Lightweight High Entropy Alloy Research Articles

Machine Learning Phase Prediction of Light-Weight High-Entropy Alloys Containing Aluminum, Magnesium, and Lithium

With the development of society, there is an increasingly urgent demand for light-weight, high-strength, and high-temperature-resistant structural materials. High-entropy alloys (HEAs) owe much of their unusual properties to the selection among three phases: solid solution (SS), intermetallic compound (IM), and mixed SS and IM (SS and IM). Therefore, accurate phase prediction is crucial for guiding the selection of element combinations to form HEAs with desired properties. Light high-entropy alloys (LHEAs), as a significant branch of HEAs, exhibit excellent performance in terms of specific strength. In this study, we employ a machine learning (ML) method to realize the design of light-weight high-entropy alloys based on solid solutions. We determined the Gradient Boosting Classifier model as the best machine learning model through a two-step feature and model selection, in which its accuracy and F1_Score achieve 0.9166 and 0.8923. According to the predicted results, we obtained Al28Li35Mg15Zn10Cu12 LHEAs, which are mainly composed of 90% solid solution. This alloy accords with the prediction results of machine learning. But it is made up of a two-phase solid solution. In order to obtain a light-weight high-entropy alloy dominated by a single solid solution, we designed Al24Li15Mg26Zn9Cu26 LHEAs on the basis of machine learning prediction results accompanied by expert experience. Its main structure includes a single-phase solid solution. Our work provides an alternative approach to the computational design of HEAs and provides a direction for future exploration of light-weight high-entropy alloys.

Phase Formation of Novel Al-Mg-Zn-Cu-Si Lightweight High Entropy Alloy

In this paper, a novel lightweight and low-cost Al35Mg20Zn15Cu10Si20 at. % (Al26.17Mg13.47Zn27.18Cu17.61Si15.57 wt.%) has been successfully designed, produced, and characterized. The thermophysical parameters were used to understand the phases associated with this alloy that show a low density of 3.42 g/cm3. The designed alloy was manufactured using both the arc and the muffle furnace. The alloy was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS). The alloy is characterized by a multiphase microstructure with three major phases including Mg2Si intermetallic phase and eutectic. The volume fraction of the eutectic and the intermetallic phases are 37.83 and 34.99 respectively. The heat capacities of the alloy were also determined by means of differential scanning calorimetry (DSC). The alloy provides a high latent heat of up to 124 J/g, which is one of the highest among the high-temperature metallic materials. The present work provides valuable information for researchers wishing to design and manufacture industrial-grade high-entropy alloys (HEAs).

Constitutive behavior of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high entropy alloy

The constitutive behavior of engineering materials can predict the change of flow stress with processing parameters, which is of great significance for the selection of processing parameters. In the present work, the constitutive behavior of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high entropy alloy was investigated by using thixotropic compression tests performed at semi-solid temperatures ranging from 500 °C–530 °C with strain rates ranging from 0.01 s−1–1 s−1, and the microstructure evolution was observed. The results indicate that the thixotropic compression deformation process of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high entropy alloy can be divided into three stages: the flow stress increasing stage, the flow stress decreasing stage and the steady-state flowing stage. The peak stress of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high entropy alloy increases with the increase of strain rate. With the increase of deformation temperature, the peak stress decreases obviously. A reasonable constitutive model of the peak stress of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high entropy alloy as a function of strain rate, deformation and liquid fraction was obtained. The average relative error between the calculated and experimental values is 6.35%.

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.

Hydrogen storage properties of Mg0.10Ti0.30V0.25Zr0.10Nb0.25 lightweight high entropy alloy: A theoretical study

In the past several years, Mg-based high entropy alloys (HEAs) have attracted great attention in high gravimetric hydrogen storage capacity. In this work, the hydrogen storage properties of Mg0.10Ti0.30V0.25Zr0.10Nb0.25 HEA are investigated by first-principles calculations. With increasing hydrogen concentration, the structural stability of BCC and FCC hydrides decreases and increases, respectively. By comparing the lattice constants, number of hydrogenation-induced abnormal short hydrogen-hydrogen bonds and radial distribution functions of BCC and FCC hydrides, it is found that the hydrogen accommodation ability of BCC phase is weaker than that of FCC phase, and a BCC to FCC phase transformation occurs during hydrogenation process. Further total energy calculations suggest that the threshold hydrogen content of phase transformation for Mg0.10Ti0.30V0.25Zr0.10Nb0.25 is around H/M = 1.16. By phonon spectra calculation, the maximum gravimetric hydrogen storage capacity of Mg0.10Ti0.30V0.25Zr0.10Nb0.25 is predicated to be as high as 3.16 wt%, demonstrating that Mg0.10Ti0.30V0.25Zr0.10Nb0.25 HEA is a potential hydrogen storage material.

