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Platinum-rhodium (PtRh) alloy has excellent high-temperature mechanic properties and is one of the most promising materials for space engine thruster nozzles.The research has shown that the service life of space vehicles can effectively be extended by the high-temperature properties of PtRh alloys.In this study,the interfacial properties and bonding mechanism of TaC thermal barrier coating on the Pt25Rh high-temperature alloy were investigated by using a first-principles approach based on Materials Studio software.The results show that the thermal expansion coefficient of TaC is less different from that of Pt25Rh,and it has better interface matching and bonding force than similar thermal barrier ceramic coatings.In addition,the most stable bonding position from TaC to Pt25Rh alloy is Pt25Rh(111)/TaC(111) Cat the hole position,and the interfacial adhesion work is 6.202 J/m².This study can provide theoretical guidance for the development of PtRh high-temperature alloy. [ABSTRACT FROM AUTHOR]

New energy generation methods are currently being discussed with a view towards the transition from traditional primary sources to more environmentally friendly options, particularly renewables. Energy storage is also closely related to this transition. Battery storage currently dominates this area. However, flywheel energy storage system technology offers an alternative that transforms stored kinetic energy into mechanical and electrical energy using a motor generator. The flywheel energy storage system technology is thus flexible and can be applied in different industrial applications. The management of the technology of recycling tungsten multi-metallic composites (W-MMC) waste material from other products and the subsequent trial production of high-strength W-MMC material with a density of more than 17,500 kg/m3 from recycled powders allowed us to test the limits of the so-called "heavy" flywheels used in rotor production. The results achieved lead to the conclusion that the developed recycled materials of the W-MMC type with a density ≥17,500 kg/m3, with a yield strength of 1200–1700 MPa depending on the production method, can be used as a substitute for the structural steels used today without an enforced reduction in the maximum allowed rotor speed due to exceeding the maximum allowed stress. [ABSTRACT FROM AUTHOR]

New energy generation methods are currently being discussed with a view towards the transition from traditional primary sources to more environmentally friendly options, particularly renewables. Energy storage is also closely related to this transition. Battery storage currently dominates this area. However, flywheel energy storage system technology offers an alternative that transforms stored kinetic energy into mechanical and electrical energy using a motor generator. The flywheel energy storage system technology is thus flexible and can be applied in different industrial applications. The management of the technology of recycling tungsten multi-metallic composites (W-MMC) waste material from other products and the subsequent trial production of high-strength W-MMC material with a density of more than 17,500 kg/m3 from recycled powders allowed us to test the limits of the so-called “heavy” flywheels used in rotor production. The results achieved lead to the conclusion that the developed recycled materials of the W-MMC type with a density ≥17,500 kg/m3, with a yield strength of 1200–1700 MPa depending on the production method, can be used as a substitute for the structural steels used today without an enforced reduction in the maximum allowed rotor speed due to exceeding the maximum allowed stress.

A mechanistic understanding of the ductility limit diagrams is of critical importance, but it still remains elusive for a multitude of high temperature materials processing techniques, such as superplastic forming and hot forging. The relevant failure modes for the former are necking at high strain rates and intergranular cavitation at low strain rates, while those for the latter include the competition between longitudinal fracture and shear band. The comparison between the Arrhenius processes for grain boundary diffusion and grain interior creep defines a length scale that dictates whether the grain boundary cavity growth is diffusive or creep-constrained. A quantitative assessment of these damage evolution processes leads to the delineation of the dominant parametric spaces for individual failure modes, and thus superplasticity and forging limit diagrams are derived and compared to available experiments in literature. Ductility limits in high temperature processing of polycrystalline materials are analyzed from a quantitative assessment of intergranular cavity failure, as competing with necking and shear-band failure modes. The commonly believed practice of using high temperature and low strain rate to prevent high-temperature failure works for necking and shear band, but not for intergranular cavity failure. Excellent agreement with prior experiments which have not been mechanistically explained. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The knowledge of phase equilibria in RM-Si-B systems (RM = Refractory and/or Reactive Metals) is of great interest for the elaboration of thermodynamic databases, aiming the development of high temperature materials. Despite this, no experimental investigation is available in the literature concerning the liquidus projection of the Zr-Si-B system. Based on that, in this work, the liquidus projection of the Zr-Si-B ternary system was experimentally investigated in the Zr-ZrB2-ZrSi2 region via microstructural characterization of arc-melted alloys in the as-cast state using x-ray diffractometry and scanning electron microscopy. A proposal for the Zr-Si-B system liquidus projection is presented for the first time containing eight primary precipitation fields in which the ZrB2 prevails and no signs of a ternary phase was found. [ABSTRACT FROM AUTHOR]

