Corrosion Resistance Of High Entropy Alloys Research Articles

Corrosion resistance of FeCrMnxAlCu high-entropy alloys in 0.5M H2SO4 solution

In this study, FeCrMnxAlCu high-entropy alloys with varying Mn contents (x = 2.0, 1.5, 1.0, 0.5, and 0) were prepared using a vacuum arc melting furnace. The phase structure and microstructure of the alloys before and after corrosion were characterized via X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion resistance of the alloys in a 0.5 M H2SO4 solution was comprehensively evaluated through potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests, white light interferometry, and X-ray photoelectron spectroscopy. Microstructural characterization results revealed that the FeCrMnxAlCu high-entropy alloys exhibited mixed FCC and BCC phase structures and featured typical dendritic and interdendritic regions. Corrosion tests indicated that as the Mn content decreased, the corrosion resistance of the high-entropy alloys improved, and the corrosion type transitioned from dendritic to interdendritic. Among these alloys, the FeCrAlCu high-entropy alloy exhibited the highest corrosion resistance, with the highest positive corrosion potential (Ecorr = −0.11 V), the lowest corrosion current density (Icorr = 1.02 × 10−5 A∙cm2), minimal corrosion depth, and the lowest corrosion rate (0.1592 mm/y). After corrosion, a composite oxide protective film was formed on the alloy surface, effectively hindering further penetration of the H2SO4 solution and exhibiting excellent corrosion resistance.

Machine learning-assisted prediction and interpretation of electrochemical corrosion behavior in high-entropy alloys

In this study, machine learning (ML) models were successfully employed to predict the short-term electrochemical corrosion behavior of high-entropy alloys (HEAs) based on their chemical compositions. Considering the vast compositional space of HEAs, which restricts the development of corrosion-resistant HEAs, and the lack of non-destructive methods to qualitatively assess their corrosion resistance, this work represents a significant advancement in the field. The “three-step” method was applied to select the optimal feature set from 38 features, and six ML regression models were trained and compared. The eXtreme Gradient Boosting (XGBoost) and Gradient Boosting Decision Tree (GBDT) algorithms demonstrated the highest predictive accuracy (R2 = 81.02 % and 84.64 %, respectively) among the six algorithms. The model’s robust generalization capabilities were confirmed through validation on an additional dataset. Moreover, the interpretability of the model was enhanced by employing two analysis methods, which revealed that pH as an environmental factor, electronegativity difference and average electronegativity as empirical parameters, and the concentrations of Cr and Cu as compositional parameters have the most significant impact on the corrosion resistance of HEAs. The proposed methodology and framework have the potential to optimize alloy composition, facilitating the design and development of new corrosion-resistant HEAs.

Effect of annealing treatment on the mechanical properties and corrosion behaviour of Co40Cr20Ni30Al4.5Ti5Mo0.5 high-entropy alloy

Cast high-entropy alloys are frequently found to have large internal tensions, compositional segregation, and shrinkage defects, which can directly prevent them from performing as intended. Proper heat treatment can modify the internal structure of an alloy and enhance its overall performance. This study describes a new nonequiatomic proportional cast Co40Cr20Ni30Al4.5Ti5Mo0.5 high-entropy alloy prepared by a vacuum induction melting technique. The impacts of different annealing temperatures (700, 800, 900, and 1000 °C) on the microstructure evolution mechanism, mechanical properties and corrosion behaviour of the alloy are systematically examined. The results show that the heat treatment can successfully improve the overall mechanical properties and corrosion resistance of high-entropy alloys while suppressing casting defects. The alloy exhibits the best overall mechanical properties after annealing at 700 °C, with a yield strength of 923 MPa and a tensile strength of 1090 MPa. After annealing at a temperature of 800 °C, the alloy demonstrates excellent corrosion resistance, characterized by a low passivation current density, a large passivation range, and a high corrosion potential. Specifically, ipass is measured to be 4.59 × 10−7A/cm2, and Ecorr is −319 mV. Furthermore, the maximum Cr2O3 oxide content in the alloy passivation film formed at 800 °C contributes to the passivation film stability.

