Journal articles: 'Superalloys High entropy alloys'

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Zhang, Hang, Yizhen Zhao, Sheng Huang, Shuo Zhu, Fu Wang, and Dichen Li. "Manufacturing and Analysis of High-Performance Refractory High-Entropy Alloy via Selective Laser Melting (SLM)." Materials 12, no. 5 (March 1, 2019): 720. http://dx.doi.org/10.3390/ma12050720.

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Refractory high-entropy alloys (HEAs) have excellent mechanical properties, which could make them the substitutes of some superalloys. However, the high melting point of refractory HEAs leads to processing problems when using traditional processing techniques. In this study, a single BCC solid solution of NbMoTaW alloy was formed by selective laser melting (SLM) with a linear energy density of up to 2.83 J/mm. The composition distribution was analyzed, and the element with a lower melting point and lower density showed a negative deviation (no more than 5%) of the molar ratio in the formed alloy. The HEA shows an excellent microstructure, microhardness, and corrosion resistance performance compared with traditional superalloys, making it a new substitute metal with great application prospects in aerospace and energy fields.

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Manzoni, Anna, Sebastian Haas, Haneen Daoud, Uwe Glatzel, Christiane Förster, and Nelia Wanderka. "Tensile Behavior and Evolution of the Phases in the Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex/High Entropy Alloy." Entropy 20, no. 9 (August 29, 2018): 646. http://dx.doi.org/10.3390/e20090646.

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Compositionally complex alloys, or high entropy alloys, are good candidates for applications at higher temperatures in gas turbines. After their introduction, the equiatomic Al17Co17Cr17Cu17Fe17Ni17 (at.%) served as a starting material and a long optimization road finally led to the recently optimized Al10Co25Cr8Fe15Ni36Ti6 (at.%) alloy, which shows promising mechanical properties. Investigations of the as-cast state and after different heat treatments focus on the evolution of the microstructure and provide an overview of some mechanical properties. The dendritic solidification provides two phases in the dendritic cores and two different ones in the interdendritic regions. Three of the four phases remain after heat treatments. Homogenization and subsequent annealing produce a γ-γ’ based microstructure, similar to Ni-based superalloys. The γ phase is Co-Cr-Fe rich and the γ’ phase is Al-Ni-Ti rich. The understanding of the mechanical behavior of the investigated alloy is supported and enhanced by the study of the different phases and their nanohardness measurements. The observations are compared with mechanical and microstructural data from commercial Ni-based superalloys, Co-based alloys, and Co-Ni-based alloys at the desired application temperature of ~800 °C.

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Liu, Feng, Zexin Wang, Zi Wang, Zijun Qin, Zihang Li, Liang Jiang, Lan Huang, Liming Tan, and Yong Liu. "Evaluating yield strength of Ni-based superalloys via high throughput experiment and machine learning." Journal of Micromechanics and Molecular Physics 05, no. 04 (December 2020): 2050015. http://dx.doi.org/10.1142/s2424913020500150.

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Yield strength (YS) is a key factor during design and application of Ni-based superalloys with complex compositions, hence it is of great significance to evaluate the YS prior to manufacturing. In this work, alloy diffusion-multiple technology was employed as a high-throughput way to yield the hardness dataset. Based on the composition and other descriptors, Pearson correlation coefficients, stability selection and feature importance were used to select the efficient feature variables. Thereafter, six different machine learning models were applied to predict the YS. Finally, the individual and interaction effect of Co and Mo could be effectively detected by the Gaussian process regression (GPR) model. The optimum composition of Ni-based superalloys with the largest YS at room temperature was determined using the trained GPR model and genetic algorithm. This method can be extended to predict the YS in other multicomponent alloys, such as Ti alloys, Co-based alloys, and high entropy alloys.

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Wang, Z., Y. Huang, J. Wang, and C. T. Liu. "Design of high entropy alloys based on the experience from commercial superalloys." Philosophical Magazine Letters 95, no. 1 (January 2, 2015): 1–6. http://dx.doi.org/10.1080/09500839.2014.987841.

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Cobbinah, Prince Valentine, Rivel Armil Nzeukou, Omoyemi Temitope Onawale, and Wallace Rwisayi Matizamhuka. "Laser Powder Bed Fusion of Potential Superalloys: A Review." Metals 11, no. 1 (December 30, 2020): 58. http://dx.doi.org/10.3390/met11010058.

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The laser powder bed fusion (LPBF) is an additive manufacturing technology involving a gradual build-on of layers to form a complete component according to a computer-aided design. The LPBF process boasts of manufacturing value-added parts with higher accuracy and complex geometries for the transport, aviation, energy, and biomedical industries. TiAl-based alloys and high-entropy alloys (HEAs) are two materials envisaged as potential replacements of nickel-based superalloys for high temperature structural applications. The success of these materials hinge on optimization and implementation of tailored microstructures through controlled processing and appropriate alloy manipulations that can promote and stabilize new microstructures. Therefore, it is important to understand the LPBF technique, and its associated microstructure-mechanical property relationships. This paper discusses the metallurgical sintering processes of LPBF, the effects of process parameters on densification, microstructures, and mechanical properties of LPBFed TiAl-based alloys and HEAs. This paper also, presents updates and future studies recommendations on the LPBFed TiAl-based alloys and HEAs.

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Liu, Tian-Wei, Tong Li, and Lan-Hong Dai. "Near-Equiatomic μ Phase in Self-Sharpening Tungsten-Based High-Entropy Alloys." Metals 12, no. 7 (July 1, 2022): 1130. http://dx.doi.org/10.3390/met12071130.