In this paper, three kinds of W–Fe alloy models are constructed, namely W 15 Fe 1 , W 14 Fe 2 and W 13 Fe 3 alloys. By investigating the phonon spectra, it is found that W 13 Fe 3 alloy is thermodynamically unstable. Therefore, the mechanical and thermodynamic properties of W, W 15 Fe 1 and W 14 Fe 2 alloys are investigated based on first principles method. The investigation demonstrates that the bulk modulus of W 15 Fe 1 alloy increases rapidly with increasing temperature, exhibits high-temperature alloy characteristics. However, the bulk modulus of W 14 Fe 2 alloy decreases rapidly with increasing temperature, and is lower than that of W. The thermal expansion coefficient of W 15 Fe 1 alloy decreases with increasing temperature, and is significantly lower than that of W at 1400K, exhibits low expansion behavior at high temperatures. The thermal expansion coefficient of W 14 Fe 2 alloy increases rapidly with increasing temperature, and is obviously higher than that of W. The thermal conductivity of W 15 Fe 1 alloy exceeds that of W at 2300K, which indicates that doping an appropriate Fe in W can improve the thermal conductivity of W at high temperatures. However, the thermal conductivity of W 14 Fe 2 alloy is significantly lower than that of W and W 15 Fe 1 alloy. At 0K, doping Fe in W decreases the mechanical strength of W, but improves its ductility. • The bulk modulus of W 15 Fe 1 alloy increases rapidly with increasing temperature, exhibits high-temperature alloy characteristics. • The thermal expansion coefficient of W 15 Fe 1 alloy decreases with increasing temperature, and is significantly lower than that of pure W at 1400K, exhibits low expansion behavior at high temperatures. • The thermal conductivity of W 15 Fe 1 alloy exceeds that of W at 2300K, which indicates that doping an appropriate Fe in W can improve the thermal conductivity of W at high temperatures. • At 0K, doping Fe in W decreases the mechanical strength of pure W, but improves its ductility. • It is found that the adsorption energy of O is the smallest at the bridge site, which indicates that the bridge site is more sensitive to O adsorption. [ABSTRACT FROM AUTHOR]

In order to reduce the environmental impact of air travel, it is desirable that the efficiencies of gas turbine engines are increased. One way to achieve this goal is to increase the operating temperatures of the engine cores. Unfortunately for aero-engine manufacturers, the temperature capability limits of the Ni-base superalloys used currently have been reached. Hence, new alloys need to be developed that are capable of operating at significantly higher temperatures. In this article, the potential of tantalum-base superalloys is discussed and explored. A suite of alloys based on the Ta-Al-Co system was investigated. It was found that an array of fine carbide precipitates was formed in the Ta-rich matrix in a subset of the alloys, which is promising in terms of developing a strong and damage-tolerant microstructure, but that the elemental partitioning of Al out of the matrix accompanying precipitation is likely to degrade environmental resistance. Nevertheless, it is believed that the design principles described have the potential to facilitate the development of the next generation of high-temperature alloys based on systems of this type. • A suite of Ta-Al-Co alloys are designed and investigated. • Aim to produce BCC (A2) matrix + A2-superlattice precipitates. • Fine Ta3Al2CoC precipitates in Ta-rich BCC matrix found after ageing. • precipitates had a consistent orientation relationship with the matrix [ABSTRACT FROM AUTHOR]

Cast Ni-Si-B alloys have the potential for high-temperature applications because of their high resistance to wear, impact, corrosion, and oxidation at elevated temperatures due to an appropriate balance of hard phases and austenite that ensures a good compromise between toughness and hardness. In this work, NiSi3B2 specimens, fabricated by the lost-wax casting process, were investigated. Given the complex multiphase cast microstructure, a differential scanning calorimeter (DSC-TGA) analysis was employed to characterize the reactions that occur during solidification and the resulting phases were characterized using scanning electron microscopy (SEM), with energy-dispersive microanalysis (EDS) and backscattered electron (BSE) image and X-ray diffraction (XRD). Due to the presence of hard phases, machining of the Ni-Si-B components can pose additional difficulties. Therefore, the conditions of the solution heat treatment, which might lead to the homogenization of the microstructure, consequently improving its machinability, were also investigated. The results of the heat-treated samples indicated that the dissolution of the eutectic constituent is accompanied by a significant decrease in the hardness (approximately 17%). It is important to emphasize that the solution heat treatments carried out reduced the hardness without affecting the percentage of borides, which will allow improving the machinability without adversely affecting the alloy performance in service.

