Multi-principal Element Alloys Research Articles

A roadmap from the bond strength to the grain-boundary energies and macro strength of metals

Correlating the bond strength with the macro strength of metals is crucial for understanding mechanical properties and designing multi-principal-element alloys (MPEAs). Motivated by the role of grain boundaries in the strength of metals, we introduce a predictive model to determine the grain-boundary energies and strength of metals from the cohesive energy and atomic radius. This scheme originates from the d-band characteristics and broken-bond spirit of tight-binding models, and demonstrates that the repulsive/attractive effects play different roles in the variation of bond strength for different metals. Importantly, our framework not only applies to both pure metals and MPEAs, but also unravels the distinction of the bond strength caused by elemental compositions, lattice structures, high-entropy, and amorphous effects. These findings build a physical picture across bond strength, grain-boundary energies and strength of metals by using easily accessible material properties and provide a robust method for the design of high-strength alloys.

Visualizing high entropy alloy spaces: methods and best practices

Multi-Principal Element Alloys (MPEAs) have emerged as an exciting area of research in materials science in the 2020s, owing to the vast potential for discovering alloys with unique and tailored properties enabled by the combinations of elements.

Rapid co-reduction synthesis of ultrafine multi-principal element alloy nanocatalysts for efficient hydrogen evolution

A rapid co-reduction strategy for the synthesis of ultrafine and composition-tunable multi-principal element alloy catalysts is proposed. This method necessitates only a 10-minute reaction time at 180°C and featuers straightforward...

Interstitial oxygen solutes promote atomic-scale heterogeneities to achieve superior irradiation tolerance in body-centered cubic multi-principal element alloys

Interstitial oxygen solutes promote atomic-scale heterogeneities to achieve superior irradiation tolerance in body-centered cubic multi-principal element alloys

Enhancing the mechanical properties of TiZr-based multi-principal element alloys via leveraging multiple short-range orders: an atomic-scale study

Enhancing the mechanical properties of TiZr-based multi-principal element alloys via leveraging multiple short-range orders: an atomic-scale study

Quantum and complex-valued hybrid networks for multi-principal element alloys phase prediction.

This study introduces a hybrid network model for phase classification, integrating quantum networks and complex-valued neural networks. This architecture uses elemental composition as its only input, eliminating complex feature engineering. Parameterized quantum networks handle sparse elemental data and convert data from real to complex domains, increasing information dimensionality. Complex-valued neural networks process data in the complex domain, significantly reducing information loss during transitions. The experimental results show that the hybrid model achieves a phase classification accuracy of 94.93%, outperforming the best machine learning model by 2.27% and the quantum model by 8.67%. Precision, recall, and F1-score are also excellent at 0.9494, 0.9493, and 0.9500, respectively. Additional tests on phase transitions in alloys confirm the model's robust generalization, identifying transition thresholds at 0.46 and 0.88, closely matching the 0.45 and 0.88 reported in related studies.

Hydrogen Induced Superhydrophilicity in an Amorphous CrFeNi-Based Multi-Principal Element Alloy Thin Film

Hydrogen Induced Superhydrophilicity in an Amorphous CrFeNi-Based Multi-Principal Element Alloy Thin Film

Surface passivation on precipitated Ti-containing multi-principal element alloy subject to metal aging

Surface passivation on precipitated Ti-containing multi-principal element alloy subject to metal aging

Al and Ti co-addition enhancing the corrosion resistance in Co-free Cr1.3Fe2Ni2 multi-principal element alloy

Al and Ti co-addition enhancing the corrosion resistance in Co-free Cr1.3Fe2Ni2 multi-principal element alloy

Superior oxidation behavior, good electrical conductivity, and thermophysical properties of FeCr1.2Ni1.5Al multi-principal element alloys

Superior oxidation behavior, good electrical conductivity, and thermophysical properties of FeCr1.2Ni1.5Al multi-principal element alloys

Dual-Nano Composite Design with Grain Boundary Segregation for Enhanced Strength and Plasticity in CoCrNi-CuZr Thin Films.

Enhancing both strength and plasticity simultaneously in nanostructured materials remains a significant challenge. While grain refinement is effective in increasing strength, it typically leads to reduced plasticity due to localized strain. In this study, we propose a novel design strategy featuring a dual-nano composite structure with grain boundary segregation to enhance the deformation stability of nanostructured materials. This strategy is demonstrated using a CoCrNi-CuZr multiprincipal element alloy film, which shows a dual-nano composite structure with high-density nanotwins and crystalline-amorphous nanocomposite, along with elemental segregation at the columnar grain boundaries. Our strategy achieves homogeneous plastic deformation in a (CoCrNi)91(CuZr)9 thin film, an 18% increase in strength compared to nanocrystalline CoCrNi, and a 67% increase compared to amorphous CuZr thin films. These results provide valuable insights into designing high-strength, ductile alloys through the engineering of dual-nano composite structures.

