High-entropy Alloy Composites Research Articles

Fabrication, microstructure, and mechanical properties of Al-based metal matrix-TiB2 -HEA hybrid composite

In this work, a metal matrix composite is made up of a cast Al-Si-Mg alloy (LM25) matrix with two variants of particle reinforcements, first one with 3 wt% TiB2 and 2 wt% CoCrFeMnNi high entropy alloy (HEA) and the other as 2 wt% TiB2 and 3 wt% CoCrFeMnNi (HEA) were used. These two composites were successfully fabricated through the stir-casting process. The microstructures and morphology of the developed composites are studied using TEM and SEM. In the fabricated composites, TiB2 and HEA particles were discovered to be evenly dispersed in the matrix phase. The XRD analysis showed the existence of both the reinforcement phases TiB2 and HEA particles along with the matrix phase. The mechanical properties were enhanced with the addition of the reinforcement phase when compared with the base metal. It is also observed that the tensile strength is enhanced with increased HEA content demonstrating almost same ductility. The LM25–2 wt% TiB2 − 3 wt% HEA composite demonstrated higher tensile strength (∼255 MPa) than the LM25–3 wt% TiB2-2 wt% HEA composite (∼230 MPa) and LM25 base alloy (∼160 MPa) due to the presence of TiB2 and HEA particles and the high dislocation density and contrasted very well in terms of strength and ductility with conventional LM25 matrix composites supplemented with ceramic particles. The mode of fracture was observed that the cleavage planes on the fracture surface with increasing with HEA content changes from dimple morphology of base metal.

A simple phenomenological model to describe stability of homogeneous solid solutions in high entropy alloys from metallic bonding potential

A simple model based on the potential parameters used to describe metallic bonding is extended to solid solutions. A figure of merit (an effective temperature, Teff) is proposed using a simple average over the potential coefficients to discern whether a homogeneous solid solution is expected to be stable or not in high entropy alloy compositions. Teff is calculated as the ratio between the solid solution excess in bonding energy over the average mixture divided by the configurational entropy. Application to the sexinary AlCrCuFeNiCo system stablishes a stability threshold for Teff<500 K. The model can successfully describe both the deviations from Vegard's law observed in binary alloys and the differences in this parameter between B2 ordered and bcc disordered phases considering average potential coefficients over the different possible atomic couples.

Development and characterization of boride-reinforced CoCrFeNi composites

CoCrFeNi is a face-centered cubic (FCC) high entropy alloy (HEA) that exhibits high ductility both at room temperature and at cryogenic temperatures but has limited strength. The present study is focused on addition of TiB2 to the CoCrFeNi HEA with the goal of developing materials with better combinations of strength and ductility. HEA composites with varying amounts of TiB2 were prepared by arc melting under an argon atmosphere. The resulting alloys were subjected to chemical, microstructural, and mechanical characterization. Interaction of TiB2 with chromium in the HEA matrix during melting resulted in its decomposition, leading to in-situ formation of chromium borides with plate morphology. A eutectic mixture, consisting of a hard phase (chromium boride) and a tough phase (the FCC matrix) was also developed with the amount of the eutectic mixture increasing with increasing amount of TiB2 added to the HEA. Mechanical characterization of the developed composites revealed a very wide range of mechanical properties, including yield strengths ranging from 180 MPa to 1282 MPa, hardness values ranging from 200 to 750 HV, and elongation ranging from 3.4% to more than 60%. Outstanding combinations of mechanical properties could also be obtained, for example the HEA composite developed by addition of 6 wt% TiB2, exhibited very high hardness (400 ± 10 HV) and very high yield strength (918 MPa), along with very good values of elongation before fracture (30%). The results in this study demonstrate that development of ceramic-reinforced HEA composites can help in obtaining alloys with excellent combinations of strength and ductility.

Design Tool Predicts Mechanical Properties and High-Temperature Performance of High-Entropy Alloys

Abstract This article describes new software that helps predict properties of high-entropy alloy compositions under high-temperature conditions. The tool was developed by extensive testing on the quinary Al-Co-Cr-Fe-Ni alloy system with both first-principles density functional theory calculations and machine learning to establish a substantial database for modeling.