Five equiatomic alloys (TiZrHfVNb, TiZrHfVTa, TiZrNbMoV, TiZrHfMoV and ZrNbMoHfV) composed of five elements with high melting temperature, respectively were prepared by arc-melting to develop a novel high temperature alloy. The five alloys exhibit different dendritic and interdendritic morphologies. The TiZrHfVNb, TiZrHfVTa and TiZrNbMoV alloys formed disordered solid solution phases with body-centered cubic structure, and exhibited high compressive strength and good plasticity. The TiZrHfMoV and ZrNbMoHfV alloys are composed with Laves phase (HfMo2) and disordered solid solution phases with body-centered cubic structure. The TiZrHfMoV and ZrNbMoHfV alloys are harder and more brittle than the other three alloys due to the existence of hard and brittle Laves phases. At high temperatures, the strength decreases to below 300 MPa for the TiZrHfVNb and TiZrHfMoV alloys. Solution strengthening is the primary strengthening mechanism of the TiZrHfVNb, TiZrHfVTa and TiZrNbMoV alloys, and brittle Laves phase is the main cause for the low ductility of the TiZrHfMoV and ZrNbMoHfV alloys.

Microstructural stability and impact-toughness evolution of a Ni-Fe-based weld metal with different Cr contents was investigated during long-term thermal exposures up to 10000 h at 700 °C. With an increase in the Cr content from 21.1 to 23.5 at.%, plate-like sigma (σ) and α-Cr phases formed during the thermal exposure. These phases were mainly located in the interdendritic areas and grew significantly as the thermal exposure time increased. The coarsening process of the γ′ phase obeyed the Lifshitz, Slyozov, and Wagner (LSW) model, and the γ′ particles maintained a coherent relationship with the γ matrix during the thermal exposure. Carbides (M 23 C 6 ) formed and coarsened at the grain boundaries, and their distribution gradually transformed from discontinuous to continuous during the thermal exposure. The evolutions of the γ′ phase and M 23 C 6 carbides were not significantly affected by the Cr-content variation. As the thermal exposure time increased, the room-temperature impact toughness degraded significantly, and a ductile (intragranular)/brittle (mixed intergranular and intragranular) transition occurred. The degradation of impact toughness mainly occurred due to coarsening of the M 23 C 6 carbides along the grain boundaries and the growth of plate-like phases (σ, α-Cr) in the interdendritic areas. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of liquid Ag-Au-Ga alloys were determined using solid oxide galvanic cells with zirconia electrolyte: W, Ag x Au y Ga (1-x-y) , Ga 2 O 3 //ZrO 2  + (Y 2 O 3 )//FeO, Fe, W (I) in the temperature range from 1023 to 1348 K. Measurements were conducted in the ternary Ag-Au-Ga system along three cross-sections specified by the ratio of mole fractions x Ag / x Au  = 1:2, 1:1 and 2:1. Thermodynamic properties of the liquid phase were described with the Redlich-Kister-Muggianu formula. In this description procedure, the heat of mixing determined calorimetrically in the previous work was included. The results of the calculations were compared with the experimental data obtained in this work. [ABSTRACT FROM AUTHOR]

