit a well-defined orientation relationship (OR) as $ (1\bar{1}0)_{\alpha } //(0001)_{\zeta } ,\;[11\bar{2}]_{\alpha } //[\bar{1}2\bar{1}0]_{\zeta } $ . On the other hand, at 320 °C, only incipient lamellar structures of several micron meters were observed, which were composed of the δ and α phases. At the same time, abundant intragranular precipitation of the ε phase in the form of platelets was observed, and OR as $ (1\bar{1}1)_{\alpha } //(001)_{\varepsilon } , $ [110] _α //[100] _ε exists between ε phase and the α phase. These contrasting precipitation behaviors are discussed from the viewpoint of crystallographic coherency of these phases.     

Creep Properties and Deformation Mechanisms of a FGH95 Ni-based Superalloy

By means of full heat treatment, microstructure observation, lattice parameters determination, and the measurement of creep curves, an investigation has been conducted into the microstructure and creep mechanisms of FGH95 Ni-based superalloy. Results show that after the alloy is hot isostatically pressed, coarse γ′ phase discontinuously distributes along the previous particle boundaries. After solution treatment at high temperature and aging, the grain size has no obvious change, and the amount of coarse γ′ phase decreases, and a high volume fraction of fine γ′ phase dispersedly precipitates in the γ matrix. Moreover, the granular carbides are found to be precipitated along grain boundaries, which can hinder the grain boundaries’ sliding and enhance the creep resistance of the alloy. By x-ray diffraction analysis, it is indicated that the lattice misfit between the γ and γ′ phases decreases in the alloy after full heat treatment. In the ranges of experimental temperatures and applied stresses, the creep activation energy of the alloy is measured to be 630.4 kJ/mol. During creep, the deformation mechanisms of the alloy are that dislocations slip in the γ matrix or shear into the γ′ phase. Thereinto, the creep dislocations move over the γ′ phase by the Orowan mechanism, and the $ \left\langle { 1 10 } \right\rangle $ 〈 1 10 〉 super-dislocation shearing into the γ′ phase can be decomposed to form the configuration of (1/3) $ \left\langle { 1 12 } \right\rangle $ 〈 1 12 〉 super-Shockleys’ partials and the stacking fault.     

The role of a preceding chemical reaction and reactive clusters in phase transitions of intermetallic compounds

By means of chemical and X-ray phase analysis with the use of a rotating disc electrode, it is found that the dissolution of Mg-Cu and In-Bi intermetallic compounds proceeds via magnesium ionization and subsequent $Mg_2 Cu\xrightarrow[{ - Mg^{2 + } }]{}MgCu_2 $ and $In_2 Bi\xrightarrow[{ - In^{3 + } }]{}InBi$ InBi phase regrouping. It is postulated that the process is accompanied by the formation of a defective crystal lattice and the appearance of reactive clusters, which interact to produce, at first, nuclei of a new phase and, then, the crystal lattice of a new intermetallic compound that is enriched in the electrochemically less active component.     

Diffusion Research in BCC Ti-Al-Ni Ternary Alloys

Interdiffusion in BCC phase of Ti-Al-Ni ternary system was investigated at 1473 K (1200 °C) by employing the diffusion-couple technique. The raw composition profiles resulting from interdiffusion treatment and retrieved from EMPA were first analytically represented by error function expansion (ERFEX), and the ternary interdiffusion and impurity diffusion coefficients were then extracted by the Whittle-Green and generalized Hall methods, respectively. The obtained main interdiffusion coefficients \( \tilde{D}_{\text{AlAl}}^{\text{Ti}} \) and two cross coefficients, i.e. \( \tilde{D}_{\text{AlNi}}^{\text{Ti}} \) and \( \tilde{D}_{\text{NiAl}}^{\text{Ti}} \), were found to increase with increasing composition of diffusing species, whereas the values of \( \tilde{D}_{\text{NiNi}}^{\text{Ti}} \) show no noticeable compositional dependence. The impurity diffusivities \( \tilde{D}_{{{\text{Al}}\left( {\text{Ti - Ni}} \right)}}^{*} \) and \( \tilde{D}_{{{\text{Ni}}\left( {\text{Ti - Al}} \right)}}^{*} \) increase with decreasing the Ni and Al compositions, respectively. The results imply that Al diffusion in β Ti-Al-Ni alloys would occur via an ordinary vacancy diffusion mechanism, whereas Ni diffusion, at least one order magnitude faster than Al, very likely benefits from interstitial diffusion as Fe and Co anomaly diffuse in BCC Titanium alloys.     