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The topologically close-packed (TCP) μ phase is usually known as an undesirable precipitation in highly alloyed Ni-base superalloys and steels. However, the ultrastrong μ phase with micron/nano-scale distribution plays a key role in driving the emergence of self-sharpening in our recently developed WMoFeNi high-entropy alloy (HEA). Herein, a detailed study is carried out to understand the substructure and atomic occupation of the μ phase by scanning electron microscope (SEM) and aberration-corrected transmission electron microscope (ACTEM). The Fe/Ni and W/Mo element pairs are equivalent in the μ-phase structure. Moreover, the elements in μ phase exhibit a near-equiatomic ratio, and the μ phase can grow during annealing at 1150 °C. (0001)μ and (11¯02)μ. Twins are the main substructures of the μ phase, and their atomic configurations and twinning mechanisms are investigated. The geometrical structural analysis of μ phase possesses a great significance for the design of self-sharpening HEAs.

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Tseng, Ko-Kai, Chien-Chang Juan, Shuen Tso, Hsuan-Chu Chen, Che-Wei Tsai, and Jien-Wei Yeh. "Effects of Mo, Nb, Ta, Ti, and Zr on Mechanical Properties of Equiatomic Hf-Mo-Nb-Ta-Ti-Zr Alloys." Entropy 21, no. 1 (December 25, 2018): 15. http://dx.doi.org/10.3390/e21010015.

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Nowadays refractory high-entropy alloys (RHEAs) are regarded as great candidates for the replacement of superalloys at high temperature. To design a RHEA, one must understand the pros and cons of every refractory element. However, the elemental effect on mechanical properties remains unclear. In this study, the subtraction method was applied on equiatomic HfMoNbTaTiZr alloys to discover the role of each element, and, thus, HfMoNbTaTiZr, HfNbTaTiZr, HfMoTaTiZr, HfMoNbTiZr, HfMoNbTaZr, and HfMoNbTaTi were fabricated and analyzed. The microstructure and mechanical properties of each alloy at the as-cast state were examined. The solid solution phase formation rule and the solution strengthening effect are also discussed. Finally, the mechanism of how Mo, Nb, Ta, Ti, and Zr affect the HfMoNbTaTiZr alloys was established after comparing the properties of these alloys.

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Naser-Zoshki, Hamed, Ali-Reza Kiani-Rashid, and Jalil Vahdati-Khaki. "Non-equiatomic W₁₀Mo₂₇Cr₂₁Ti₂₂Al₂₀ high-entropy alloy produced by mechanical alloying and spark plasma sintering: Phase evolution and mechanical properties." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 236, no. 4 (January 12, 2022): 695–703. http://dx.doi.org/10.1177/14644207211051038.

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In this work, non-equiatomic W10Mo27Cr21Ti22Al20 refractory high-entropy alloy (RHEA) was produced using mechanical alloying followed by spark plasma sintering. The phase formation, microstructure, and compressive mechanical properties of the alloy were studied. During mechanical alloying, a Body-centered cubic (BCC) solid solution phase with a particle size of less than 1 µm was obtained after 18 h ball milling. The microstructure of the sintered sample exhibits three distinct phases consisting of two solid solution phases BCC1 and BCC2 as well as fine TiCxOy precipitates distributed in them. The volume fractions of each phase were about 79%, 8%, and 13%, respectively. The sintered W10Mo27Cr21Ti22Al20 showed yield strengths of 2465, 1506, 405, and 290 MPa at room temperature 600, 1000, and 1200°C, respectively, which are about twice that of the same refractory high-entropy alloy produced by vacuum arc melting. At 1000 and 1200°C, the strength after yielding gradually increased to 970 and 718 MPa at a compressive strain of 60%. The studied refractory high-entropy alloy can have good potential in high-temperature applications due to its high specific strength at elevated temperatures compared to conventional Ni-based superalloys and most as-reported refractory high-entropy alloys.

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Tsao, Te-Kang, An-Chou Yeh, and Hideyuki Murakami. "The Microstructure Stability of Precipitation Strengthened Medium to High Entropy Superalloys." Metallurgical and Materials Transactions A 48, no. 5 (March 8, 2017): 2435–42. http://dx.doi.org/10.1007/s11661-017-4037-6.

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Haas, Sebastian, Anna M. Manzoni, Fabian Krieg, and Uwe Glatzel. "Microstructure and Mechanical Properties of Precipitate Strengthened High Entropy Alloy Al10Co25Cr8Fe15Ni36Ti6 with Additions of Hafnium and Molybdenum." Entropy 21, no. 2 (February 12, 2019): 169. http://dx.doi.org/10.3390/e21020169.

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High entropy or compositionally complex alloys provide opportunities for optimization towards new high-temperature materials. Improvements in the equiatomic alloy Al17Co17Cr17Cu17Fe17Ni17 (at.%) led to the base alloy for this work with the chemical composition Al10Co25Cr8Fe15Ni36Ti6 (at.%). Characterization of the beneficial particle-strengthened microstructure by scanning electron microscopy (SEM) and observation of good mechanical properties at elevated temperatures arose the need of accomplishing further optimization steps. For this purpose, the refractory metals hafnium and molybdenum were added in small amounts (0.5 and 1.0 at.% respectively) because of their well-known positive effects on mechanical properties of Ni-based superalloys. By correlation of microstructural examinations using SEM with tensile tests in the temperature range of room temperature up to 900 °C, conclusions could be drawn for further optimization steps.