Pure tungsten is known to be a strong material but very brittle, due to its grain boundary structure. In a quest for improvement of the cold-work capacity of tungsten alloys, pure tungsten powder was doped with 1 wt% nickel. The mixture was consolidated by spark plasma sintering at temperature conditions below and above the Ni melting point. The addition of Ni tends to remove oxygen from W grain boundaries. Spherical particles of WO 2 are then formed when the sintering temperature is below the melting point of nickel; while tangled sticks of W oxide encapsulated by a submicron rim of Ni-rich phase are observed when the sintering is carried out above this melting point. Quasi-static compression tests at room temperature have been operated to assess the cold-working capacity of the obtained materials. Ni-doped materials sintered at a temperature below the Ni melting point revealed an increase in the strain at rupture by a factor of six approximately (12 % and 23 % in Ni-doped materials, whereas their W counterparts presents 1.9 % and 3.9 %, respectively), accompanied by a moderate decrease in the compressive strength (1300 and 1250 MPa, in respect with 1615 and 1325 MPa, respectively). The substantially improved mechanical properties of the Ni-doped samples is caused by the combination of the oxygen cleaning at the grain boundaries of the W matrix and local accommodation of the deformation by the created Ni-rich phase. The material consolidated at a temperature higher than Ni melting point underlines the formation of submicron thick ductile Ni-rich phase, accompanied with an improvement of both the strain at rupture and the compression strength of 3.5 times and 25 %, respectively. This configuration is expected to enhance the load transfer between the hard W matrix and the soft Ni-rich phases, which promote the activation of slip activity of the W matrix, in line with the extensive ductile phenomena distinctly observed on the ruptured specimens. [Display omitted] • The effect of Ni-doping on spark plasma sintering (SPS) of W alloys is studied. • SPS process is operated at one temperature below and above Ni melting point. • Every Ni-doped sample reveals the cleaning of GBs from O element. • Above Ni melting point, thin Ni-rich rims constrained by hard phases are formed. • This ductile Ni-rich phase also enhances the capacity to plastically deform. [ABSTRACT FROM AUTHOR]

The status of nanostructured ferritic alloys (NFAs) is summarized. The science underlying NFAs has emerged as a remarkably comprehensive and high quality body of research. The sequence of events and composition-processing paths needed to form and sustain the performance enabling nano-oxides are well established. The nano-oxides are predominantly Y 2 Ti 2 O 7 pyrochlore, and their role in providing outstanding mechanical properties and unique irradiation tolerance is described. Notably, however, producing defect-free NFA components remains a work in progress. The paper argues that the costs and supply of NFAs will be consistent with its selective application to advanced fission and fusion reactors. [ABSTRACT FROM AUTHOR]

This paper is about the three types of bcc Nb ss solid solution, namely normal Nb ss , Nb ss rich in Ti and Nb ss with no Si that are observed in multi-component Nb silicide based alloys of Nb-Si-TM-RM-X (TM = Cr, Hf, Ti, V, RM = Mo, Ta, W, X = Al, B, Ge, Sn) systems. The entropy (ΔS mix ) and enthalpy (ΔH mix ) of mixing, atomic size difference (δ), electronegativity difference (Δχ), valence electron concentration (VEC) and the parameter Q = T m ΔS mix /|ΔH mix | were calculated for fifty four solid solutions. The values of these parameters were −2 < ΔH mix < −15.9 kJ/mol, 5.8 < ΔS mix < 14.5 J/molK, 2.4 < δ < 9.7, 4.4 < VEC < 5.4, 0.039 < Δχ < 0.13 and 0.179 < Δχ < 0.0331 and 1.55 < Q < 8.9. The solid solutions with Δχ > 0.179 had no B, Ta and V and the solid solutions with no W had Δχ < 0.13. The atomic size difference parameter δ could separate the Nb ss rich in Ti (δ > 5) and the Nb ss with no Si (δ < 5). The formation of Ti rich Nb ss and Nb ss with no Si was attributed to the partitioning of Mo, Ti and W. [ABSTRACT FROM AUTHOR]

Co-Re alloys are being developed to supplement Ni-base superalloys in future gas turbines for ultra-high temperature applications. The finely distributed mono-carbide phase of TaC is an important strengthening phase in this alloy, and interacts with dislocations during high temperature creep deformation. This study aims to determine and to understand the volume fraction and size distribution of TaC precipitates in dependence of C/Ta stoichiometry and heat treatment by means of in-situ small-angle neutron scattering. At measuring temperatures of 1173 K, 1373 K and 1473 K, a stable population of fine TaC <100 nm size is formed during ageing for a wide range of C/Ta stoichiometry but with considerably different volume fraction and coarsening behavior. Important parameters for mechanical properties of the material, such as particle size distribution and inter-particle distance, were determined. It is shown that the phase transformation from γ-matrix (fcc) ↔ ε-matrix (hcp) of the Co-Re matrix has a considerable influence on the TaC precipitate formation. [ABSTRACT FROM AUTHOR]