A novel laser-cladded AlCuTiVCr/Cu-Al functionally graded coating with excellent corrosion resistance on Mg-Li alloy

AlCuTiVCr/Cu-Al lightweight high-entropy alloy gradient coating was successfully prepared by laser cladding to improve the corrosion resistance of Mg-Li alloy. The boundaries between AlCuTiVCr protective layer, Cu-Al transition layer and Mg-Li alloy substrate are distinct, forming an excellent metallurgical bonding. The gradient coating design has effectively balanced the thermal matching difference between HEA coating. The prepared AlCuTiVCr protective layer comprises (V, Cr)-rich BCC1, Mg-rich BCC2, AlCu2Ti and β-Ti phases. The Cu-Al transition layer is composed of β-Li, Cu2Mg and Al2Cu3 phases. The corrosion potential of AlCuTiVCr protective layer (−0.46 VSEC) is 1.09 VSEC higher than that of Mg-Li alloy (−1.55 VSEC), while the corrosion current density of the protective layer (9.41 × 10−7 A cm−2) is about three orders of magnitude lower than that of the substrate (5.97 × 10−4 A cm−2).

Tribological performance of a novel 7068-aluminium/lightweight-high-entropy-alloy fabricated via powder metallurgy

This investigation was designed to determine the effect of Al30(Li2MgBe2TiCu)10 lightweight high-entropy alloy (LHEA) of density 2.43 g/cm3 at proportions of 4, 10, and 16 wt% on the tribological performance of aluminum 7068 alloy when exposed to applied loads of 10, 20, 30, and 40 N. During the wear process, the microstructure of the composite exhibited surface fractures, delamination, material loss, oxide film formations, and fragmented debris, from which abrasive, adhesive, and oxidative wear mechanisms were deduced, as well as delamination by plastic deformation. Examination of wear debris revealed that the LHEA particles had a major effect in reducing the average coefficient of friction and enhancing wear resistance. It was revealed that the 10 wt% LHEA infusion in the composite reflected the desired tribological performance.

Applicability of Extreme Vertices Design in the Compositional Optimization of 3D-Printed Lightweight High-Entropy-Alloy/B4C/ZrO2/Titanium Trihybrid Aero-Composite

Recent studies have shown the benefits of utilizing ceramic particles as reinforcement in metal alloys; nevertheless, certain drawbacks, including loss of ductility, embrittlement, and decreases in toughness, have been noted. For the objective of obtaining balanced performance, experts have suggested the addition of metal particles as supplement to the ceramic reinforcement. Consequently, high-performance metal hybrid composites have been developed. However, achieving the optimal mix for the reinforcement combination with regards to the optimal performance of developed composite remains a challenge. This research aimed to determine the optimal mixture of Al50Cu10Sn5Mg20Zn10Ti5 lightweight high-entropy alloy (LHEA), B4C, and ZrO2 for the fabrication of trihybrid titanium composites via direct laser deposition. A mixture design was involved in the experimental design, and experimental data were modeled and optimized to achieve the optimal performance of the trihybrid composite. The ANOVA, response surface plots, and ternary maps analyses of the experimental results revealed that various combinations of reinforcement particles displayed a variety of response trends. Moreover, the analysis showed that these reinforcements significantly contributed to the magnitudes and trends of the responses. The generated models were competent for predicting response, and the best formulation consisted of 8.4% LHEA, 1.2% B4C, and 2.4% ZrO2.