Phase engineering in nanocrystalline high-entropy alloy composites to achieve strength-plasticity synergy

In this work, the strength-plasticity synergy of Al/CoCrFeNi nanocrystalline high-entropy alloy composite (nc-HEAC) prepared by laser-inert gas condensation is achieved via nanoscale diffusion induced phase transition (DIPT) process. The yield strength and elongation of the 16%-Al/CoCrFeNi nc-HEAC annealed at 900 °C were 1338 MPa and 12.1%, showing the combination of outstanding strength and considerable ductility. The synergy of multiple strengthening mechanisms were revealed. Driving the phase transition of nanocrystalline dual-phase composites by thermal diffusion establishes a novel phase engineering design strategy for high-performance alloys.

Effect of NiCoFeAlTi high entropy intermetallic reinforcement particle size on the microstructure and mechanical properties of CoCrFeMnNi high-entropy alloy composites fabricated by selective laser melting

The particle size of the reinforcement affects the microstructure and mechanical properties of the composites fabricated by selective laser melting. The powder bed characteristics were greatly influenced by the size of the powder particles. In this research, CoCrFeMnNi high entropy alloys (HEAs) were reinforced with NiCoFeAlTi high entropy intermetallics (HEI) where two different reinforcement sizes were utilized. The microstructure and mechanical properties of CoCrFeMnNi HEA matrix with NiCoFeAlTi HEI reinforcement with varying particle sizes were investigated systematically. The composites reinforced with fine particle size exhibit stress-induced intergranular cracking, element segregation, and poor mechanical properties. On the other hand, composites reinforced with coarser particle size display crack and pore-free microstructure with uniform compositional distribution and relatively outstanding mechanical properties. This work contributes to a further understanding of the influence of reinforcement particle size on the crack-sensitive composites fabricated by selective laser melting.

Hierarchical microstructures and strengthening mechanisms of nano-TiC reinforced CoCrFeMnNi high-entropy alloy composites prepared by laser powder bed fusion

High entropy alloys (HEAs) have recently received extensive attention due to their appealing mechanical performance given their simple phase formation. This study utilized laser powder bed fusion (LPBF) to fabricate high-performance HEA components. By processing respective powder blends, LPBF enabled the fabrication of stronger composites with a uniformly distributed reinforcing phase. Here, the impact of varying content of nano-scale TiC (1 wt.%-3 wt.%) particles for strengthening the CoCrFeMnNi HEA was explored. The microstructural features and mechanical properties of the HEA composites were investigated in detail. The introduction of nano-scale TiC into the HEA matrix encouraged the development of cross-scale hierarchical microstructure and eliminated the formation of oxide inclusions. Incorporating more nano-TiC led to a higher dislocation density and more refined microstructure in the HEA composites, whereas posed little influence on the anisotropy of the HEA matrix which typically featuring a <001> texture along the building direction. With an optimized content of nano-TiC (1 wt.%-2 wt.%) used, the strength-ductility trade-off can be overcome by exploiting multiple strengthening mechanisms encompassing grain boundary strengthening, solid solution strengthening, Orowan strengthening, and dislocation strengthening. The HEA composites showed a favored strength-ductility combination with a yield strength of 748-882 MPa, ultimate tensile strength of 931-1081 MPa, and fracture elongation of 23%-29%. This study demonstrates that introduction of nano-scale TiC is an effective way to simultaneously improve the strength and ductility of additively manufactured HEA materials.

The Effect of Copper on the Microstructure, Wear and Corrosion Resistance of CoCrCuFeNi High-Entropy Alloys Manufactured by Powder Metallurgy.