Additive manufacturing is enabling a paradigm shift in design and production, but conventional techniques reach their limits when metallic structures require walls with < 0.5 mm thickness. Here we introduce an approach for indirect additive manufacturing of thin-walled alloy structures. First a polymer template is additively manufactured, then metal layers are deposited by electroplating, physical or chemical vapor deposition. After removal of the polymer, the metal layers can be interdiffused to form an alloy via homogenization heat treatments. Three different alloys designed for three elevated temperature regimes are demonstrated: Monel alloys based on Ni-Cu-Al-Ti, nickel superalloys based on Ni-Cr-Al and refractory rhenium alloys based on Re-Co. A process was developed to co-deposit rhenium and cobalt via aqueous electroplating, resulting in an alloy with a melting point of 2000 °C and a Vickers hardness of 480 ± 50 HV 0.2 after homogenization. Two applications of interest for the aerospace industry were chosen to demonstrate the technology. High temperature truss core sandwich structures and rocket engine thruster demos where fabricated. [ABSTRACT FROM AUTHOR]

The microstructures and mechanical properties of as-cast Ti-Mo-Al alloys with various compositions were systematically investigated in this study, aiming to explore the potentials of B2-ordered phase (β 2 ) in high temperature applications. According to the experimental results, these as-cast Ti-Mo-Al alloys were mainly composed of β 2 phase and contained a large number of dislocation walls and sub-grain boundaries. Overall they exhibited a high level of compressive strength at 1073 K, with the maximum value approaching ∼879 MPa. The impressive mechanical properties of β 2 -dominating Ti-Mo-Al alloys are related to the excellent stability of B2 structure and extensive dislocation entanglements at elevated temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Buckingham-Pi-Theorem-based fatigue life prediction models that employ both stress-based and stress–strain-based criteria are proposed. • The models are validated using data pertaining to 16 industrial alloys, taken from NIMS (National Institute of Materials Science, Tsukuba, Japan) database. • Accurate predictions are obtained for the range of 103 to 10 8 fatigue life cycles, tested at different temperatures, within and outside the regions governed by Paris equation. • It is conjectured that the models can be adapted beyond the fatigue cycle range and temperatures tested and could be used to study the behaviour of other materials also. A robust, quantitative analysis is needed to prevent frequent, catastrophic failure of components in powerplants and aircraft, to cite but two examples, due to cyclic loading that could lead to fatigue failure. The model presented in this research will be useful in the reliable design and safe operation of components and equipment. A fatigue life (the dependent variable) prediction model, which employs both stress-based, and stress–strain based criteria is presented that uses the Buckingham Pi Theorem with the experimental parameters influencing fatigue behaviour taken as the independent variables. The validation of the model is done using reliable, frequently used uniaxial fatigue data, culled from the NIMS (National Institute for Materials Science, Tsukuba, Japan) fatigue database on important industrial alloys that experience fatigue loading in service. (No reliable data on such a scale were available to test the validity of this model under multi-axial fatigue loading conditions.) It is demonstrated that the model predicts the experimental results accurately. The accuracy of prediction is examined for every case and compared with that of some other existing methods. Moreover, the potential applicability of this analysis in areas not yet validated is examined. [ABSTRACT FROM AUTHOR]

A combined technique denoted as seeding-grain selection (SGS) was designed for fabricating single crystal turbine blades. The microstructural evaluation during SGS process was metallographically analyzed in both starter section and spiral section of this technique. Four zones with distinct dendritic morphologies were identified in seed melt back region. After epitaxial propagating from melted seed and branching through the spiral passage, the lined-up dendritic pattern was observed at the outlet of the passage. The effectiveness of the technique on stray grain and orientation control was also assessed by Electron Back-Scattering Diffraction (EDSD) technique. The results indicated that the technique can control stray grain with no detrimental effect on crystal orientation. [ABSTRACT FROM AUTHOR]

