ADVANCEMENTS IN AEROSPACE ALLOYS: NAVIGATING THE FUTURE OF AVIATION AND SPACE EXPLORATION

Nanoscale high-entropy alloy for electrocatalysis

Next-generation multicomponent SMAs: leveraging HEA empirical parameters

PurposeThis study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined.Design/methodology/approachMaterials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials.FindingsHEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA.Research limitations/implicationsThe AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages.Originality/valueIt is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.

High-temperature shape memory properties of Cu15Ni35Ti25Hf12.5Zr12.5 high-entropy alloy

Metallurgical aspects of high entropy alloys

Five high entropy alloys with shape memory effect or superelastic effect were prepared by cold crucible melting to understand the effect of their chemical composition on the transformation temperatures. The microstructure and phases of the alloys at room temperature were investigated by optical and scanning electron microscopy. The calorimetric study of these alloys is employed to analyze the reversible transformation from austenite to martensite and to determine the transformation temperatures of the five alloys. The paper presents the results of several published works relating the transformation temperatures of high entropy shape memory alloys (HE-SMA). An experimental database has been built up to understand the influence of the different alloying elements and their related concentrations on the transformation temperature Ms (Martensite Start) of the HE-SMAs. An equation is identified using the database to predict the transformation temperature Ms of a high entropy shape memory alloy as a function of its weighted chemical composition, which exhibits a metallurgical solutioned treatment (ST) state and a specific mixing entropy (ΔSmix/R) range.

A review on coating with high entropy alloy developed by laser energy based surfacing process

Amongst functional materials, shape-memory alloys occupy a special place. Discovered in the beginning of 1960th in XX century, these alloys attracted quite an attention because of the possibility to restore significant deformation amounts at certain stress–temperature conditions due to the martensitic diffusionless phase transformation involved in a process. It was possible to exploit not only so-called ‘shape-memory’ effect, but also superelasticity and high damping capacity. Over the years, more than 10 000 patents on shape-memory alloys were filed, appreciating not only the possibility to exploit energy transformation to ensure the response (feedback) at the change in independent thermodynamic parameters (temperature, stress, pressure, electric or magnetic field, etc.), but the significant work output as well. Applications ranged from different gadgets to automotive, aerospace industries, machine building, civil construction, etc. Unfortunately, the structural and functional fatigue restricted successful business application to medical sector with nitinol shape-memory alloy (different implants, stents, cardiovascular valves, etc.). Emerging high-entropy shape-memory alloys can be considered as a chance to overcome fatigue problems of existing industrial shape-memory alloys due to their specific structure that ensures superior resistance to irreversible plastic deformation.

As new generation of high-temperature shape memory alloys, high-entropy alloys (HEAs) have been attracted for strong solid-solution hardened alloys due to their severe lattice distortion and sluggish diffusion. TiPd is the one potential high-temperature shape memory alloys because of its high martensitic transformation temperature above 500 °C. As constituent elements, Zr expected solid-solution hardening, Pt expected increase of transformation temperature, Au expected keeping transformation temperature, and Co expected not to form harmful phase. By changing the alloy composition slightly, two HEAs and two medium entropy alloys (MEAs) were prepared. Only two MEAs, Ti45Zr5Pd25Pt20Au5, and Ti45Zr5Pd25Pt20Co5 had the martensitic transformation. The perfect recovery was obtained in Ti45Zr5Pd25Pt20Co5 during the repeated thermal cyclic test, training, under 200 MPa. On the other hand, the small irrecoverable strain was remained in Ti45Zr5Pd25Pt20Au5 during the training under 150 MPa because of the small solid-solution hardening effect. It indicates that Ti45Zr5Pd25Pt20Co5 is the one possible HT-SMA working between 342 and 450 °C.

The integration of machine learning (ML) into alloy design has revolutionized the discovery and optimization of advanced materials by enabling high-throughput, data-driven methodologies. This review systematically examines recent advancements in ML applications across diverse alloy systems, including steels, aluminum alloys, magnesium alloys, nickel-based superalloys, high-entropy alloys (HEAs), shape memory alloys, and metallic glasses. We categorize ML approaches into supervised, unsupervised, and reinforcement learning paradigms, detailing their specific implementations for property prediction, phase stability analysis, and composition optimization. Advanced techniques, such as inverse design frameworks and physics-informed ML models, have demonstrated substantial improvements in predictive accuracy and interpretability by integrating domain knowledge with data-driven approaches. The review further explores the synergy between ML and traditional computational methods, including CALPHAD-based thermodynamic modeling and density functional theory (DFT), enhancing the reliability of property predictions. We highlight case studies where ML-driven strategies have successfully accelerated alloy discovery, optimized mechanical properties, and identified novel compositions with tailored performance metrics. Additionally, we address key challenges in ML-driven alloy design, including data scarcity, feature selection, model interpretability, and the necessity for standardized benchmarking datasets. By providing a comprehensive evaluation of current methodologies and emerging trends, this review underscores the transformative role of ML in advancing next-generation alloy design and manufacturing, ultimately enabling the rapid development of high-performance materials for aerospace, energy, biomedical, and structural applications.