Bimetallic CuNi Nanoparticle Formation: Solution Combustion Synthesis and Molecular Dynamic Approaches.

Nanomaterials are vital in catalysis, sensing, energy storage, and biomedicine and now incorporate multiprincipal element materials to meet evolving technological demands. However, achieving a uniform distribution of multiple elements in these nanomaterials poses significant challenges. In this study, various Cu-Ni compositions were used as a model system to investigate the formation of bimetallic nanoparticles by employing computer simulation molecular dynamics methods and comparing the results with observations from solution-combustion-synthesized materials of the same compositions. The findings reveal the successful synthesis of 12-18 nm bimetallic Cu-Ni nanoparticles with high phase homogeneity, alongside phase-segregated nanoparticles predicted by molecular dynamics simulations. Based on the comparison of the experimental and computational data, a possible scenario for phase segregation during the synthesis was proposed. It includes clustering of the atoms of the same type in an initial solution or the stage of gel formation and further developing segregation during the combustion/cooling stage. The research concludes that early synthesis stages, including particle preformation, significantly influence the phase homogeneity of multiprincipal element alloys. This study contributes to understanding nanomaterial formation, offering insights for improved alloy synthesis and enhanced functionalities in advanced applications.

Experimentally Validated and Empirically Compared Machine Learning Approach for Predicting Yield Strength of Additively Manufactured Multi-Principal Element Alloys from Co–Cr–Fe–Mn–Ni System

Experimentally Validated and Empirically Compared Machine Learning Approach for Predicting Yield Strength of Additively Manufactured Multi-Principal Element Alloys from Co–Cr–Fe–Mn–Ni System

A Complex Concentrated Alloy with Record-High Strength-Toughness at 77 K.

High strength and large ductility, leading to a high material toughness (area under the stress-strain curve), are desirable for alloys used in cryogenic applications. Assisted by domain-knowledge-informed machine learning, here a complex concentrated Fe35Co29Ni24Al10Ta2 alloy is designed, which uses L12 coherent nanoprecipitates in a high volume fraction (≈65 ± 3 vol.%) in a face-centered-cubic (FCC) solid solution matrix that undergoes FCC-to-body-centered-cubic (BCC) phase transformation upon tensile straining. Unlike FCC-to-BCT phase transformation involving brittle carbon-enriched martensite, the BCC martensite in this alloy does not cause brittleness at 77 K. The Fe35Co29Ni24Al10Ta2 multi-principal element alloy achieves a high yield strength ≈1.4GPa, a high work hardening rate >4GPa, an ultimate tensile strength ≈2.25GPa, and a large uniform elongation ≈45%, leading to record-high material toughness compared with previous cryogenic alloys such as 316L series stainless steels and recent high-entropy alloys. The nanoprecipitates with nanoscale spacing (≈7.5nm), apart from serving as dislocation obstacles for strengthening and dislocation sources for sustainable ductility, also undergo deformation twinning. Taken together, these mechanisms are found to be highly effective in strengthening and strain hardening upon tensile straining at liquid nitrogen temperature. These findings demonstrate how to effectively integrate strengthening mechanisms to synergize superior mechanical properties in special-purpose alloys.

The spontaneous passivation of multi principal element alloys II: The effect of Mn in the CoCrFeNiMn family

The spontaneous passivation of multi principal element alloys II: The effect of Mn in the CoCrFeNiMn family

Crack propagation of CoCrFeNiTi-based multiprincipal element alloys formed by laser powder bed fusion in electrolytic hydrogen and high-pressure hydrogen gas environments

Crack propagation of CoCrFeNiTi-based multiprincipal element alloys formed by laser powder bed fusion in electrolytic hydrogen and high-pressure hydrogen gas environments

Hf-induced strengthening and lattice distortion in Hf NbTaTiV refractory multi-principal element alloys

Hf-induced strengthening and lattice distortion in Hf NbTaTiV refractory multi-principal element alloys

A survey of energies from pure metals to multi-principal element alloys

In materials science, a wide range of properties of materials are governed by various types of energies, including thermal, physicochemical, structural, and mechanical energies. In 2005, Dr. Frans Spaepen used crystalline face-centered cubic (fcc) copper as an example to discuss a variety of phenomena that are associated with energies. Inspired by his pioneering work, we broaden our analysis to include a selection of representative pure metals with fcc, hexagonal close-packed (hcp), and body-centered cubic (bcc) structures. Additionally, we extend our comparison to energies between pure metals and equiatomic binary, ternary, and multi-principal element alloys [sometimes also known as high-entropy alloys (HEAs)]. Through an extensive collection of data and calculations, we compile energy tables that provide a comprehensive view of how structure and alloying influence the energy profiles of these metals and alloys. We highlight the significant impact of constituent elements on the energies of alloys compared to pure metals and reveal a notable disparity in mechanical energies among materials in fcc-, hcp- and bcc-structured metals and alloys. Furthermore, we discuss the energy relationships, the implications for structural transformations and potential applications, providing insights into the broader context of these energy variations.