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Ghadami, Farzin, Mohammad Amin Davoudabadi, and Soheil Ghadami. "Cyclic Oxidation Properties of the Nanocrystalline AlCrFeCoNi High-Entropy Alloy Coatings Applied by the Atmospheric Plasma Spraying Technique." Coatings 12, no. 3 (March 10, 2022): 372. http://dx.doi.org/10.3390/coatings12030372.

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Microcrystalline and nanocrystalline AlCrFeCoNi high-entropy alloy (HEA) coatings were applied on Inconel 718 superalloy using the atmospheric plasma spraying (APS) process. The high-temperature oxidation behavior of the microcrystalline and nanocrystalline AlCrFeCoNi HEA-coated superalloy was examined at 1100 °C under the air atmosphere for 50 cycles under cyclic heating and cooling (1 h for each cycle). The oxidation kinetics of both nanocrystalline- and microcrystalline-coated superalloys were accordingly analyzed by weight change measurements. We noted that the uncoated and coated samples followed the parabolic rate law of the oxidation. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the oxidized coated and uncoated samples. In the HEA-coated superalloy, Fe, Ni, Co and Al were oxidized in the inter-splat region, whereas the splats, which consisted mainly of Ni and Cr, remained unoxidized. Due to the formation of compact and adhesive thin NiO, CoO oxides and spinels together with the Al2O3 oxide scale on the surface of the coating during oxidation, the developed nanocrystalline HEA coating showed better oxidation resistance compared with the microcrystalline HEA coating.

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12

Whitfield, Tamsin E., Howard J. Stone, C. Neil Jones, and Nicholas G. Jones. "Microstructural Degradation of the AlMo0.5NbTa0.5TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures." Entropy 23, no. 1 (January 8, 2021): 80. http://dx.doi.org/10.3390/e23010080.

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Refractory metal high-entropy superalloys (RSA), which possess a nanoscale microstructure of B2 and bcc phases, have been developed to offer high temperature capabilities beyond conventional Ni-based alloys. Despite showing a number of excellent attributes, to date there has been little consideration of their microstructural stability, which is an essential feature of any material employed in high temperature service. Here, the stability of the exemplar RSA AlMo0.5NbTa0.5TiZr is studied following 1000 h exposures at 1200, 1000 and 800 °C. Crucially, the initial nanoscale cuboidal B2 + bcc microstructure was found to be unstable following the thermal exposures. Extensive intragranular precipitation of a hexagonal Al-Zr-rich intermetallic occurred at all temperatures and, where present, the bcc and B2 phases had coarsened and changed morphology. This microstructural evolution will concomitantly change both the mechanical and environmental properties and is likely to be detrimental to the in-service performance of the alloy.

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Whitfield, Tamsin E., Howard J. Stone, C. Neil Jones, and Nicholas G. Jones. "Microstructural Degradation of the AlMo0.5NbTa0.5TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures." Entropy 23, no. 1 (January 8, 2021): 80. http://dx.doi.org/10.3390/e23010080.

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Refractory metal high-entropy superalloys (RSA), which possess a nanoscale microstructure of B2 and bcc phases, have been developed to offer high temperature capabilities beyond conventional Ni-based alloys. Despite showing a number of excellent attributes, to date there has been little consideration of their microstructural stability, which is an essential feature of any material employed in high temperature service. Here, the stability of the exemplar RSA AlMo0.5NbTa0.5TiZr is studied following 1000 h exposures at 1200, 1000 and 800 °C. Crucially, the initial nanoscale cuboidal B2 + bcc microstructure was found to be unstable following the thermal exposures. Extensive intragranular precipitation of a hexagonal Al-Zr-rich intermetallic occurred at all temperatures and, where present, the bcc and B2 phases had coarsened and changed morphology. This microstructural evolution will concomitantly change both the mechanical and environmental properties and is likely to be detrimental to the in-service performance of the alloy.

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14

Srikanth, Muthe, A. Raja Annamalai, A. Muthuchamy, and Chun-Ping Jen. "A Review of the Latest Developments in the Field of Refractory High-Entropy Alloys." Crystals 11, no. 6 (May 28, 2021): 612. http://dx.doi.org/10.3390/cryst11060612.

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This review paper provides insight into current developments in refractory high-entropy alloys (RHEAs) based on previous and currently available literature. High-temperature strength, high-temperature oxidation resistance, and corrosion resistance properties make RHEAs unique and stand out from other materials. RHEAs mainly contain refractory elements like W, Ta, Mo, Zr, Hf, V, and Nb (each in the 5–35 at% range), and some low melting elements like Al and Cr at less than 5 at%, which were already developed and in use for the past two decades. These alloys show promise in replacing Ni-based superalloys. In this paper, various manufacturing processes like casting, powder metallurgy, metal forming, thin-film, and coating, as well as the effect of different alloying elements on the microstructure, phase formation, mechanical properties and strengthening mechanism, oxidation resistance, and corrosion resistance, of RHEAs are reviewed.

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Wang, Qing, Zhen Li, Shujie Pang, Xiaona Li, Chuang Dong, and Peter Liaw. "Coherent Precipitation and Strengthening in Compositionally Complex Alloys: A Review." Entropy 20, no. 11 (November 15, 2018): 878. http://dx.doi.org/10.3390/e20110878.

