Creep Resistance Of Alloy Research Articles

Effect of eutectic microstructure on load transfer and creep resistance in Al-Ce alloys

This study investigates the compressive creep response of hypo- and near-eutectic Al-Ce alloys via finite-element modeling (FEM), by considering the composite response of a weak, fast-creeping Al matrix containing slow-creeping Al11Ce3 eutectic reinforcement. In the as-cast microstructure of an eutectic Al-12.5 wt%Ce alloy, the Al11Ce3 eutectic phase is lamellar, regardless of the various cross-sectional geometries (Chinese-script, fish-bone, and comb-like). FEM models based on these various lamellar microstructures investigate the effect of Al11Ce3 reinforcement volume fraction, orientation, and geometry on load transfer performance between matrix and reinforcement during creep deformation. FEM predicts that, when the lamellar Al11Ce3 phase is continuous along the loading direction (where load transfer is most effective), the creep resistance of the alloy is barely affected by cross-sectional geometry of the Al11Ce3 reinforcement or by the solid-solution strengthening of the Al matrix, at constant Al11Ce3 volume fraction. However, alloy creep resistance and load transfer between phases are significantly reduced when applying load parallel to aligned, discontinuous lamellae, and they can be improved by matrix solid-solution strengthening. Furthermore, Al11Ce3 short plates (as created in Al-12.5Ce by coarsening of lamellae upon over-aging at 590 °C/24 h) provide the least creep resistance and load transfer. Lastly, multi-colony FEM models are created by combining colonies with various lamellar orientations to approximate the creep performance of polycrystalline hypo- and near-eutectic alloys which, when compared to experimental data for hypoeutectic Al-7Ce and for near-eutectic Al-(10–13)Ce, provide better predictions than single-colony FEM models or analytical solutions.

Розроблення жароміцних ливарних сплавів на основі системи Al-Fe-Mn-Ni

Development of new creep-resistant materials is a constantly existing task for modern materials science. At the same time, the creation of creep-resistant aluminum alloys plays an important role due to the combination of low density and the potential to achieve high resistance to properties degradation unter elevated temperatures. Increasing the level of operating temperatures for aluminum alloys makes it possible to replace some of the parts made of iron-based materials in cars, airplanes and various machinery. This will allow to reduce the weight of machines and mechanisms, increase their energy efficiency and environmental friendliness due to the reduction of carbon dioxide emissions. Most of the widely used creep-resistant aluminum alloys belong to the Al-Si-Cu, Al-Cu and Al-Si-Cu-Fe-Ni systems. Such alloys have a relatively low level of mechanical properties, which is insufficient for modern requirements. Their significant advantage is the ease of obtaining finished products by using casting processes. Among the alternative systems of heat-resistant aluminum alloys, those containing Fe, Ni, Cr and Mn are often considered. Iron and nickel are able to form fibrous nano-sized components of eutectics with aluminum, which are stable at high temperatures. They are effective barriers for the movement of dislocations and they also do not eliminate alloys plasticity. The disadvantage of such alloys is the zero alloying of the matrix metal, which means potentially low strength. Alloying of heat-resistant aluminum alloys should be carried out with elements that have a low diffusion coefficient in aluminum. The best option for this is manganese, which can dissolve in Al-matrix in a large quantities and forms a stable strengthening intermetallic Al6Mn with aluminum. Al-Fe-Mn-Ni alloys, because of their structural and phase features, can be subjected to plastic deformation, which, in combination with heat treatment, significantly increases the level of mechanical properties of alloys in a wide temperature range due to grain refinement and inhibition of recrystallization by stable ultradispersed intermetallic particles. Keywords: сasting aluminum alloys, creep-resistant alloys, new materials, Al-Fe-Mn-Ni.