Self-Healing Properties of High Entropy Alloys:Insights from Element Resolved Electrochemistry

Multi-principal element alloys such as the high entropy alloy family are promising for diverse applications. Navigating the large number of possible element combinations however represents a serious obstacle for the optimization of alloy composition. Progress will require a clear understanding of what each elemental component will add to the overall behavior of the alloy. Corrosion resistance is a particularly interesting case in that the usual techniques of electrochemistry measure only the rate of electron transfer. Element resolved electrochemistry (or AESEC, atomic emission specroelectrochemistry) provides information by (1) allowing us to measure directly and quantitatively the contribution of each element to the electrochemical behavior [1], and (2) allowing us to measure directly the open circuit corrosion rate. These measurement are invaluable for the investigation of complex alloys as it gives us specific information on the role of each alloying component. In this work we will discuss the phenomenon of repassivation - the ability of a material to reform the passive film following damage to the film. At open circuit, the reaction is driven by the oxidizing strength of the environment. This is an essential property that will often determine the corrosion resistance of the material under a variety of conditions. However, it is difficult to assess by conventional electrochemical methods as no electrochemical current is measured. AESEC provides a direct measurement of the repassivation rate as well as information on which elements are enriching on the surface [2]. In addition to the open circuit corrosion measurements, the chemistry of the alloying elements may be investigated over a wide range of potential using element resolved polarization curves. A series of alloys were prepared in-house based on the Cantor alloy composition, CoCrFeMnNi. The rate of repassivation in a sulfuric acid electrolyte was determined following the removal of the passive film by electrochemical means. Firstly, we will present results as a function of Cr content and Mn content representing the alloying components that are well known to either enhance (Cr) or degrade (Mn) the formation of the passive film. The we will present results for a series of alloys replacing Mn with an alternative element, including Mo, V, Ti, Al, W and Cu.The extent to which each alternative element enhances or degrades the spontaneous passivation was investigated quantitatively. Insight into the mechanism of passivation (or degradation) was revealed by determining the extent of selective dissolution or surface enrichment during spontaneous reaction with the electrolyte and as a function of potential during conventional linear polarization experiments. This family of elements covers a wide range of electrochemical behavior and consequently we anticipate that each element will affect the repassivation in a unique manner. In this way, this work may serve as a compendium of mechanisms that may be generalized to other elements showing similar properties.1) “Atomic emission spectroelectrochemistry: Real time rate measurements of dissolution, corrosion and passivation”, K Ogle, Corrosion, 75 (2019)1398-1419. (Open access)2) “Spontaneous passivation of the CoCrFeMnNi high entropy alloy in sulfuric acid solution: the effects of alloyed nitrogen and dissolved oxygen”, X Li, P Zhou, H Feng, Z Jiang, H Li, K Ogle, Corrosion Science, (2022)110016.

Enhancing fatigue resistance of Cr-Mn-Fe-Co-Ni multi-principal element alloys by varying stacking fault energy and sigma (σ)-phase assisted grain-size reduction

This study investigates two key aspects of the low cycle fatigue (LCF) behavior of alloys from the Cr-Mn-Fe-Co-Ni system at room temperature: (1) the influence of stacking fault energy (SFE) in single-phase face-centered cubic (FCC) alloys and (2) a grain size reduction triggered by the precipitation of a small amount of σ-phase. The first effect is investigated using model alloys (Cr26Mn20Fe20Co20Ni14 and Cr14Mn20Fe20Co20Ni26 in at.%, grain size: ∼60 µm), which have distinct SFEs at room temperature. A reduction in SFE from 69 to 23 mJ/m2 results in a 10 to 20 % increase in tensile/compressive peak stresses, i.e., cyclic strength, across all examined strain amplitudes (±0.3 %, ±0.5 %, and ±0.7 %) while maintaining comparable fatigue lives. Despite its higher cyclic strength, the low-SFE alloy exhibits delayed, and less evolved dislocation substructures than the other alloy. In both single-phase alloys, fatigue cracks originated from the surface reliefs, surface-exposed coherent annealing twin boundaries, and occasionally from high-angle grain boundaries. However, the crack propagation rate was slower in the low-SFE alloy, contributing to its superior fatigue resistance. By aging the low-SFE Cr26Mn20Fe20Co20Ni14 alloy differently, we could induce the precipitation of ∼5 % σ-phase during recrystallization, which strongly reduced the FCC grain size to ∼5 µm. With this microstructure, the cyclic strength increased by 50–65 % and remained more stable during fatigue testing while maintaining a comparable life. The σ-precipitates were found to deflect and arrest fatigue cracks, while extensive deformation twinning around cracks complements slip activity and reduces crack propagation rate. Overall, the σ-phase-assisted grain size reduction is 3 to 5 times more effective in improving cyclic strength than SFE reduction.