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High-performance conventional engineering materials (including Al alloys, Mg alloys, Cu alloys, stainless steels, Ni superalloys, etc.) and newly-developed high entropy alloys are all compositionally-complex alloys (CCAs). In these CCA systems, the second-phase particles are generally precipitated in their solid-solution matrix, in which the precipitates are diverse and can result in different strengthening effects. The present work aims at generalizing the precipitation behavior and precipitation strengthening in CCAs comprehensively. First of all, the morphology evolution of second-phase particles and precipitation strengthening mechanisms are introduced. Then, the precipitation behaviors in diverse CCA systems are illustrated, especially the coherent precipitation. The relationship between the particle morphology and strengthening effectiveness is discussed. It is addressed that the challenge in the future is to design the stable coherent microstructure in different solid-solution matrices, which will be the most effective approach for the enhancement of alloy strength.

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Andrews, Ross N., Joseph Serio, Govindarajan Muralidharan, and Jan Ilavsky. "Anin situUSAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy." Journal of Applied Crystallography 50, no. 3 (May 30, 2017): 734–40. http://dx.doi.org/10.1107/s1600576717006446.

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Intermetallic γ′ precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure duringin situheat treatment. Analysis of PSDs from USAXS–SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoidinga prioridefinition of a functional form of the PSD. However, strong low-qscattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian–MaxEnt analysis methods to data exhibiting structure factor effects and low-qpower law slopes and demonstrates their use in anin situstudy of precipitate size evolution during heat treatment of a model Ni–Al–Si alloy.

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Yang, Jun-Jie, Chia-Ming Kuo, Po-Ting Lin, Hung-Chih Liu, Cheng-Yao Huang, Hung-Wei Yen, and Che-Wei Tsai. "Improvement in oxidation behavior of Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy superalloys by minor Nb addition." Journal of Alloys and Compounds 825 (June 2020): 153983. http://dx.doi.org/10.1016/j.jallcom.2020.153983.

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Biermair, Florian, and Gerald Ressel. "The effect of homogenization on microstructure and hardness of a large-scale high-aluminum Al4.4Co26Cr18Fe18Ni26Ti5.5 Compositionally Complex Alloy cast." International Journal of Materials Research 112, no. 8 (June 29, 2021): 642–51. http://dx.doi.org/10.1515/ijmr-2021-8219.

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Abstract As any largescale cast material, specific Compositionally Complex Alloys or High Entropy Superalloys contain segregations, leading to unideal, inhomogeneous properties. This work presents the effects of a homogenization heat treatment at 1 150°C for 6 h of a large-scale cast Al4.4Co26Cr18Fe18Ni26Ti5.5 alloy. In order to reveal these effects, homogenized specimens were analyzed and compared to the as-cast state with regard to chemical homogeneity as well as the homogeneity of elemental solution by means of scanning electron microscopy, energy dispersive X-ray spectroscopy as well as X-ray diffraction and hardness measurements. Despite the increased Al content, intermetallic phases and segregations, observable in the as-cast state, dissolve during homogenization. Improved, but not full homogeneity of elemental distribution after annealing can be determined. The improved state of solution and homogeneity agrees with the increasing lattice parameter from 3.572 Å to 3.594 Å and the decreasing hardness from 320.3 HV10 to 245.2 HV10 during homogenization.

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Ching, Wai-Yim, Saro San, Caizhi Zhou, and Ridwan Sakidja. "Ab Initio Simulation of Structure and Properties in Ni-Based Superalloys: Haynes282 and Inconel740." Materials 16, no. 2 (January 16, 2023): 887. http://dx.doi.org/10.3390/ma16020887.

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The electronic structure, interatomic bonding, and mechanical properties of two supercell models of Ni-based superalloys are calculated using ab initio density functional theory methods. The alloys, Haynes282 and Inconel740, are face-centered cubic lattices with 864 atoms and eleven elements. These multi-component alloys have very complex electronic structure, bonding and partial-charge distributions depending on the composition and strength of the local bonding environment. We employ the novel concept of total bond order density (TBOD) and its partial components (PBOD) to ascertain the internal cohesion that controls the intricate balance between the propensity of metallic bonding between Ni, Cr and Co, and the strong bonds with C and Al. We find Inconel740 has slightly stronger mechanical properties than Haynes282. Both Inconel740 and Haynes282 show ductile natures based on Poisson’s ratio. Poisson’s ratio shows marginal correlation with the TBOD. Comparison with more conventional high entropy alloys with equal components are discussed.

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20

Suryanarayana, Challapalli. "Mechanical Alloying: A Novel Technique to Synthesize Advanced Materials." Research 2019 (May 30, 2019): 1–17. http://dx.doi.org/10.34133/2019/4219812.

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Mechanical alloying is a solid-state powder processing technique that involves repeated cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed about 50 years ago to produce oxide-dispersion-strengthened Ni- and Fe-based superalloys for aerospace and high temperature applications, it is now recognized as an important technique to synthesize metastable and advanced materials with a high potential for widespread applications. The metastable materials produced include supersaturated solid solutions, intermediate phases, quasicrystalline phases, amorphous alloys, and high-entropy alloys. Additionally, nanocrystalline phases have been produced in virtually every alloy system. Because of the fineness of the powders, their consolidation to full density without any porosity being present is a challenging problem. Several novel methods have been developed to overcome this issue. Powder contamination during milling and subsequent consolidation constitutes another issue; this can be resolved, though expensive. A number of applications have been developed for these novel materials. This review article presents an overview of the process of mechanical alloying, mechanism of grain refinement to nanometer levels, and preparation of materials such as nanocomposites and metallic glasses. The application of mechanical alloying to synthesize some advanced materials such as pure metals and alloys, hydrogen storage materials, and energy materials is described. The article concludes with an outlook on future prospects of this technique.

