[en] Design of advanced materials in general calls for better understanding of phase transitions at service temperatures and relevant equilibrium phase diagrams. In the case of multicomponent alloys, it is often necessary to study phase transformations on model systems. Ni-Al-Cr-X quaternary systems (X = Co, W, Ti, Ta, etc.) are relatively simple yet sufficiently representative models for Ni-base superalloys. However, their complete thermodynamic description requires qualified knowledge of thermodynamic parameters for lower order systems as well as higher order correction terms. This work continues our previous studies on Ni-Al-Cr-(Co, W, Mo) systems. This time it is focused on titanium as the fourth element. Experimental alloys were prepared with respect to γ + γ' phases presence and studied by means of analytical electron microscopy after annealing at typical service temperatures. Experimentally identified types of phases are compared with those obtained by means of thermodynamic calculations

[en] Microstructural changes in a metallic oxidation protection coating (Ni-Co-Cr-Al-Y) applied on a nickel base superalloy were investigated by means of scanning and transmission electron microscopy. The changes are due either to thermal mechanical fatigue testing under high thermal gradients or to defined isothermal heat treatments. The coated specimens were quenched from temperatures between 840 and 1100 deg. C to ambient temperature. The resultant phases, their local distribution and compositions were determined by energy dispersive X-ray (EDX) spectroscopy and electron diffraction. Phase equilibria at respective temperatures were determined by thermodynamic calculations based on the CALPHAD method. The calculated and experimentally determined phase distributions were compared. A particular microstructural feature, namely the existence and spatial distribution of spherical γ' Ni₃Al precipitates in the coating and the diffusion zone between substrate and coating, was used as a postmortem indicator for the maximum temperature experienced by the specimen during testing. This paper gives a road map for developing a microstructural-based temperature calibration for complex metallic materials using thermodynamic simulations

[en] The existing assessment of thermodynamic and phase equilibrium data in the Ag-Pd system was revised on the basis of calorimetric data for liquid Ag-Pd alloys published recently in the literature and on new determination of liquidus and solidus temperatures and activity data for Ag in liquid phase, using differential scanning calorimetry (DSC) coupled with Knudsen cell mass spectrometry (KC/MS). A substantially narrower liquid/fcc two-phase field in phase diagram as well as new non-ideal activity data were revealed.

[en] Four-layer telescopic silicon strip detectors based on PH32 chip technology were developed at FJFI CVUT in Prague and manufactured by esc Aerospace in Prague. They are capable of filtering particles so that an event is recorded only in the case when the detector response is non-zero in all 4 layers at the same time, i.e. there is a high probability that just 1 particle flew through the layers, most often a muon. The type of particle can be estimated by the amount of energy it leaves in the detector, i.e. the magnitude of the response of the detector in a given layer. The strip structure of the detector also makes it possible to determine the angles of individual particles. This work mainly deals with the measurement of muons in the CERF field (The CERN-EU high-energy Reference Field facility) - their angular distribution and the comparison of the frequency measured by different strip detectors and the ionization chamber permanently located at the measurement site in the CERF facility. Furthermore, the results from measurements of angular distributions and frequencies of muons on board aircraft and their comparison with the model will be presented. (authors)

[en] Highlights: ► We study the phase diagram Bi–Ni–Sn by using scanning electron microscopy and differential scanning calorimetry. ► The samples are positioned in 3 isopleths with constant Ni contents of 0.05, 0.10 and 0.15 mol fraction. ► It has been confirmed that a ternary eutectic reaction appears at around 116–129 °C. ► Experimental liquidus temperatures were obtained and compared to calculated ones. ► Six groups of thermal arrests were registered (except the eutectic and liquidus related peaks). - Abstract: The phase diagram Bi–Ni–Sn was studied by means of SEM (scanning electron microscopy)/EDS (energy-dispersive solid state spectrometry), by DSC (differential scanning calorimetry) and RT-XRD (room temperature X-Ray diffraction) in order to attain more information about this ternary phase diagram. The samples were positioned in three isopleths with nickel contents of: 0.05 (section 1), 0.10 (section 2) and 0.15 (section 3) mole fractions, respectively. The mole fractions of Sn corresponding to the particular sections were as follows: from 0.19 to 0.76 (section 1), from 0.18 to 0.72 (section 2); from 0.17 to 0.68 (section 3). Mixtures of pure metals were sealed under vacuum in amorphous silica ampoules and annealed at 350 °C. A binary Bi–Sn eutectic sample was synthesized and used as internal standard. The existence of a previously reported ternary eutectic reaction was confirmed. Liquidus temperatures were identified and the results were compared to CALPHAD-type calculations. It was found that ternary samples’ liquidus temperatures were higher than the calculated ones. Six more groups of thermal arrests were registered except the eutectic and liquidus related peaks.