Light Weight MnTiAlNiFe High-Entropy Alloy (LWHEA) Fabricated by Powder Metallurgy Process: Mechanical, Microstructure, and Tribological Properties

The present work is focused on the development of lightweight high entropy alloy (LWHEA) using a powder metallurgy process. The primitive powders of manganese (Mn), titanium (Ti), aluminum (Al), nickel (Ni), and iron (Fe) with a purity of ∼ 99.5 % and particle size in the range of 40 to 70 µm were considered as a raw material for the synthesis of present LWHEA. The elemental powders at an equal molar ratio were mechanically alloyed (MA) in a high-energy ball milling for 28 hrs. The MA powders were then cold compacted using 500 MPa pressure, followed by sintering at 900 °C in an inert atmosphere to produce a bulk cylindrical sample of 8 mm diameter and 8 mm height. The average particle size of the milled powders was measured by FESEM image analysis, while the crystal size of the milled powders was predicted from the XRD peak broadening followed by full-width half maximum (FWHM) peak profile calculation using the Hall-Williamson method. The BCC structure, along with intermetallic phases, was identified in the sintered bulk LWHEA of MnTiAlNiFe. Some intermetallic phases act as reinforcement in the alloy. The EDX analysis of MA powder revealed that all the elemental powders were distributed homogeneously to form a solid solution of LWHEA powder. The deformation behavior of the sintered MnTiAlNiFe LWHEA was studied by analyzing the loading–unloading curve of micro indentation. A remarkable improvement in the hardness values (microhardness ∼ 7.382 GPa and Martens hardness ∼ 3.09 GPa at 3 N load) was observed compared to conventional lightweight metallic alloys. The investigation of the wear behavior of the bulk MnTiAlNiFe LWHEA samples carried out in a Universal Tribometer coupled with a 3D optical profilometer predicts the load-dependent coefficient of friction of the sample.

Experimental research on mechanical performance of the lightweight composite slabs Research Progress on the Lightweight High-Entropy Alloys

The high-entropy alloy, a new multi-principal element alloy, contains light elements to obtain the lightweight high-entropy alloy (HEA) with the outstanding property of low densities. Its high strength and hardness, corrosion resistance, and high-temperature resistance allow it to be broadly applied in aerospace, transportation, etc, which has attracted wide attention and research. Its research status is described and its component design methods are classified in this paper. Meanwhile, this paper summarizes its microscopic phase structure and properties of different kinds, including hardness, strength, corrosion resistance, and high-temperature resistance. Finally, its application prospect and the shortcomings of current research are also summed up.

A metastable lightweight high entropy alloy with the transformation induced plasticity

Body-centered cubic (BCC) high entropy alloys (HEAs) usually have poor ductility, limiting their engineering application. Here we present a TiZrNbAl non-equal atomic-ratio HEA (Z25) which shows martensitic transformation during tensile deformation. This transformation effectively improved the uniform ductility to around 17%. The gradually induced martensite lamella shows the “dynamic Hall-Petch” effect during transformation, which reduces the mean free path of dislocation slip, resulting in Z25 alloy with excellent ductility and remarkable work hardening effect.

Investigation on microstructures and properties of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy during isothermal heat treatment process

The Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy with globular microstructure was fabricated by isothermal heat treatment. The effects of isothermal temperatures and holding times on the semi-solid microstructure evolution were investigated. The results indicate that, with increase of the isothermal temperature, the average grain size increases and the spheroidization time shortens. With prolongation of holding time, the shape factor increases firstly and then decreases, and the average grain size decreases at first and then increases when the isothermal temperature is below 520 °C, however it increases gradually at 540 °C. The optimal semi-solid microstructure is obtained at 520 °C for 30 min, whose shape factor and average grain size are 0.90 and 56.4 µm, respectively. Compared with as-cast Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy, the compressive strength and plasticity of semi-solid Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy are increased by 36% and 108%, respectively. The formation of semi-solid microstructures includes three stages: melting separation, spheroidization, and coarsening growth. The sluggish diffusion effect of Al80Mg5Li5Zn5Cu5 light-weight high-entropy alloy leads to a low coarsening rate, resulting in slow grain growth.