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Lee, Kangjin, Yunjong Jung, Junhee Han, Sung Hwan Hong, Ki Buem Kim, Peter K. Liaw, Chanho Lee, and Gian Song. "Development of Precipitation-Strengthened Al0.8NbTiVM (M = Co, Ni) Light-Weight Refractory High-Entropy Alloys." Materials 14, no. 8 (April 20, 2021): 2085. http://dx.doi.org/10.3390/ma14082085.

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Single-phase solid-solution refractory high-entropy alloys (RHEAs) have been receiving significant attention due to their excellent mechanical properties and phase stability at elevated temperatures. Recently, many studies have been reported regarding the precipitation-enhanced alloy design strategy to further improve the mechanical properties of RHEAs at elevated temperatures. In this study, we attempted to develop precipitation-hardened light-weight RHEAs via addition of Ni or Co into Al0.8NbTiV HEA. The added elements were selected due to their smaller atomic radius and larger mixing enthalpy, which is known to stimulate the formation of precipitates. The addition of the Ni or Co leads to the formation of the sigma precipitates with homogeneous distribution. The formation and homogeneous distribution of sigma particles plays a critical role in improvement of yield strength. Furthermore, the Al0.8NbTiVM0.2 (M = Co, Ni) HEAs show excellent specific yield strength compared to single-phase AlNbTiV and NbTiVZr RHEA alloys and conventional Ni-based superalloy (Inconel 718) at elevated temperatures.

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Whitfield, T. E., E. J. Pickering, K. A. Christofidou, C. N. Jones, H. J. Stone, and N. G. Jones. "Elucidating the microstructural development of refractory metal high entropy superalloys via the Ti–Ta–Zr constituent system." Journal of Alloys and Compounds 818 (March 2020): 152935. http://dx.doi.org/10.1016/j.jallcom.2019.152935.

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Whitfield, Tamsin E., George J. Wise, Ed J. Pickering, Howard J. Stone, and Nicholas G. Jones. "An Investigation of the Miscibility Gap Controlling Phase Formation in Refractory Metal High Entropy Superalloys via the Ti-Nb-Zr Constituent System." Metals 11, no. 8 (August 5, 2021): 1244. http://dx.doi.org/10.3390/met11081244.

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Refractory metal high entropy superalloys (RSAs) have been heralded as potential new high temperature structural materials. They have nanoscale cuboidal bcc+B2 microstructures that are thought to form on quenching through a spinodal decomposition process driven by the Ta-Zr or Nb-Zr miscibility gaps, followed by ordering of one of the bcc phases. However, it is difficult to isolate the role of different elemental interactions within compositionally complex RSAs. Therefore, in this work the microstructures produced by the Nb-Zr miscibility gap within the compositionally simpler Ti-Nb-Zr constituent system were investigated. A systematic series of alloys with compositions of Ti5NbxZr95−x (x = 25–85 at.%) was studied following quenching from solution heat treatment and long duration thermal exposures at 1000, 900 and 700 °C for 1000 h. During exposures at 900 °C and above the alloys resided in a single bcc phase field. At 700 °C, alloys with 40–75 at.% Nb resided within a three phase bcc + bcc + hcp phase field and a large misfit, 4.7–5%, was present between the two bcc phases. Evidence of nanoscale cuboidal microstructures was not observed, even in slow cooled samples. Whilst it was not possible to conclusively determine whether a spinodal decomposition occurs within this ternary system, these insights suggest that Nb-Zr interactions may not play a significant role in the formation of the nanoscale cuboidal RSA microstructures during cooling.

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Zarkevich, Nikolai A., Timothy M. Smith, Eli N. Baum, and John W. Lawson. "Compositional Glass: A State with Inherent Chemical Disorder, Exemplified by Ti-rich Ni3(Al,Ti)1 D024 Phase." Crystals 12, no. 8 (July 28, 2022): 1049. http://dx.doi.org/10.3390/cryst12081049.

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A compositional glass is a state with an unavoidable disorder in chemical compositions on each site, characterized by frustration and freezing of the compositional degrees of freedom at low temperature. From this state a full atomic long-range order is unachievable by a reasonable thermodynamic treatment. There is a similarity between a spin glass (a magnetic state with disorder in spin orientations) and a compositional glass (with disorder in site occupations by chemical elements): both have frustrated ground states and a frozen disorder at low temperatures T < Tf (here Tf is called the freezing temperature). While it is possible to perform a ground-state search in a compositional glass, the resulting set of the fully ordered structures does not adequately represent the real solid with an inherent atomic disorder. Compositional glasses constitute a class of materials, which is insufficiently understood, but is of high industrial importance. Some of the phases in the precipitated alloys (including steels, high-entropy alloys, and superalloys) might be compositional glasses, and their better understanding would facilitate materials design. Due to their strength at high operating temperatures, superalloys are used in combustion engines and particularly in jet turbine engines. Precipitation strengthening of nickel superalloys is an area of active research. Local phase transformations inside Ni3Al-based precipitates are of particular interest due to their impact on creep strength. In the Ni3(Al1−xTix)1 ternary system, the competing phases are Ni3Al-type L12 (γʹ) and Ni3Ti-type D024 (η), while D019 (χ) is higher in energy. These three phases differ by the stacking of atomic layers: locally, the last two look like the internal and external stacking faults in L12. We compute enthalpies of disordered and ordered Ni3(Al1−xTix)1 ternary structures, examine phase stability, investigate the ground states and competing structures, and predict that the Ti-rich Ni3(Al1−xTix)1 D024 phase is a compositional glass with the atomic disorder on the Al/Ti sublattice. To resolve apparent contradictions among the previous experiments and to confirm our prediction, we perform X-ray diffraction and scanning electron microscopy analysis of the cast Ni3(Ti0.917Al0.083)1 sample. Our measurements appear to confirm the ab initio computed results. Our results elucidate properties of compositional glasses and provide a better understanding of precipitation strengthening mechanisms in Ni superalloys.