Comparative Oxidation Kinetics of a NiPtTi High Temperature Shape Memory Alloy

A high temperature shape memory alloy, Ni–30Pt–50Ti (at.%), with an M _s near 600 °C, was isothermally oxidized in air for 100 h over the temperature range of 500–900 °C. Nearly parabolic kinetics were observed in log–log and parabolic plots, with no indication of initial fast transient oxidation. On average the rates were about a factor of 4 lower than values measured here for a binary Ni–49Ti commercial SMA. The overall behavior could be best described by the Arrhenius relationships: $${\text{Ni}}{\text{Pt}}{\text{Ti}}{:}\,k_{\text{p}} = 1.54 \times 10^{12} \exp \left[(- 250\,{\text{kJ}}/{\text{mol}}) {RT} \right]{\text{mg}}^{2}/{\text{cm}}^{4} {\text{h}} $$ $${\text{Ni}}{\text{Ti}}{:}\,k_{\text{p}} = 6.39 \times 10^{12} \exp \left[(- 249\,{\text{kJ}}/{\text{mol}}) {RT} \right]{\text{mg}}^{2}/{\text{cm}}^{4} {\text{h}} $$ The activation energy was consistent with literature values for TiO₂ scale growth measured for elemental Ti and some NiTi alloys, at ~210–260 kJ/mol. However, a number of other studies produced activation energies in the range of 135–150 kJ/mol. This divergence may be related to various complex scale layers and depletion zones, however, no specific correlation can be identified at present.     

Bulk diffusion of iron in copper

The temperature dependence of bulk diffusion coefficient of iron in copper has been determined by electron microprobe analysis (EMA) in the temperature range from 923 to 1273 K to be $D_{Fe} = 0.03 \times 10^{ - 4} \exp \left( { - \frac{{187 kJ/mol}} {{RT}}} \right)$ m²/s. The results obtained differ from the parameters of bulk diffusion determined by the tracer method: the activation energy is less by 30 kJ/mol and the preexponential factor is less by approximately a factor of 50. The deviations of the solutions from the ideality does not explain the discrepancies obtained.     

Adsorption of ionic surfactants on water/air interface: One more transformation of the Gibbs equation

The adsorption of ionic surfactants on the water/air or water/hydrocarbon interface is considered. One form of the well-known Gibbs equation takes into account the surface excess of the amphiphilic ion in the compact layer, or monolayer, Γ ₂ ^m (2D adsorption), and the differential of the electrical potential of this layer. This expression is modified using some simplifying assumptions. The dependence of the surface tension, σ, on the activity of the amphiphilic ion, a ₂, degree of gegen-ions binding in the compact layer, β, and Γ ₂ ^m is transformed into the following relationship: $- \frac{{d\sigma }} {{RTd\ln a_2 }} = \Gamma _2^m \left\{ {2 - (1 - \beta )\frac{{d\ln \Gamma _2^m }} {{d\ln a_2 }}\left[ {\frac{1} {{\left[ {1 - \left( {\Gamma _2^m /\Gamma _2^{m\infty } } \right)} \right]^{1 + t} }} - \frac{{2b}} {{RT}}\Gamma _2^m } \right]} \right\}.$ Here Γ ₂ ^m denotes the Γ ₂ ^m value at complete filling of the adlayer, t = ?1, 0, or +1 for the two-phase model of partition, for immobile or mobile monolayer respectively, b is the cohesion constant; both the long-tailed ion and the gegen-ion are single-charged. The usefulness of the proposed equation is discussed.     