Molecular dynamics simulation and machine learning-based analysis for predicting tensile properties of high-entropy FeNiCrCoCu alloys

High entropy or multi principal element alloys are a promising and relatively young concept for designing alloys. The idea of creating alloys without a single main alloying element opens up a wide space for possible new alloy compositions. High entropy alloys based on refractory metals such as W, Mo, Ta or Nb are of interest for future high temperature applications e.g., in the aerospace or chemical industry. However, producing refractory metal high entropy alloys by conventional metallurgical methods remains challenging. For this reason, the feasibility of laser-based additive manufacturing of the refractory metal high entropy alloy W20Mo20Ta20Nb20V20 by laser powder bed fusion (PBF-LB/M) is investigated in the present work. In-situ alloy formation from mixtures of easily available elemental powders is employed to avoid an expensive atomization of pre-alloyed powder. It is shown that PBF-LB/M of W20Mo20Ta20Nb20V20 is in general possible and that a complete fusion of the powder mixture without a significant number of undissolved particles is achievable by in-situ alloy formation during PBF-LB/M when selecting favorable process parameter combinations. The relative density of the samples with a dimension of 6 × 6 × 6 mm3 reaches, in dependence of the PBF-LB/M parameter set, 99.8%. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements confirm the presence of a single bcc-phase. Scanning electron microscopy (SEM) images show a dendritic and/or cellular microstructure that can, to some extent, be controlled by the PBF-LB/M parameters.

Enhancing the oxidation resistance of nanocrystalline high-entropy AlCuCrFeMn alloys by the addition of tungsten

Additive manufacturing (AM) technologies have gained considerable attention in recent years as an innovative method to produce high entropy alloy (HEA) components. The unique and excellent mechanical and environmental properties of HEAs can be used in various demanding applications, such as the aerospace and automotive industries. This review paper aims to inspect the status and prospects of research and development related to the production of HEAs by AM technologies. Several AM processes can be used to fabricate HEA components, mainly powder bed fusion (PBF), direct energy deposition (DED), material extrusion (ME), and binder jetting (BJ). PBF technologies, such as selective laser melting (SLM) and electron beam melting (EBM), have been widely used to produce HEA components with good dimensional accuracy and surface finish. DED techniques, such as blown powder deposition (BPD) and wire arc AM (WAAM), that have high deposition rates can be used to produce large, custom-made parts with relatively reduced surface finish quality. BJ and ME techniques can be used to produce green bodies that require subsequent sintering to obtain adequate density. The use of AM to produce HEA components provides the ability to make complex shapes and create composite materials with reinforced particles. However, the microstructure and mechanical properties of AM-produced HEAs can be significantly affected by the processing parameters and post-processing heat treatment, but overall, AM technology appears to be a promising approach for producing advanced HEA components with unique properties. This paper reviews the various technologies and associated aspects of AM for HEAs. The concluding remarks highlight the critical effect of the printing parameters in relation to the complex synthesis mechanism of HEA elements that is required to obtain adequate properties. In addition, the importance of using feedstock material in the form of mix elemental powder or wires rather than pre-alloyed substance is also emphasized in order that HEA components can be produced by AM processes at an affordable cost.

Shape memory alloys (SMAs) are ones which can return to their original shape under impact of temperature or external magnetic field. The SMAs are capable of many applications in the fields of biomedical, aerospace, microelectronics, automation, for examples, orthodontics, stents, bone anchors, automatic valves, heat sensors, nanotweezers, robots... Recently, researchers have discovered the shape memory effect (SME) on high entropy alloys (HEAs). The combination of superior properties of SMAs and HEAs (high strength, heat resistance, low diffusion coefficient...) would bring useful practical applications in practice. In this paper, we will present an overview of the research situation of SMAs and our initial results obtained on Ni-Ti based alloys of Ni-Ti, Ni-Ti-Zr-Cu-Cr, Ni-Ti-Zr-Cu-Co, Ni-Ti-Zr-Cu-Nb, and Ni-Ti-Zr-Cu-Hf prepared by melt-spinning method.