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Chen, Shiyao, Qin Li, Jing Zhong, Fangzhou Xing, and Lijun Zhang. "On diffusion behaviors in face centered cubic phase of Al-Co-Cr-Fe-Ni-Ti high-entropy superalloys." Journal of Alloys and Compounds 791 (June 2019): 255–64. http://dx.doi.org/10.1016/j.jallcom.2019.03.286.

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Katz-Demyanetz, Alexander, Vladimir V. Popov, Aleksey Kovalevsky, Daniel Safranchik, and Andrey Koptyug. "Powder-bed additive manufacturing for aerospace application: Techniques, metallic and metal/ceramic composite materials and trends." Manufacturing Review 6 (2019): 5. http://dx.doi.org/10.1051/mfreview/2019003.

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The current paper is devoted to classification of powder-bed additive manufacturing (PB-AM) techniques and description of specific features, advantages and limitation of different PB-AM techniques in aerospace applications. The common principle of “powder-bed” means that the used feedstock material is a powder, which forms “bed-like” platform of homogeneous layer that is fused according to cross-section of the manufactured object. After that, a new powder layer is distributed with the same thickness and the “printing” process continues. This approach is used in selective laser sintering/melting process, electron beam melting, and binder jetting printing. Additionally, relevant issues related to powder raw materials (metals, ceramics, multi-material composites, etc.) and their impact on the properties of as-manufactured components are discussed. Special attention is paid to discussion on additive manufacturing (AM) of aerospace critical parts made of Titanium alloys, Nickel-based superalloys, metal matrix composites (MMCs), ceramic matrix composites (CMCs) and high entropy alloys. Additional discussion is related to the quality control of the PB-AM materials, and to the prospects of new approaches in material development for PB-AM aiming at aerospace applications.

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Shafiee, Ahad, Mahmoud Nili-Ahmadabadi, Hyoung Seop Kim, and Mohammad Jahazi. "Development and Microstructural Characterization of a New Wrought High Entropy Superalloy." Metals and Materials International 26, no. 5 (July 23, 2019): 591–602. http://dx.doi.org/10.1007/s12540-019-00360-w.

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Suksamran, Amnart, Nawarat Worauaychai, Nattaya Tosangthum, Thanyaporn Yodkaew, Rungtip Krataitong, Pongsak Wila, and Ruangdaj Tongsri. "Effect of Aluminum Addition on Al_xCoFeMnNiZn Multi-Component Production." Key Engineering Materials 751 (August 2017): 53–59. http://dx.doi.org/10.4028/www.scientific.net/kem.751.53.

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Five multi-component alloy (MCA) formulations of CoFeMnNiZn (MCA01), Al0.5CoFeMnNiZn (MCA02), Al1.0CoFeMnNiZn (MCA03), Co5Fe5Mn30Ni20Zn40 (MCA04) and Al8.4Co4.6Fe4.6Mn27Ni18.4Zn37 (MCA05) were prepared by mechanical alloying and melting process (MAM). Five-component alloys of MCA01-MCA05 were designed using empirical formulae for high entropy alloys. Phase formation and microstructure were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that MCA01 was partially melted by MAM process. However, MCA02-MCA05 could be melted and cast by MAM process. The microstructures of as-cast MCA02 and MCA03 showed dendritic solidification. Nevertheless, the as-cast MCA04 showed microstructure similar to that of Ni-based superalloy, i.e., the as-cast MCA04 consisted of γ matrix and γ′ phase. Moreover, egg type core shell structure was found in the interdendritic regions of the MCA05 alloy. In addition, the Al-added MCA02 and MCA03 alloys showed crystal structures of FCC1, FCC2 and BCC. MCA04 alloy demonstrated crystal structure of FCC whereas MCA05 alloy had crystal structures of FCC and Primitive Cubic.

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29

Sridar, Soumya, Noah Sargent, Xin Wang, Michael A. Klecka, and Wei Xiong. "Determination of Location-Specific Solidification Cracking Susceptibility for a Mixed Dissimilar Alloy Processed by Wire-Arc Additive Manufacturing." Metals 12, no. 2 (February 5, 2022): 284. http://dx.doi.org/10.3390/met12020284.

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Solidification cracking is a major obstacle when joining dissimilar alloys using additive manufacturing. In this work, location-specific solidification cracking susceptibility has been investigated using an integrated computational materials engineering (ICME) approach for a graded alloy formed by mixing P91 steel and Inconel 740H superalloy. An alloy mixture of 26 wt.% P91 and 74 wt.% Inconel 740H, with high configurational and total entropy, was fabricated using wire arc additive manufacturing. Microstructure characterization revealed intergranular solidification cracks in the FCC matrix, which increased in length along with the enrichment of Nb (~27 to 56 wt.%) and Cu (~87 wt.%) in the middle and top regions. DICTRA simulations to model location-specific solidification cracking susceptibility showed that the top region with the highest cooling rate (270 K/s) has the highest solidification cracking susceptibility in comparison with the middle and bottom regions. This is in good agreement with the experimentally observed varying crack length. From Scheil simulations, it was deduced that enrichment of Nb and Cu affected the solidification range as high as ~77%, in comparison with the matrix composition. The overall solidification cracking susceptibility and freezing range was highest for the 26 wt.% P91 alloy amongst the mixed compositions between P91 steel and 740H superalloy, proving that solidification characteristics play a major role in alloy design for additive manufacturing.