Жароміцні інтерметалідні сплави та особливості їх легування

The work considers the prerequisites for the development of creep-resistant and heat-resistant alloys, based on intermetallics, taking into account the optimal combination of their physical and mechanical properties, as well as structural characteristics. It is shown that there is a sufficient number of intermetallics, which have a density lower than iron-based alloys, which, in combination with high melting temperatures and heat resistance, makes them promising materials for aerospace application, in particular, for gas turbine engine parts manufacturing. The most suitable creep-resistant and heat-resistant intermetallics can be called aluminides and silicides of titanium, nickel and molybdenum. For these compounds, it is possible to combine high values of specific strength with alloying-favorable types of crystal lattice. One of the most important and common creep-resistant alloys based on intermetallics is Ni3Al with FCC lattice. For this material, complex optimized alloying is the main way to increase creep resistance. The heat resistance of such alloys is significantly increased by applying ceramic coatings. Titanium aluminides Ti3Al and TiAl mainly have only a low density among the advantages. Their fragility at room temperatures and tendency to superplasticity at high temperatures significantly limits their application. The impact of disadvantages may be reduced by applying thermomechanical processing of such materials, which aims to change their structure. Alloying titanium aluminides with a large amount of niobium was chosen as a solution that significantly reduced marked week sides of Ti-Al intermetallic alloys. As a result, this led to the creation of a new alloy based on intermetallic Ti2AlNb with a high set of operational characteristics. Mo-Si and Mo-Si-B can be considered as one of the most perfect systems for creating heat-resistant intermetallic alloys. They combine an acceptable density, high creep and heat resistance, which can be additionally increased by reinforcing with ceramic particles. Keywords: intermetallic-based alloys, creep resistance, alloying, Ni-Al, Ti-Al, Mo-Si, Mo-Si-B.

Recent Progress in Creep-Resistant Aluminum Alloys for Diesel Engine Applications: A Review.

Diesel engines in heavy-duty vehicles are predicted to maintain a stable presence in the future due to the difficulty of electrifying heavy trucks, mine equipment, and railway cars. This trend encourages the effort to develop new aluminum alloy systems with improved performance at diesel engine conditions of elevated temperature and stress combinations to reduce vehicle weight and, consequently, CO2 emissions. Aluminum alloys need to provide adequate creep resistance at ~300 °C and room-temperature tensile properties better than the current commercial aluminum alloys used for powertrain applications. The studies for improving creep resistance for aluminum casting alloys indicate that their high-temperature stability depends on the formation of high-density uniform dispersoids with low solid solubility and low diffusivity in aluminum. This review summarizes three generations of diesel engine aluminum alloys and focuses on recent work on the third-generation dispersoid-strengthened alloys. Additionally, new trends in developing creep resistance through the development of alloy systems other than Al-Si-based alloys, the optimization of manufacturing processes, and the use of thermal barrier coatings and composites are discussed. New progress on concepts regarding the thermal stability of rapidly solidified and nano-structured alloys and on creep-resistant alloy design via machine learning-based algorithms is also presented.

Grain refinement and exceptional creep resistance achieved in an as-cast Mg–Y alloy with Al addition

Grain refinement strengthening is crucial for Mg alloys. However, refined grains can facilitate grain boundary migration during high-temperature creep, usually unfavorably affecting high-temperature creep properties. Al was incorporated into Mg–Y alloy to address this trade-off between fine-grained structures and creep properties, causing the refinement of the Mg–Y alloy (average grain size of 73.2 ± 2.9 μm) while maintaining excellent creep resistance. At 300 °C/50 MPa, the Al-refined alloy exhibited the minimum creep rate of 1.31 × 10−8 s−1, representing a 62 % reduction compared to that of the Mg–Y alloy without Al refinement. During high-temperature creep, the thermally stable Al2Y and long-period stacking ordered (LPSO)/stacking faults (SFs) phases introduced by Al addition effectively pin grain boundaries and impede dislocation movement, which could thus enhance the alloy's creep resistance. Meanwhile, Al addition reduces stacking fault energy (SFE), rendering dislocation climb more challenging and further enhancing the alloy's creep resistance. This study employs Al to refine Mg–Y alloys, achieving grain refinement while enhancing creep resistance, providing a novel method for developing Mg-RE alloys with both refined grains and creep resistance.

A new tensile creep model for predicting long-term creep strengths with short-term test data for creep resistant alloys

The difficulties in using the conventional Norton creep model to rationalise short-term creep data and to subsequently predict long-term creep rupture strengths for creep resistant alloys are presented and analysed. The results of this study show that these difficulties can be resolved if a new tensile creep model that integrates the tensile strength at creep temperature is applied to rationalise the short-term creep data. This is illustrated with the creep and tensile strength data measured for a grade of Ni-based superalloy. Based on this new tensile creep model, the activation energy of creep determined is independent of stress and the stress exponent is not influenced by temperature. Consequently, the model constants obtained from the short-term creep data can be applied together with the Monkman-Grant relationship to make the long-term creep rupture strength predictions at different temperatures. The factors affecting the reliability of the predictions made by this method are also analysed.