Achieving ultrafine lamellar structure and exceptional electrochemical properties of Fe35Mn27Ni28Co5Cr5 high-entropy alloy through severe cold rolling process

This research provides an insight into the effect of ultrafine lamellar microstructures on the electrochemical behavior of Fe35Mn27Ni28Co5Cr5 high-entropy alloys (HEAs) in a 0.5 M H2SO4 solution. Following the severe cold rolling (SCR) process at a reduction rate of 90 %, the Fe35Mn27Ni28Co5Cr5 alloy exhibited a predominantly lamellar microstructure aligned along the rolling direction, leading to variations in grain size and subsequent differences in electrochemical behaviors. The potentiodynamic polarization (PDP) plots and electrochemical impedance spectroscopy (EIS) measurements confirmed that the influence of heavy cold rolling on corrosion resistance was mainly attributed to grain refinement and residual stress. The corrosion resistance of HEAs was ameliorated as a result of increased rolling deformation. The 90 % cold-rolled specimen showed excellent comprehensive corrosion resistance, for which the Ecorr and icorr values were found to be −0.278 V and 329 µA/cm2. Consequently, the development of ultrafine lamellar structures provides better conditions for forming passive films with higher protection behavior compared with their other counterparts. It could be due to the improved surface conditions for the development of oxide films resulting from higher homogeneity. The present work will provide new opportunities for tailoring the electrochemical characteristics of HEAs with strong commercial viability.

The Effect of Heat Treatment and Tungsten Content on the Structure, Phase Composition, and Corrosion Resistance of High-Entropy Alloys of the Fe–Cr–Ni–Mo–W System

The Effect of Heat Treatment and Tungsten Content on the Structure, Phase Composition, and Corrosion Resistance of High-Entropy Alloys of the Fe–Cr–Ni–Mo–W System

Machine learning accelerated discovery of corrosion-resistant high-entropy alloys

Corrosion has a wide impact on society, causing catastrophic damage to structurally engineered components. An emerging class of corrosion-resistant materials are high-entropy alloys. However, high-entropy alloys live in high-dimensional composition and configuration space, making materials designs via experimental trial-and-error or brute-force ab initio calculations almost impossible. Here we develop a physics-informed machine-learning framework to identify corrosion-resistant high-entropy alloys. Three metrics are used to evaluate the corrosion resistance, including single-phase formability, surface energy and the compactness of oxide films formed on an alloy surface evaluated by Pilling–Bedworth ratios. We used random forest models to predict the single-phase formability, trained on an experimental dataset. Machine learning inter-atomic potentials were employed to calculate surface energies and Pilling–Bedworth ratios, which are trained on first-principles data fast sampled using embedded atom models. A combination of random forest models and high-fidelity machine learning potentials represents the first of its kind to relate chemical compositions to corrosion resistance of high-entropy alloys, paving the way for automatic design of materials with superior corrosion protection. This framework was demonstrated on AlCrFeCoNi high-entropy alloys and we identified composition regions with high corrosion resistance from a wide range of compositions. Machine learning predicted lattice constants and surface energies are consistent with values by first-principles calculations. The predicted single-phase formability and corrosion-resistant compositions of AlCrFeCoNi agree well with experiments. This framework provides a computationally efficient approach to navigate high-dimensional composition space of high-entropy alloys. It is general in its application and applicable to other complex materials, enabling high-throughput screening of material candidates and potentially accelerating the iteration of integrated computational materials engineering.

Corrosion resistance and mechanism of high‐entropy alloys: A review

AbstractEnvironmental corrosion inevitably occurs during the use of alloys, making their corrosion resistance a special requirement for their application under specific conditions. The environmental corrosion behavior of alloys, seawater corrosion behavior, corrosion resistance, and microstructure of high‐entropy alloys (HEAs) have been prominent research topics over the past decade, all of which warrant further investigation. The corrosion resistance and passivation film strength of HEAs could be enhanced by improving their microstructure with appropriate adjustments of their elemental composition and content. In this review, the research status and corrosion mechanism of HEAs in seawater solutions with NaCl as the main component were examined. Moreover, the correlation between the microstructure, elemental composition, and corrosion resistance of HEAs was revealed.

Study on microstructure and corrosion resistance of CoCrFeNiTi0.2Mox high entropy alloy

Vacuum arc melting was employed by produting the high entropy alloys CoCrFeNiTi0.2Mox (x=0, 0.1, 0.3). We investigated the influence of Mo on the phase, microstructure, and corrosion resistance of CoCrFeNiTi0.2Mox (x=0, 0.1, 0.3). The introduction of Mo led the high entropy alloy to shift to a double-phase structure, with a rise in the volume percentage of σ phase. The corrosion resistance of high-entropy alloys decreases first and subsequently increases with increasing Mo content in 3.5 weight percent NaCl solution.

Corrosion behavior of AlCrVTi light-weight high-entropy alloy coating in different corrosion environments

The excellent corrosion resistance of high-entropy alloys (HEAs) has attracted widespread attention in recent years. The focus of research is gradually shifting from the performance characterization to the composition design and application that balance multiple performance. In this study, the AlCrVTi light-weight HEA has been chosen to investigate the corrosion behavior in the electrochemical and salt spray environment. The results show that HEA coating prepared by plasma spray followed laser re-melting present a homogeneous single-phase microstructure. The active Ti and V elements promote the formation of passive film during corrosion, which improves the corrosion resistance of HEA coating. Therefore, the HEA presents a higher corrosion resistance compared with 304 stainless steel (SS304), which is reflected in the lower corrosion current density. In the salt spray environment, the coating still presents the pitting corrosion, which is same as in the electrochemical environments. It is demonstrated that the AlCrVTi HEA has the potential that balancing the corrosion resistance and mechanical properties.