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Hardwick, Liam, Pat Rodgers, Ed Pickering, and Russell Goodall. "Development of a Novel Ni-Based Multi-principal Element Alloy Filler Metal, Using an Alternative Melting Point Depressant." Metallurgical and Materials Transactions A 52, no. 6 (April 3, 2021): 2534–48. http://dx.doi.org/10.1007/s11661-021-06246-0.

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AbstractBrazing is a crucial joining technology in industries where nickel-superalloy components must be joined. Nickel-based brazing filler metals are extensively employed, possessing excellent mechanical properties, corrosion resistance, and retained strength at elevated temperatures. To function as a filler metal, the alloy melting point must be reduced to below that of the materials being joined, but the addition of melting point depressants (MPDs) such as boron, silicon, and phosphorus can, however, lead to the formation of brittle intermetallics, potentially compromising the joint performance. In the present work, a novel multi-principal element brazing alloy (in the style of a high entropy alloy), utilizing Ge as an alternative MPD along with a reduced B addition, is investigated. The design process considered binary phase diagrams and predictions based on Thermo-Calc software and empirical thermodynamic parameters. The alloy was used to vacuum braze nickel-superalloy Inconel-718, and microstructural and mechanical investigations are reported. The maximum shear strength achieved was 297 MPa with a brazing temperature of 1100 °C and 60-minute hold time, with isothermal solidification completed. Shear strength was only slightly reduced with increased joint width. Assessments are made of the ability to accurately predict properties of multi-principle element alloys using Thermo-Calc software and empirical thermodynamic parameters.

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Ren, H. S., H. L. Feng, X. Y. Ren, S. J. Pang, Y. Y. Cheng, and H. P. Xiong. "Joining of TiAl-based alloy and a Ni-based superalloy with a NiCoFeCuSiB high entropy filler metal." Welding in the World 66, no. 3 (January 5, 2022): 557–65. http://dx.doi.org/10.1007/s40194-021-01245-6.

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32

Detrois, Martin, Paul D. Jablonski, Stoichko Antonov, Shilei Li, Yang Ren, Sammy Tin, and Jeffrey A. Hawk. "Design and thermomechanical properties of a γʹ precipitate-strengthened Ni-based superalloy with high entropy γ matrix." Journal of Alloys and Compounds 792 (July 2019): 550–60. http://dx.doi.org/10.1016/j.jallcom.2019.04.054.

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33

Shahbazkhan, Armita, Hamed Sabet, and Mehrdad Abbasi. "Investigation of bonding strength and hot corrosion behavior of NiCoCrAlSi high entropy alloy applied on IN-738 superalloy by SPS method." Journal of Alloys and Compounds 911 (August 2022): 164997. http://dx.doi.org/10.1016/j.jallcom.2022.164997.

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34

Kong, Taeyeong, Byungchul Kang, Ho Jin Ryu, and Soon Hyung Hong. "Microstructures and enhanced mechanical properties of an oxide dispersion-strengthened Ni-rich high entropy superalloy fabricated by a powder metallurgical process." Journal of Alloys and Compounds 839 (October 2020): 155724. http://dx.doi.org/10.1016/j.jallcom.2020.155724.

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35

Miracle, Daniel B., Ming-Hung Tsai, Oleg N. Senkov, Vishal Soni, and Rajarshi Banerjee. "Refractory high entropy superalloys (RSAs)." Scripta Materialia 187 (October 2020): 445–52. http://dx.doi.org/10.1016/j.scriptamat.2020.06.048.

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36

Li, Peng, Haotian Sun, Shuai Wang, Yueqing Xia, Honggang Dong, Guodong Wen, and Hao Zhang. "Diffusion bonding of AlCoCrFeNi2.1 eutectic high entropy alloy to GH4169 superalloy." Materials Science and Engineering: A 793 (August 2020): 139843. http://dx.doi.org/10.1016/j.msea.2020.139843.

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37

Glatzel, Uwe, Felix Schleifer, Christian Gadelmeier, Fabian Krieg, Moritz Müller, Mike Mosbacher, and Rainer Völkl. "Quantification of Solid Solution Strengthening and Internal Stresses through Creep Testing of Ni-Containing Single Crystals at 980 °C." Metals 11, no. 7 (July 16, 2021): 1130. http://dx.doi.org/10.3390/met11071130.

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Various alloy compositions were cast as single crystals in a Bridgman vacuum induction furnace and creep tested at 980 °C: pure Ni, the equiatomic alloys CoCrNi and CrMnFeCoNi (Cantor alloy), single-phase fcc (Ni) solid solution alloys (with the composition of the matrix-phase of CMSX-3 and CMSX-4), and two-phase Ni-based superalloys CMSX-3 and CMSX-4. Due to the single-crystal state, grain size effects, grain boundary sliding, and grain boundary diffusion can be excluded. The results identify two major strengthening mechanisms: solid solution strengthening and other mechanisms summarized as precipitation hardening. Configurational entropy does not increase creep strength: The Cantor alloy, with the highest configurational entropy of all alloys tested, shows a weak and similar creep strength at 980 °C in comparison to pure Ni with zero configurational entropy. The element Re is a very effective strengthener, both in single-phase fcc (Ni) solid solution alloys as well as in two-phase superalloys. Quantitative estimations of different strengthening mechanisms: internal back stress, misfit stresses, Orowan bowing, and γ′-phase cutting (in the case of two-phase superalloys) are presented. Finite element simulations allow estimating the influence of solid solution strengthening of the matrix on the creep behavior of the two-phase superalloys.