Precipitation of γ' phase in nickel-base superalloy IN792-5A was studied using in-situ Small Angle Neutron Scattering (SANS). It was found that additional precipitates are formed after reheating above 600 °C when the material is previously fast cooled (100 K/min) from 900 °C. The size distribution and volume fraction of the additional y' precipitates as well as of the already present medium-size precipitates in dependence on temperature were evaluated. The small precipitates can influence mechanical properties of the alloy, which exhibits an anomaly in the temperature dependence of the yield stress. Volume fraction of all precipitate populations above 900 °C was estimated as well. [ABSTRACT FROM AUTHOR]

Dynamic strain aging was observed in the temperature range between 300 °C and 500 °C in a near α titanium alloy 834 without Silicon (10.38%Al–0.16%Sn–1.86%Zr–0.37%Nb–0.25%Mo–0.27%C–0.30%O–0.006%N, all in at%) tested in the temperature range from room temperature to 500 °C. Electron microscopic investigation of tensile tested samples in an energy filtered transmission electron microscopy provided direct experimental evidence for segregation of interstitial elements like carbon (C) and nitrogen (N) to lath boundaries and dislocation pile ups. On the basis of these results and the comparison of lattice strain generated by different interstitials in α -Ti, it was concluded that segregation of carbon and nitrogen and not oxygen to defects is responsible for DSA in this alloy. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of liquid (Sb + Sn) and (Au + Sb + Sn) alloys were determined using solid oxide galvanic cells with zirconia electrolyte: (I) Re + kanthal, Sb x - Sn ( 1 - x ) , SnO 2 / / ZrO 2 + ( Y 2 O 3 ) / / NiO,Ni,Pt, (II) Re + kanthal, Au x - Sb y - Sn ( 1 - x - y ) , SnO 2 / / ZrO 2 + ( Y 2 O 3 ) / / NiO,Ni,Pt, over the temperature range from (973 to 1273) K. Using the Gibbs free energy of formation of pure solid tin oxide SnO 2 , at first the activities of tin were determined in the binary (Sb + Sn) system. Next, measurements were conducted in the ternary (Au + Sb + Sn) system along two cross-sections specified by the ratio of mole fractions x Au / x Sb = 1:2 and 2:1. Thermodynamic properties of the liquid phase were described by the Redlich–Kister–Muggianu formula. In this procedure, the heat of mixing determined in our previous paper was included. The results of the calculations were compared with the experimental values obtained for this system. [ABSTRACT FROM AUTHOR]

The deformation and the recrystallization initiation in the dendrite core and interdendritic regions were investigated by employing microhardness tester, optical microscope, scanning electron microscope and electron backscatter diffraction technique. It was found that different recrystallization nucleation mechanisms operated in the dendrite core and interdendritic regions. Recrystallization nucleation may take place by strain induced boundary migration in the dendrite cores, while particle stimulated nucleation occurs in the interdendritic regions. The deformation and the recrystallization initiation in the dendrite core and interdendritic regions were compared and discussed. The role of the carbides and eutectics in particle stimulated nucleation was also clarified. [ABSTRACT FROM AUTHOR]

Surface tension influences the processing of molten metals including welding, soldering, refining, and casting, but it is challenging to measure at high temperatures, and thus it is an important property to predict. In particular, the surface tension of metal alloys is crucial to predict as a function of alloy composition and temperature. Previously, we developed the Shardt–Elliott–Connors–Wright (SECW) model that has the advantage of being able to predict the surface tension of mixtures as a function of composition and temperature using as inputs only the temperature dependence of pure components and the composition dependence at a single reference temperature. This model has been shown to be accurate for a broad range of non-metal mixtures. In this work, we extend the applicability of our model to six metal alloy systems, resulting in an absolute average percent deviation from experimental measurements of 1.9% over all studied compositions and temperatures ranging between 513 K and 1503 K (419 experimental data points). [Display omitted] • Accurate prediction of metal alloy surface tension at elevated temperatures. • Minimal amount of experimental data needed as input to our model. • All model parameters tabulated for straightforward implementation in applications. [ABSTRACT FROM AUTHOR]