Design and characterization of a novel MgAlZnCuMn low melting point light weight high entropy alloy (LMLW-HEA)

Development of high-entropy alloys (HEAs) is one of the remarkable advancements in the progress of new materials. In recent years, continuous efforts have been made to design light weight high-entropy alloys (LWHEAs) with suitable microstructure and superior properties. This paper reports the preliminary results of a study aimed at design and development of a new low melting point LWHEA (LMLW-HEA) based on AlMgZnCuMn alloy system without excessive intermetallic compounds formation. In this research, first, the initial chemical composition of the alloy was designed according to thermodynamic parameters, and then the alloy was melted in a resistance electric furnace. Since the thermodynamic indicators have been defined based on alloys containing 3d transition elements, formation of binary intermetallic compounds was predicted with the help of Midema model. To investigate the effects of cooling rate and heat treatment on the structure of the designed alloy, the molten alloy was poured into two different molds made of silica sand and steel, and both as cast samples were also heat treated. Microstructural features, mechanical properties and thermal stability of the samples were then examined. Density of the samples was measured to be less than 3.4 gr/cm3 which was very close to the theoretical density of the alloy. Structures of all the samples were complex and multi-phase and contained intermetallic (ordered solid solution) binary and ternary compounds including Mg7Zn3, MgZn2, Cu2Mg, Al2Cu, Mg32 (Al, Zn)49, Mg32Cu7Al47, Al25Mg37.5Zn37.5, and CuMgZn phases. The designed alloy was brittle under all the processing conditions. Compressive strength of the alloy reached to about 95 MPa, and its hardness was in the range of 110–120 HV. Oxidation resistance of the alloy was evaluated at a temperature about 30 °C below its solidus temperature and no weight change was observed in the sample after 14 h. It is suggested that the designed alloy is a suitable candidate for high temperature applications not involving impact or cyclic loading.

Preparation and microstructure and properties of AlCuFeMnTiV lightweight high entropy alloy

A new type of AlCuFeMnTiV lightweight high entropy alloy (LWHEA) was prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The effects of milling time on the phase evolution of alloy powders and sintering temperature on the microstructure and mechanical properties of alloy blocks were investigated. The results show that the powders can be alloyed after 36 h high-energy ball milling, forming a BCC solid solution, and the alloying sequence is related to the melting point of the alloy elements. After being sintered by SPS, the alloy block is mainly composed of the BCC matrix, and the B2 phase (ordered BCC phase) and the HCP phases are precipitated from the matrix during the sintering process. Besides that, the Cu-rich FCC phase is distributed at grain boundaries. Nano twins are found in some FCC phases, which have a good strengthening effect on the grain boundary so that the alloy maintains high strength and good plasticity. The block sintered at 1050 °C exhibits the best comprehensive mechanical properties, with the density of 6.28 g⋅cm−3, hardness of 618.44 HV, compressive strength and yield strength of 2630 MPa and 2060 MPa respectively, the plastic strain of 15.83% and specific strength of 418.79 MPa⋅cm3⋅g−1, which is superior to most LWHEAs and traditional lightweight alloys.

Microstructure development and mechanical performance of Al2CrFeMnTi light-weight high entropy alloy

Light-weight high entropy alloys (LWHEAs) are considered equiatomic or near-equiatomic alloys consisting of at least five elements. Low-density elements, like Al and Ti, are the key constituents in designing these alloys so that features such as reduced overall density and improved mechanical properties are achieved.A new LWHEAs (Al2CrFeMnTi) is designed, where mechanical alloying followed by subsequent casting is carried out for a successful synthesis. As a result, chemically homogenous samples are fabricated that possess a multiphase microstructure of BCC solid solution, C14 Laves phase, and L21 precipitates in the as-cast state. Although the presence of intermetallic phases results in high hardness characterized by nanoindentation tests, the produced alloy demonstrates some level of ductility before failure. This behavior could be linked to the minimal strain hardening of the BCC phase. Additionally, the formation of ultra-fine L21 precipitates within the BCC phase is contributed to the high strength and the modified strain observed in the alloy.

Lightweight AlCuFeMnMgTi High Entropy Alloy with High Strength-to-Density Ratio Processed by Powder Metallurgy

In this study, we synthesized a new Al16.6Cu16.6Fe16.6Mn16.6Mg16.6Ti16.6 lightweight high entropy alloy (LWHEA) by high energy ball milling and spark plasma sintering (SPS). The effect of milling time (15, 30, 45, and 60 h) and SPS conditions (600 and 700 °C) on microstructure, hardness, and density of LWHEAs were studied. The results showed that milled LWHEA is base centered cubic (BCC) structured, consisting of dual BCC1/BCC2 matrix with dispersed minor Cu2Mg precipitates and Ti. After SPS of milled samples, the BCC2 phase fraction was increased gradually. The distribution of Ti was uniform up to 45 h milled sample SPSed at 600 °C. However, porosity was built up beyond 45 h milling and higher SPS temperature (700 °C). The presence of finer secondary phases in the HEA matrix contributes to the dispersion hardening. The optimum microhardness and density of LWHEA AlCuFeMnMgTi were around 770 HV and 4.34 g cm− 3 which is superior to other conventional alloys such as Al or Ti-based alloys.