BÖHLER L306 VMR

Abstract Böhler L306 VMR is a wrought, age-hardenable nickel-chromium alloy, strengthened by additions of titanium, aluminum, and carbon. It has been developed as a creep-resisting alloy for service at temperatures up to 815 °C (1500 °F). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming and heat treating. Filing Code: Ni-785. Producer or source: voestalpine Böhler Edelstahl GmbH & Co KG.

High-temperature failure and microstructural investigation of wire-arc additive manufactured Rene 41

In developing a wire-arc plasma direct energy deposition process for creep-resistant alloys used in high-speed flight applications, structures were built from nickel-based superalloy Rene 41. Samples of additive manufacturing (AM) material were analysed for their microstructural and mechanical properties, in both as-deposited (AD) and heat-treated (HT) conditions. Tensile specimens were tested at room temperature, 538, 760, and 1000 °C. Macroscopically, large columnar grains made up of a typical dendritic structure were observed. Microscopically, significant segregation of heavier elements, grain boundary precipitates, and secondary phases were observed, with key differences observed in HT material. There was a clear distinction between failure modes at different testing temperatures and between AD and HT variants. A fractographic investigation found a progressive move from brittle to ductile fracture with increasing testing temperature in both AD and HT conditions, as well as microstructural features which support this observation.

Experimental investigation on microstructural characterization and mechanical properties of plasma arc welded Inconel 617 plates

Abstract Welding of Inconel is a difficult task due to its tendency to crack and posing intricacies to the welder. However, it is extensively used in applications where resistance to oxidation at elevated temperatures is required. Therefore, it is important to note that the welding of Inconel alloys is demanding. Under such circumstances, one has to automate the welding of Inconel 617 alloy to eliminate some of the process uncertainties. Plasma arc welding (PAW) is a highly non-linear process that can be automated easily, and it can provide more focussed arc to weld the high strength and creep-resistant alloys. In the present research, PAW process is employed on 2 mm thick Inconel 617 plates by varying the key process parameters, such as welding current and welding speed. Initially, bead on plate (BoP) experiments were conducted to determine the suitable range of welding parameters to weld the super alloy. Subsequently, butt welding of the plates was performed based on the results of BoP welding. Furthermore, a study was conducted to determine the influence of the welding process parameters on the microstructural and mechanical properties of the butt joints.

Selection and performance of AM superalloys for high-speed flight environments

In developing the Wire + Arc Additive Manufacturing (WAAM) process for the manufacture of components used in high-speed flight environments, a selection process for suitable alloys was devised. Using material properties from literature sources, creep-resistant alloys were down-selected based on the requirement for service in a high temperature, high stress environment and the need for an alloy suitable for manufacture using the WAAM process. Down-selected alloys, Inconel 718 (IN718), Rene 41 (RE41), Haynes 188 (H188) and Inconel 625 (IN625), were deposited by a plasma transferred arc WAAM process in an oxygen-controlled environment. Wall structures were built, and samples extracted for mechanical testing. The performance of as-deposited material was then compared against the wrought literature data. Tensile testing at room temperature revealed a performance mismatch, in comparison with wrought literature data, for precipitation strengthened IN718 & RE41; however, this performance mismatch was less significant for solution strengthened H188 and IN625. Results revealed that the AM material did not meet the wrought strength with performance varying depending on each alloy’s strengthening mechanism. Results illustrate the need for further processing to return the mechanical performance to wrought values.

Application of a modified hyperbolic sine creep rate equation to correlate uniaxial creep data vs. stress and temperature for creep resistant low chrome steel alloys

ABSTRACT Modified hyperbolic sine minimum creep rate equations were used to correlate uniaxial minimum creep strain rate data of 1/2Cr-1/2Mo-1/4 V and Grade 22 steel alloys and to correlate creep life data of Grade 22 steel when coupled with the Monkman-Grant equation. Hyperbolic sine equations were selected because of their physical basis in dislocation creep and numerical stability. Both equations provided very good fits to minimum strain rate data over a wide range of temperatures and stresses. Reasonable correlations of a large Grade 22 creep life data set were obtained with goodness of fit nearly equivalent to those obtained with the Larson-Miller and Wilshire equations, and with more conservative predictions of long-term creep strength. However, all these equations provided a poor fit to the entire data set when only short-term data (tr < 5,000 h) were correlated, and they predicted lower long-term creep rupture strengths vs. the full data set correlations.