Mechanical properties and corrosion resistance of AlxCoCuFeMn high-entropy alloys

In the engineering application of alloys as structural materials, the mechanical properties and corrosion resistance are the key factors that need to be considered, and which are closely related to the microstructure. The effects of Al on the microstructure, mechanical properties and corrosion resistance of AlxCoCuFeMn (x = 0, 0.25, 0.5, 0.75, 1) high-entropy alloys (HEAs) have been investigated in the present work. The results indicate AlxCoCuFeMn HEAs have a typical dendritic structure, the Al free CoCuFeMn HEA has a Cu-rich FCC1 phase in interdendrites region and a Fe–Co rich FCC2 phase in dendrite region. When the content of Al increases, the fraction of FCC1 phase precipitated in the dendrite region, the FCC2 phase gradually developed into BCC&B2 phases, and finally only FCC1 and BCC&B2 phases were left in AlCoCuFeMn. With increasing of Al contents, the hardness and compressive yield strength of HEAs increased monotonically from 175 HV, 434 MPa to 463 HV, 1342 MPa, respectively. Meanwhile, the mass density decreased from 7.94 g/cm3 to 6.99 g/cm3 with increasing Al contents. The corrosion resistance of HEAs are ameliorated as the Al content increased. Among the five HEAs, AlCoCuFeMn shows remarkable comprehensive corrosion resistance, for which, the Ecorr and Icorr values are found to be −0.342 V and 5.53 × 10−6 A cm−2. The results of present study are useful to design low-cost corrosion-resistant HEAs with high strength.

Microstructural evolution, mechanical properties and corrosion resistance of CoCrFeNiW0.5 high entropy alloys with various annealing heat treatment

High entropy alloys (HEAs) with excellent mechanical properties and corrosion resistance show promising potential for use in many fields including marine environment. In order to make a good tradeoff between the mechanical properties and corrosion resistance, the microstructure of HEA is adjusted by proper heat treatment. Herein, the non-equiatomic CoCrFeNiW 0.5 HEA with dual FCC and μ phase was prepared by using an electromagnetic levitation melting method, and the microstructure, mechanical properties and corrosion resistance of these alloys with annealing temperature range from 600 to 1200 °C for 3 h have been investigated. After annealing at 1000 °C, a large number of needle-like μ phase precipitates was firstly observed in the matrix, the volume fraction of the μ phase is 26.64 %, which is about twice as higher as under the as-cast conditions (13.35 %). This alloy exhibited the highest compression yield strength of 1253.9 MPa with a considerable fracture strain of 40.8 % and the highest Vickers hardness value of 369.6 HV. The decomposition of μ phase precipitates was observed when annealing temperature up to 1200 °C, which lead to the mechanical properties of the alloy decreased slightly. All the alloys were found to show excellent corrosion resistance in 3.5 wt% NaCl solution, and corrosion occurs preferentially on the FCC matrix and phase boundaries, the increase of μ phase volume fraction result in more severe galvanic corrosion of alloys. Our results offer insights into analyzing the evolution of both mechanical properties and corrosion resistance of HEAs caused by heat treatment. • Heat treatment between 600 and 1200 °C lead to the change of μ phase precipitates. • CoCrFeNiW 0.5 HEA exhibited the highest compression yield strength of 1253.9 MPa with a fracture strain of 40.8 %. • The potential difference between FCC and μ phase intensifies the corrosion. • Phase volume ratio can influence the mechanical properties and corrosion resistance.

Influence of the Dispersion Hardening with Nanooxides on the Corrosion Resistance of High-Entropy Alloys of the Cr–Fe–Mn–Ni System in Lead Melts

Influence of the Dispersion Hardening with Nanooxides on the Corrosion Resistance of High-Entropy Alloys of the Cr–Fe–Mn–Ni System in Lead Melts

High entropy alloys and Corrosion resistance –A Bird’s eye view

Abstract The introduction of high entropy alloys (HEA) concept broke up the traditional rule that the main elements take up more than 50% atomic content. HEA means that alloys are composed of multi elements and each takes up a relatively high but less than 35% of atomic content. The properties of this innovative alloy are decided by the combined action of multi elements. HEA tends to form simple crystallization phase. By controlling the composition , it is possible to achieve high-hardness and high-abrasion performance at high temperature, Microstructure and properties of several HEAs prepared by various methods such as powder metallurgy laser cladding etc, are discussed. The corrosion resistance of HEAs are also discussed . KEYWORDS: High entropy alloys, corrosion resistance, micro structure, properties, applications