Microstructural evolution and mechanical properties of non-Cantor AlCuSiZnFe lightweight high entropy alloy processed by advanced powder metallurgy

In this study, multicomponent AlCuSiZnFe high entropy alloy (HEA) was fabricated through high energy ball milling (HEBM) of constituent powders, and further densification via spark plasma sintering (SPS). The results show the presence of a predominant face-centered cubic (FCC) phase with a minor body-centered cubic (BCC) phase in (45 h) HEBMed powders which further develop according to the SPS treatment. At a low SPS temperature of 600 °C, the alloying of individual elements was poor. Further, at 650 °C, alloying improves and the liquid Cu–Zn FCC phase separates from the high-temperature Fe–Si-rich BCC phase during SPS. At 700 °C, Al was noticed to stabilize the BCC phase leaving behind soft FCC (Cu–Zn). Further increase in SPS temperature to 800 °C causes a complete melting of HEA compacts and the formation of Cu–Al intermetallic compounds (IMCs). The microhardness of the HEA compacts increases with SPS temperature in the range of 690–974 HV. The compressive properties were found to be optimum at 650 °C, compressive strength ≈1987 MPa and elastic modulus ≈27,945 MPa respectively. The measured densities of HEAs varied from 4.98 to 5.24 g/cm3, comparable to the heaviest of lightweight Ti alloys reported so far.

Development of a novel light weight Al35Cr14Mg6Ti35V10 high entropy alloy using mechanical alloying and spark plasma sintering

A new light-weight high entropy alloy (LWHEA) composition Al35Cr14Mg6Ti35V10 is designed using the thermodynamic parameters of stability with a density of 4.05 g cm−3. The alloy was prepared by mechanical alloying (MA) using a high-energy planetary ball milling and compacted by using spark plasma sintering (SPS). X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and hardness testing were used for analysis of the ball-milled powders and bulk sample. After 30h of milling a single-phase BCC was obtained with some minor impurities of WC. After SPS, the final microstructure was having one HCP and two BCC phases with minor contamination of WC embedded into it. The hardness of a light-weight Al35Cr14Mg6Ti35V10 alloy was found to be 460 HV which is superior to other Al, Mg, and Ti-based conventional alloys.

Ordering induced transformation from high-entropy to Heusler CrVTiAl alloy

The equimolar quaternary CrVTiAl is not only a potential spin filter, but also a light-weight high entropy alloy. The excellent performance strongly depends on the order degree. We use the ab initio calculation to investigate the structural, magnetic, elastic properties of CrVTiAl as a function of the order degree describing phase from full disorder A2 to DO3, B2, and L21 to full order Y-type (LiMgPdSn-type) structure. The Cr-Al bonding plays a key role in the local magnetic moments, further induces the increasing lattice parameter and decreasing elastic constants. Furthermore, the effect of preferred sites on mechanical properties is discussed.

Phase stability and transformation in a light-weight high-entropy alloy

Light-weight high-entropy alloys (HEAs) with a vast alloy-design space have offered new avenues to explore novel low-cost, high strength-to-weight ratio structural materials. Studying their phase stability and possible transformations is critical for designing microstructures for optimal material properties. However, the complex local atomic environment of HEAs poses challenges to the fundamental understanding of phase stability and transformation behaviors. The present study investigates the phase stability and transformation behaviors of a newly-designed light-weight Al1.5CrFeMnTi HEA by integrated experimental and theoretical approaches. The coherent precipitation of the L21 phase within the body-centered-cubic (BCC) matrix at intermediate temperatures was observed, and the size, shape, coherency, and spatial distribution of the L21 phase were subsequently altered through selected annealing treatments. Moreover, the CALculation of PHAse Diagrams (CALPHAD) and first-principle calculations successfully optimize the compositions of light-weight HEAs with a coherent BCC/L21 two-phase structure. Shed light by the present study, novel light-weight HEAs, featuring the lower density (below 6 g/cm3) and cost, can be designed for high-temperature applications.