\left\{ {10\bar 12} \right\} twinning behavior in magnesium single crystal

In order to investigate $\left\{ {10\bar 12} \right\}$ tensile twinning behavior, the magnesium single crystal was deformed by compressing along the $\left[ {2\bar 1 \bar 10} \right]$ direction at room temperature, as $\left\{ {10\bar 12} \right\}$ tensile twinning easily takes place when the compression direction is perpendicular to the c-axis. Numerous $\left\{ {10\bar 12} \right\}$ primary tensile twins were activated during deformation, and the Schmid factor (SF) criterion was applied to the six $\left\{ {10\bar 12} \right\}$ twin variants. The analysis shows that the majority of the $\left\{ {10\bar 12} \right\}$ primary twins belong to high SF variants, and high SF twin boundaries provided nucleation sites for low SF variants. The $\left\{ {10\bar 12} \right\}$ secondary tensile twins were formed inside the high SF of wide $\left\{ {10\bar 12} \right\}$ primary twin bands, and the basal plane of the $\left\{ {10\bar 12} \right\}$ secondary twin was tilted about 60° with respect to the original parent matrix. In the case of the $\left\{ {10\bar 12} \right\}$ secondary tensile twin, relatively low SF variants were activated while counterparts with higher SF variants were absent.     

Electrochemical and Sulfide Stress Corrosion Cracking Behaviors of Tubing Steels in a H2S/CO2 Annular Environment

The electrochemical and sulfide stress corrosion cracking (SSCC) behaviors of 13Cr stainless steel and P110 steel were investigated in a simulated acidic annular environment with low-temperature and high-pressure H₂S/CO₂ using electrochemical methods, U-bend immersion tests, and scanning electron microscopy. In the solution containing high pressure CO₂, 13Cr, and P110 steels exhibited general corrosion and severe pitting, respectively. Compared with sweet corrosion, additional H₂S in the solution enhanced the corrosion of 13Cr steel but inhibited the corrosion of P110 steel. By contrast, in a solution containing 4 MPa CO₂ and different $ {P}_{{{\text{H}}_{ 2} {\text{S}}}}$ (0-0.3 MPa), the susceptibility of both 13Cr stainless steel and P110 steel toward SSCC was significantly promoted by increases in H₂S partial pressure. The 13Cr stainless steel exhibited higher susceptibility toward SSCC than P110 steel under a H₂S/CO₂ environment but lower susceptibility under a pure CO₂ environment.     

Oxidation of cobalt at high temperature

Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10^?4?0.658 atm). The dependence of the calculated values of parabolic rate constants k″_p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy E_k decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.     

Characterization of crystallographic properties of GaN thin film using automated crystal orientation mapping with TEM

The GaN thin film deposited on an amorphous glass substrate was analyzed by using transmission electron microscopy with a new automated crystal orientation mapping tool. Film deposition was made at 600°C for 4 h by the hyperthermal neutral beam (HNB) source. Columnar crystals oriented to the [0001] direction without significant disordering were clearly observed. Electron diffraction patterns indicated that the crystals have mainly two different zone axes, [2 $\bar 1$ $\bar 1$ 0] and [10 $\bar 1$ 0]. This crystallographic and microstructural information provides the guidance for future works for the HNB source to obtain GaN thin films of higher quality on amorphous substrates.     

Self-diffusion and defect structure in cobaltous oxide

The self-diffusion coefficients of cobalt in cobaltous oxide have been calculated from previously reported results of kinetics measurements of cobalt oxidation as a function of temperature and oxygen pressure. These results can be summarized by the following equation: $$D_{Co} = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{D}} /RT)$$ The activation energy of diffusion, E_D, increased with decreasing pressure, having values of 37 to 39.6 kcal/mole for oxygen pressures from 0.331 to 6.58×10^?4 atm, respectively, whereas the exponent 1/n decreased from 1/3.3 to 1/3.95 as the temperature increased from 950 to 1300°C. It was found also that above 1050°C the defects of the cation sublattice resulting from nonstoichiometry and the intrinsic Frenkel disorder overlap. Thus, at temperatures higher than 1050°C the deviations from stoichiometry cannot be regarded as an adequate measure of the concentration of point defects in cobaltous oxide.