Laser Powder Bed Fusion Additive Manufacturing of Fe3Al-1.5Ta Iron Aluminide with Strengthening Laves Phase

Advanced aluminides strengthened with incoherent Laves phase precipitates are promising lightweight and creep-resistant alternatives for high-alloy steels and superalloys for high-temperature critical components up to 750 °C service temperature. A significant issue with manufacturing these aluminides with conventional casting is the strong coarsening tendency of the Laves phase precipitates at elevated temperatures, leading to a significant strength reduction. In this context, the short lifetime of the melt pool in additive manufacturing and its fast solidification and cooling rates promise to consolidate these aluminides with homogeneously distributed fine Laves phase particles without coarsening. The main scientific objective of this work is to exploit the unique characteristics of the laser powder bed fusion (L-PBF) additive manufacturing (AM) process to print dense and crack-free bulk Fe3Al-1.5Ta samples containing uniformly distributed (Fe, Al)2Ta Laves phase precipitates. The Fe-25Al-2Ta (at.%) alloy was selected for this work since its creep resistance at 650 °C surpasses the one of the P92 martensitic–ferritic steel (one of the most creep-resistant alloys developed for steam turbine applications). Fundamentals on process–microstructure relationships governing the L-PBF-fabricated builds are provided by a detailed microstructural characterization using X-ray diffractometer (XRD) and ultra-high-resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and high-resolution electron backscatter diffraction (EBSD) detectors. Orientation imaging microscopy (OIM) and grain reference orientation deviation (GROD) maps were applied to measure texture and visualize substructures within the grains. The mechanism of voids formation, morphology, and volume fraction as a function of the input energy density was identified. The melting and solidification dynamics led to microstructures with large columnar grains, porosity, and periodic cracks during the printing process. Processing samples at the building temperatures below the brittle-to-ductile transition temperature, BDTT (750 °C), often caused severe macrocracking and delamination. Crack-free samples with densities higher than 99%, some approaching 99.5%, were fabricated from pre-alloyed gas-atomized powders with a combination of high laser power (250–300 W), slow-to-medium scanning speed (500–1000 mm/s), and 800 °C build plate preheating using a 67° rotation scanning strategy. The morphology of the pores in the volume of the samples indicated a relatively sharp transition from spherical geometry for scanning speeds up to 1000 mm/s to crack-like pores for higher values. The ultra-fast cooling during the L-PBF process suppressed D03 Fe3Al-ordering. The Fe3Al-1.5Ta builds were characterized by B2 FeAl-type order clusters dispersed within a disordered A2 α-(Fe, Al) matrix. Additionally, the (Fe, Al)2Ta Laves phase (C14–P63/mmc) was predominantly formed at the matrix phase grain boundaries and frequently dispersed within the grains. The quantitative EDX analysis of the matrix gave 77.6–77.9 at.% Fe, 21.4–21.7 at.% Al, and 0.6–0.8 at.% Ta, while the composition of the Laves phase was 66.3–67.8 at.% Fe, 8.7–9.8 at.% Al, and 22.4–24.9 at.% Ta, indicating that the Laves phase is considerably enriched in Ta with respect to the matrix. The L-PBF-fabricated alloys were characterized by coarse, columnar grains which grow epitaxially from the substrate, were several m in width, and extended across several layers along the building direction. The grains exhibited a relatively strong microtexture close to &lt;0 0 1&gt; with respect to the building direction. The L-PBF builds showed a bulk hardness value comparable to the as-cast and spark plasma-sintered counterparts. A negligible variation of the hardness across the build height was observed. Within the framework of this study, we demonstrated that the porosity and cracking issues could be resolved mainly by controlling the process parameters and preheating the build platform above the BDTT. Nevertheless, alloy modifications and/or post-manufacturing processing are required for microstructure refinement.