Characterization of the early stage precipitation is an important issue as it controls the emerging microstructure developed on Ni-based superalloys which are used as single crystal blades in gas turbines. The difficulty is that the gamma prime precipitation occurs at high temperatures and the reaction kinetic is very fast. Therefore, experimental methods with high time resolution are needed to monitor γ' precipitation. By using the high flux synchrotron instrument HARWI-II set up of the Helmholtz-Zentrum Geesthacht with a fast data collection detector, it was possible to observe the creation of fine precipitates and their early growth in a tungsten-rich Ni-base superalloy. The cooling down of the superalloy from the single-phase region to lower temperatures already leads to the formation of precipitates in the size range of a few nm. The formation and growth of the precipitates at this early stage is described in detail. In addition, SANS measurements were performed at the new SANS-1 instrument at Maier-Leibnitz Zentrum (MLZ) in Garching to extend the results to larger precipitate sizes. DSC experiments were used to determine the critical temperatures of the formation of these fine precipitates, as well as the temperature at which they dissolve during heating (γ' solvus temperature). [ABSTRACT FROM AUTHOR]

Highlights: [•] Formation of a multi-layered scale. [•] Formation of NiO in a NiAl containing alloy. [•] Formation of NiAl2O4 in a NiAl containing alloy. [•] Oxidation mechanism is significantly different from Ni–Mo alloys. [ABSTRACT FROM AUTHOR]

Precipitation of γ’ phase in nickel-base superalloy IN792-5A was studied using in-situ Small Angle Neutron Scattering (SANS). It was found that additional precipitates are formed after reheating above 600 °C when the material is previously fast cooled (100 K/min) from 900 °C. The size distribution and volume fraction of the additional γ’ precipitates as well as of the already present medium-size precipitates in dependence on temperature were evaluated. The small precipitates can influence mechanical properties of the alloy, which exhibits an anomaly in the temperature dependence of the yield stress. Volume fraction of all precipitate populations above 900 °C was estimated as well.

Highlights: [•] Evolution of γ′-phase morphology in IN738LC Ni-base superalloy was examined by SANS. [•] In situ tests at high temperatures revealed trimodal precipitate distribution. [•] Formation, dissolution and (slow) kinetics of small γ′ precipitates was determined. [•] Equilibrium volume fraction of γ′ phase is significantly higher than 45%. [•] The small γ′ precipitates arise regardless the application of the mechanical load. [Copyright &y& Elsevier]

Highlights: [•] Disordered BCC phase in Al0.9–Al1.0 alloys transforms into FCC and σ phases at 873K. [•] FCC and σ phases form in an associated manner from the Fe,Cr-rich BCC phase. [•] The σ phase connected with the FCC phase are formed from disordered BCC phase. [•] The T T range of the Al x alloys is at 810–930K which is about 0.5T m of the alloys. [•] The Al x alloys with x ⩾0.5 is slip below the T T and creep deformation above the T T. [Copyright &y& Elsevier]

The dependence of the creep rupture strength on the microstructure of a liquid metal cooling directionally solidified nickel based superalloy was investigated over a wide range from 980 to 1100°C. The creep rupture lives were prolonged especially at 980°C/310 MPa as a result of the elimination of the blocky primary γ′. The fractured specimens were sectioned and examined to reveal the deformation microstructures and active dislocation deformation mechanisms. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate the feasibility of preparation of Nb10Hf1Ti alloy by magnesiothermic reduction of its oxides. DTA studies were conducted to identify the reduction temperature for co reduction of the mixed oxides of NbO, HfO, and TiO by magnesium under reducing atmosphere. Based on DTA analysis, experiments were carried out to prepare Nb10Hf1Ti alloy by magnesiothermic reduction of their oxides at 750 °C. The reduced product was analyzed for its phases by X-ray diffraction. The excess Mg was leached out, the alloy mixture was vacuum dried, pelletized, sintered, and electron beam melted to get a consolidated alloy of the required composition. The alloy was characterized using different techniques such as optical microscopy, scanning electron microscopy, and chemical analysis. Microstructural observations revealed the formation of coarse grain structure in the consolidated alloy. The alloy product was also evaluated for its micro hardness. [ABSTRACT FROM AUTHOR]

Abstract: The tensile behaviour of boron modified Timetal 834 titanium alloy was studied in the intermediate temperature range 400–500°C and compared with that of the base alloy. The yield and ultimate tensile strengths of the B modified alloy were found to be higher than those of the base alloy at all the temperatures investigated. The B modified alloy also exhibited only a marginally lower elongation to failure as compared to the base alloy at all the temperatures investigated. The B modified alloy exhibited dynamic strain aging in the temperature range 400–475°C which is similar to the observed behaviour in the base alloy. [Copyright &y& Elsevier]