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38

Lam, Tu-Ngoc, You-Shiun Chou, Yao-Jen Chang, Tsung-Ruei Sui, An-Chou Yeh, Stefanus Harjo, Soo Yeol Lee, Jayant Jain, Bo-Hong Lai, and E.-Wen Huang. "Comparing Cyclic Tension-Compression Effects on CoCrFeMnNi High-Entropy Alloy and Ni-Based Superalloy." Crystals 9, no. 8 (August 13, 2019): 420. http://dx.doi.org/10.3390/cryst9080420.

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An equal-molar CoCrFeMnNi, face-centered-cubic (fcc) high-entropy alloy (HEA) and a nickel-based superalloy are studied using in situ neutron diffraction experiments. With continuous measurements, the evolution of diffraction peaks is collected for microscopic lattice strain analyses. Cyclic hardening and softening are found in both metallic systems. However, as obtained from the diffraction-peak-width evolution, the underneath deformation mechanisms are quite different. The CoCrFeMnNi HEA exhibits distinct lattice strain and microstructure responses under tension-compression cyclic loadings.

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39

Chen, Yung-Ta, Yao-Jen Chang, Hideyuki Murakami, Stéphane Gorsse, and An-Chou Yeh. "Designing high entropy superalloys for elevated temperature application." Scripta Materialia 187 (October 2020): 177–82. http://dx.doi.org/10.1016/j.scriptamat.2020.06.002.

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40

Tsao, Te-Kang, An-Chou Yeh, Chen-Ming Kuo, and Hideyuki Murakami. "High Temperature Oxidation and Corrosion Properties of High Entropy Superalloys." Entropy 18, no. 2 (February 22, 2016): 62. http://dx.doi.org/10.3390/e18020062.

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41

Bhadeshia, H. K. D. H. "High entropy alloys." Materials Science and Technology 31, no. 10 (June 18, 2015): 1139–41. http://dx.doi.org/10.1179/0267083615z.000000000969.

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42

Kozak, Roksolana, and Walter Steurer. "High-entropy alloys." Acta Crystallographica Section A Foundations of Crystallography 69, a1 (August 25, 2013): s497. http://dx.doi.org/10.1107/s0108767313095718.

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43

George, Easo P., Dierk Raabe, and Robert O. Ritchie. "High-entropy alloys." Nature Reviews Materials 4, no. 8 (June 18, 2019): 515–34. http://dx.doi.org/10.1038/s41578-019-0121-4.

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44

Zhang, Yong, Jien-Wei Yeh, Jian F. Sun, Jun P. Lin, and Ke-Fu Yao. "High-Entropy Alloys." Advances in Materials Science and Engineering 2015 (2015): 1. http://dx.doi.org/10.1155/2015/781303.

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45

Sokkalingam, R., B. Pravallika, K. Sivaprasad, V. Muthupandi, and K. G. Prashanth. "Dissimilar welding of high-entropy alloy to Inconel 718 superalloy for structural applications." Journal of Materials Research 37, no. 1 (October 22, 2021): 272–83. http://dx.doi.org/10.1557/s43578-021-00352-w.

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AbstractHigh-entropy alloy, a new generation material, exhibits superior structural properties. For high-temperature applications, where dissimilar materials are in demand, HEAs may be joined with commercially available structural materials to improve their performance-life ratio. In this connection, a dissimilar joint was fabricated by gas tungsten arc welding between Al0.1CoCrFeNi-HEA and Inconel 718. The columnar dendritic grains are growing epitaxially at the Al0.1CoCrFeNi-HEA/weld metal interface, where their compositions are matching. While the composition misfit at the weld metal/Inconel 718 interface, reveals the non-epitaxial mode of solidification. In addition, the fusion zone exhibits the porosity and micro-segregation of NbC and Laves phases. The joint shows a joint efficiency of ~ 88%, where the strength is observed to be 644 MPa with 21% ductility. The results demonstrate the applicability of GTAW in fabricating the dissimilar weld joints between HEA and Inconel 718 for structural applications. Graphic abstract

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46

Wu, Yifeng, and Douglas L. Irving. "Prediction of chemical ordering in refractory high-entropy superalloys." Applied Physics Letters 119, no. 11 (September 13, 2021): 111901. http://dx.doi.org/10.1063/5.0059453.

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Raabe, Dierk, Cemal Cem Tasan, Hauke Springer, and Michael Bausch. "From High-Entropy Alloys to High-Entropy Steels." steel research international 86, no. 10 (July 21, 2015): 1127–38. http://dx.doi.org/10.1002/srin.201500133.

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48

Gao, Michael, and Junwei Qiao. "High-Entropy Alloys (HEAs)." Metals 8, no. 2 (February 6, 2018): 108. http://dx.doi.org/10.3390/met8020108.

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Liu, Xiongjun, Rajarshi Banerjee, Levente Vitos, and Yandong Wang. "Metastable high entropy alloys." Applied Physics Letters 120, no. 12 (March 21, 2022): 120401. http://dx.doi.org/10.1063/5.0091351.

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50

Feuerbacher, Michael, Markus Heidelmann, and Carsten Thomas. "Hexagonal High-entropy Alloys." Materials Research Letters 3, no. 1 (August 21, 2014): 1–6. http://dx.doi.org/10.1080/21663831.2014.951493.

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Journal articles on the topic 'Superalloys High entropy alloys'

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