Crystal plasticity phase-field simulation of slip system anisotropy during creep of Co-Al-V monocrystal alloy under multidirectional strain

The preferable thermodynamic stability of L12 γ'-Co3(Al, V) phase and wide γ+γ' two-phase region endow the Co-Al-V alloy with great application potential. By introducing the digitized image of SEM morphology into phase-field simulation, utilizing the sublattice free energy model and the crystal plasticity strain model to simulate the anisotropic slip system, the rafting behaviors of the L12 γ'-Co3(Al, V) phase and the creep properties of Co-5Al-14V (at.%) alloy under tensile, compressive, shear, and monoclinic strains are studied. The partitioning ratio of element and orientation degree of γ' phase indicate that the uniaxial compressive strain improves the microstructural stability and the creep resistance at early creep stage. The creep resistance of alloy in state of equilibrium volume fraction of γ' phase is superior to that in the nonequilibrium volume fraction, and the creep resistance increases in order of tensile strain, compressive strain, and shear strain. Additionally, the dominant octahedral slip systems in fcc structure are (1¯1¯1)[101] under tensile strain, (1¯11)[01¯1] under compressive and 15° monoclinic strains, and (1¯1¯1)[1¯10] under 45° monoclinic strain. The hardening effect is prominent in γ matrix, and the high average critical resolved shear stress leads to the low creep strain. This study reveals the correlations between the slip system anisotropy and creep behaviors of Co-Al-V alloy under external strain, and also provides a method to combine the phase-field simulation with the experimental image for predicting the morphology evolution.

Substantial Improvement of High Temperature Strength of New-Generation Nano-Oxide-Strengthened Alloys by Addition of Metallic Yttrium.

Oxide-dispersion-strengthened (ODS) Fe-Al-Y2O3-based alloys (denoted as FeAlOY) containing 5 vol. % of nano-oxides have a potential to become top oxidation and creep-resistant alloys for applications at temperatures of 1100–1300 °C. Oxide dispersoids cause nearly perfect strengthening of grains; thus, grain boundaries with limited cohesive strength become the weak link in FeAlOY in this temperature range. One of the possibilities for significantly improving the strength of FeAlOY is alloying with appropriate elements and increasing the cohesive strength of grain boundaries. Nearly 20 metallic elements have been tested with the aim to increase cohesive strength in the frame of preliminary tests. A positive influence is revealed for Al, Cr, and Y, whereby the influence of Y is enormous (addition of 1% of metallic Y increases strength by a factor of 2), as it is presented in this paper.

Залежність структури ливарних сплавів системи Al-Ni-La від їх хімічного складу

The peculiarities of cast Al-Ni-La alloys structure formation depending on the content and ratio of the main components are analyzed in the work. It is shown, that so far the studied system has been considered mainly for the creation of amorphous materials. At the same time, Al-Ni and Al-La systems have phase diagrams that allow us to consider double and triple alloys of these systems to create promising creep-resistant alloys for casting. At the same time, the peculiarities of their structure formation in this context were not determined. Samples with different contents of nickel and lanthanum were prepared for research and analyzed how each of the elements, their number and ratio affect the formation of their structural-phase state. It is shown, that low nickel content of about 2 wt. % and lanthanum up to 5 wt. % eutectic is formed like thin almost monolithic intermetallic plates. As the number of components increases and, accordingly, the number of eutectics increases, the dispersion of its components increases. The analysis of the alloy structure dependence due to studied system on their chemical composition showed that, most likely, during the formation of the eutectic, Al11La3 particles, which may have the form of nanosized fibers, are formed first of all. It should be noted that at the eutectic content of lanthanum in the alloys no primary-formed Al11La3 particles were found. This may indicate that nickel shifts the eutectic concentration of lanthanum toward higher values. At the same time, at the hypoeutectic concentration of lanthanum and the hypereutectic concentration of nickel, some Al11La3 formations were outside the regions of the main eutectic with nickel aluminide. Such questions necessitate further studies of the aluminum angle of the triple state diagram of the Al-Ni-La system. Keywords: Al-Ni-La system, creep-resistant cast aluminum alloys, structure, eutectic.

Design and Characterization of Al-Cr-Nb-Ti-V-Zr High-Entropy Alloys for High-Temperature Applications

High-entropy alloys (HEAs) are a new class of metallic alloys without a principal component. These materials are attractive because of their unique structures and properties, including mechanical ones. Some of HEAs based on refractory metals are considered as advanced high-temperature materials. However, the development of new applicable compositions is complicated by poor understanding of relationships between the chemical and phase composition of HEAs and their effect on mechanical performance. Here we report the results of comprehensive studies of Al-Cr-Nb-Ti-V-Zr high-entropy alloys, particularly AlCrxNbTiVZry (х = 0.00, 0.25, 0.50, 1.00, 1.50 at y = 0 and y = 0.0, 0.25, 0.50, 1.00, 1.50 at x = 0). The strength and ductility of such alloys are shown to have a complex relationship with the composition and order of the parent B2 phase, and the amount and nature of secondary phases (C14 Laves phase and zirconium aluminides). Some of the investigated alloys demonstrate high specific strength at T ≤ 800°C. AlNbTiVZr0.25 alloy also has a stable microstructure and higher creep resistance at 600°C compared to existing creep-resistant alloys. Based on calculations of equilibrium and nonequilibrium phase diagrams by the CALPHAD method, we propose new Al-Cr-Nb-Ti-Zr alloy compositions with unique lamellar eutectic structure composed of the B2 and C14 Laves phases and with enhanced strength properties. The structure/property relationships and high-temperature deformation mechanisms of refractory HEAs with eutectic microstructure are analyzed.