[en] Highlights: → Sn-Zn-Ni phase diagram in the vicinity of the Sn-Zn system. → Unidentified compositions (UX1-UX4) are repeatedly observed. → This indicates up to 6 ternary compounds in the system. → A ternary eutectic reaction at around 190 ^oC is found. - Abstract: The phase diagram Sn-Zn-Ni was studied by means of DSC and electron microprobe analysis. The samples were positioned in three isopleth sections with nickel contents of 0.04 (section 1), 0.08 (section 2) and 0.12 (section 3) mole fractions. The mole fractions of Sn corresponding to the particular sections were as follows: from 0.230 to 0.768 (section 1), from 0.230 to 0.736 (section 2); from 0.220 to 0.704 (section 3). Mixtures of pure metals were sealed under vacuum in quartz ampoules and annealed at 350 ^oC. The solid phases identified in the samples were: γ-(i.e. Ni₅Zn₂₁), (Zn) and the ternary phase T1. Unidentified compositions were observed. One of them: UX1 (X_Ni = 0.071 ± 0.005, X_Sn = 0.439 ± 0.009 and X_Zn = 0.490 ± 0.010) might indicate another (stable or metastable) ternary compound (T3) in the system Sn-Zn-Ni. Considering the data obtained by combining DSC with microstructure observations, the studied alloys could be divided in two groups (A and B). A ternary eutectic reaction at around 190 ^oC is common for the A-group alloys. The phases taking part in this reaction are, probably, Ni₅Zn₂₁, (Zn), (βSn) and liquid. B-group samples do not show ternary eutectic reaction and are also characterized by the presence of the ternary compound T1 (absent in the A-group alloys). Four other groups of thermal arrests were registered (TA₁-TA₄). It was found that TA₂ peaks were characteristic for most of the A-group samples, while TA₁ peaks were registered with all B-group samples.

[en] Highlights: ► The phase transitions of the Higher Manganese Silicides were investigated. ► The samples were characterised by XRD, DTA and DSC. ► Mn₂₇Si₄₇ is the stable phase at room temperature and under atmospheric pressure. ► At around 800 °C, Mn₂₇Si₄₇ is transformed into Mn₁₅Si₂₆. ► The phase transition is of a second order. - Abstract: This work is an investigation of the phase transformations of the Higher Manganese Silicides in the temperature range [100–1200 °C]. Several complementary experimental techniques were used, namely in situ X-ray Diffraction (XRD), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The evolution of both the lattice parameters and the thermal expansion coefficients was determined from in situ XRD measurements. The stability of the samples was investigated by thermal analysis (DTA) and Cp measurements (DSC). This study shows that Mn₂₇Si₄₇ which is the stable phase at room temperature and under atmospheric pressure undergoes a phase transformation at around 800 °C. Mn₂₇Si₄₇ is transformed into Mn₁₅Si₂₆. This phase transformation seems to be of a second order one. Indeed it was not evidenced by DTA and by contrast it appears on the Cp curve.

[en] Phase relations have been evaluated for the Ta–V–Si system at 1500 and 1200 °C. Three ternary phases were found: τ₁-(Ta,V)₅Si₃ (Mn₅Si₃-type), τ₂-Ta(Ta,V,Si)₂ (MgZn₂-type) and τ₃-Ta(Ta,V,Si)₂ (MgCu₂-type). The crystal structure of τ₂-Ta(Ta,V,Si)₂ was solved by X-ray single crystal diffraction (space group P6₃/mmc). Atom order in the crystal structures of τ₁-(Ta,V)₅Si₃ (Mn₅Si₃ type) and τ₃-Ta(Ta,V,Si)₂ was derived from X-ray powder diffraction data. A large homogeneity range was found for τ₁-(Ta_xV_1−x)₅Si₃ revealing random exchange of Ta and V at a constant Si content. At 1500 °C, the end points of the τ₁-phase solution (0.082≤x≤0.624) are in equilibrium with the solutions (Ta_1−xV_x)₅Si₃ (Cr₅B₃ type, 0≤x≤0.128) and (Ta_xV_1−x)₅Si₃ (W₅Si₃ type, 0≤x≤0.048). - Graphical abstract: Phase relations have been evaluated for the Ta–V–Si system at 1500 and 1200 °C. Highlights: ► Phase relations have been evaluated for the Ta–V–Si system at 1500 and 1200 °C. ► Three ternary phases were found at 1500 °C. ► At 1500 °C, τ₁-phase has large homogeneity region (0.064≤x≤0.624).

[en] Highlights: • First time to define experimental mechanical and physical properties of TiMn₂. • Defines for the first time the thermodynamic stability of refractory TiN with respect to Ti-Mn alloys. • Ti-Mn brazing alloys in stable contact with TiN diffusion barrier in thermoelectric devices. Mechanical (elastic) properties have been derived for polycristalline TiMn₂ from micro-indentation and thermal expansion measurements. With a room temperature (RT) Vicker's hardness of ∼11 GPa, TiMn₂ is a rather hard intermetallic material. The elastic modulus is E = 217 ± 4 GPa at RT. Physical properties (from 1.8 K to 300 K) including specific heat, electrical resistivity and magnetic susceptibility reveal temperature independent paramagnetism and metallic conductivity consistent with a Bloch-Grüneisen behavior. Based on experimental data (X-ray powder diffraction, metallography, SEM and EMPA on 30 alloys prepared by various methods employing arc melting, powder reaction sintering in closed crucibles as well as nitriding binary master alloys in 10⁵ Pa nitrogen gas) phase relations in the ternary system Ti-Mn-N have been established and calculated for the isothermal section at 900 °C. The thermodynamic modelling relies on existing thermodynamic assessments of the Mn-N and Ti-N binary systems and on our recent modelling of the Ti-Mn system, which is characterized by a significantly higher thermodynamic stability of the C14-type Laves phase Ti_1-xMn_2+x than hitherto assumed in the literature. It is this higher stability, which is consistent with the experimental phase triangulation in Ti-Mn-N: as the most important consequence of the higher stability of Ti_1-xMn_2+x, compatibility exists between the only two congruently melting compounds Ti_1-xMn_2+x and TiN_1-x. The high melting refractory solution TiN_1-x dominates the liquidus surface pushing all monovariant melting lines close to the Ti-Mn binary.