ɤ-TiAl alloy: revisiting tensile creep deformation behaviour and creep life at 832 °C

ABSTRACT Creep deformation in single-phase ɤ-TiAl alloys manufactured using different processing techniques has been an extensively studied topic owing to the high specific strength and excellent creep properties of these alloys at temperatures between 760 and 1000°C. In addition, these lightweight and creep-resistant alloys are being presently considered as replacements to the comparatively heavier Ni-based superalloys for application in the low-pressure turbine blades of the next-generation gas turbine engines. However, there is limited information on the tensile creep deformation behaviour and creep life of ɤ-TiAl alloys at 832°C where these alloys have been reported not to exhibit steady-state creep. To this end, the present work revisits the work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Saha [1] and is aimed to develop an understanding of the tensile creep deformation behaviour at 832°C and the influence of creep activation energy on the creep life of wrought single-phase ɤ-TiAl alloy for stress levels of 69.4 and 103.4 MPa at 832°C using Monkman–Grant [2] approach.

A probabilistic creep model incorporating test condition, initial damage, and material property uncertainty

Uncertainty is prevalent in the creep resistance of alloys, where at elevated temperature and low pressure, rupture can range across logarithmic decades. In this study, a probabilistic continuum-damage-mechanics (CDM)-based model is derived to capture the uncertainty of creep resistance. To meet this objective, creep data for alloy 304 Stainless Steel is gathered. A constitutive model, “Sinh”, is calibrated deterministically to determine the statistical variability of the material properties. Three sources of uncertainty are injected into the model: test condition (stress and temperature), initial damage, and material properties. Probabilistic simulations are carried out by (a) calibrating probability distribution functions (pdfs) for each source of uncertainty (b) randomly sampling the pdfs using Monte Carlo methods and (c) executing simulations to replicate the uncertain creep behavior. A sensitivity analysis is performed to evaluate the relative effect of each source of uncertainty. In full probabilistic simulations, the cumulative uncertainty of creep behavior is evaluated. The probabilistic model accurately predicts the creep deformation and rupture of the available experiments. The probabilistic model is validated for interpolation but lacks extrapolation ability. Several future works are proposed to further improve the model.

A phenomenological model for predicting long-term high temperature creep life of materials from short-term high temperature creep test data

A phenomenological analysis for predicting the long-term creep life of high temperature materials at different temperatures using model parameters derived from short-term creep tests is presented. The model invokes Maxwell-Boltzmann temperature dependence, as rigorously developed in a recent analysis pertaining to the power law domain and a modified form of the Monkman-Grant hypothesis for isothermal conditions. In addition, the model provides, by pattern recognition, suitable weighting factors for the role of strain rate and temperature. The result is a material-dependent analysis which uses only short-term creep test data but is able to predict accurately both the short- and long-term creep behaviour of several complex creep-resistant alloys. This analysis is validated using reliable and accurate creep data taken from NIMS (National Institute of Materials Science, Japan) database pertaining to 10 industrial, high temperature alloys. The consistency or otherwise of the predictions is examined and the importance of the weighting factors in ensuring accurate predictions is emphasized.

Some aspects for increasing of heat-temperature strength of casting complex alloyed nickel-based alloys due to effect of redistribution of alloying elements between γ-solid solution and hardening γ′-phase

The positive effect of alloying elements on the thermal stability of the γ-matrix and the strengthening γ'-phase of casting nickel alloys, and consequently, on the increase in their heat-temperature strength is established. The alloying elements inhibit diffusion processes, thereby increasing the creep resistance of alloys at high temperatures and loads. It is found that the most indicative parameters of the phase composition of the test alloys are the alloying elements distribution coefficients between the γ- and γ'-phases. The basic principles of balanced alloying are formulated, on which the choice of the optimal chemical composition of heat-temperature nickel alloys is carried out.