This paper focuses on the microstructure, phase composition, mechanical, tribological and corrosion properties of high-entropy alloys (HEAs) in the CoCrCuFeNi system depending on copper content, which was varied from 0 to 20 at. % with an increment of 5%. CoCrCuFeNi alloys were manufactured by powder metallurgy methods: mechanical alloying and hot pressing of element mixtures. The solubility limit of copper in CoCrFeNi solid solution was found to be 9 at. %. Segregation of irregularly shaped copper grains sized 1-30 μm is observed at concentrations above this solubility limit. As copper concentration increases, the phase composition of CoCrCuFeNi alloys changes from the single phase based on FCC1 solid solution (Cu = 0-5 at. %) to the dual-phase FCC1 + FCC2 alloy (Cu = 10-20 at. %), where FCC1 is the main phase and FCC2 is the secondary copper-rich phase. Tribological tests have shown that doping the CoCrFeNi alloy with copper increased wear resistance by 23% due to solid solution hardening. As copper content rises above 20%, the content of the secondary FCC2 phase increases, while wear resistance and alloy hardness decline. An analysis of wear tracks and wear products has shown that abrasion of CoCrCuFeNi alloys occurs via the abrasive-oxidative wear mechanism. The corrosion tests of CoCrCuFeNi HEAs in 3.5% NaCl solution had demonstrated that doping the alloy with copper at low concentrations (5-10%) leads to decreasing of corrosion resistance, possibly due to the formation of undesirable oxide Cu2O along with protective Cr2O3. At high copper concentrations (15-20%) galvanic corrosion is suppressed due to coarsening of FCC2 grains and thus decreasing the specific contact surface area between the cathode (FCC2) and the anode (FCC1).

Enhancing hydrogen storage properties of MgH2 using FeCoNiCrMn high entropy alloy catalysts

Herein, we report the successful preparation of the FeCoNiCrMn high entropy alloy (HEA) loaded MgH2 and HEA's effect on the hydrogen storage properties of Mg/MgH2. The HEA shows high catalytic activity toward hydrogen dissociation and recombination reaction, and successfully suppressed activation energy of dehydrogenation reaction from 151.9 to 90.2 kJ mol–1. Moreover, part of Co and Ni can react with Mg, and produce Mg2Co/Mg2CoH5 and Mg2Ni/Mg2NiH4 during the hydrogen storage processes, further enhancing dehydrogenation reaction through the “hydrogen pumping” mechanism. As a result, the MgH2–5 wt% HEA composite can release 5.6 wt% of H2 at 280 °C within 10 min, and absorb 5.5 wt% H2 within 0.5 min at 150 °C. The loaded HEA shows robustness against particle aggregation, leading to stable reversible hydrogen storage processes at least 50 times. These findings show the synergistic effects of HEA on Mg-based hydrogen storage materials, providing an additional degree of freedom for catalyst design.

Microstructure and tribological properties of in-situ carbide/CoCrFeNiMn high entropy alloy composites synthesized by flake powder metallurgy

CoCrFeNiMn high entropy alloy (HEA) owns prominent strain hardening capacity and high tensile elongation but poor wear resistance. In present work, in-situ carbide/CoCrFeNiMn composites with excellent anti-wear properties were fabricated by a flake powder metallurgy route using graphene oxide (GO) and CoCrFeNiMn as original powders. As a result, the hard carbide phase, Cr7C3, is formed in the soft matrix via in-situ reaction at the GO/HEA interface, which leads to a dense distribution of small-sized Cr7C3 and strong interfacial bonding of the composites. With the addition of 5 wt% GO, the microhardness is improved by 66.7% and the macroscopic wear rate is decreased by 78.3% as compared with CoCrFeNiMn HEA. Increased nano-scratch resistance indicates that the dense distribution of hard Cr7C3 carbide and the strong Cr7C3-CoCrFeNiMn interfacial bonding play key roles to resist the plastic flow of the HEA matrix during friction and wear. This study may provide a pathway to improve the wear resistance of HEA for engineering applications.

Additive manufacturing of high-entropy alloy composites: A review

High entropy alloy composites (HEACs) are a new class of metal matrix composites involving a second phase, such as carbides, borides, and nitrides in high entropy alloy matrices. In recent years, HEACs have attracted wide attention due to their outstanding properties. However, the preparation of HEACs encounters great challenges when using conventional casting approaches due to serious composition segregation. 3D printing techniques solved this problem and produced components with complex geometry. Therefore, 3D printing techniques have been applied to fabricating HEAC components, and a few works on this topic have been published. To accommodate the rapid development of 3D printing of HEACs, we present a state-of-the-art overview of the recent progress of HEAC 3D printing. The article begins with an introduction of HEAs and 3D-printed HEACs. The processes of HEAC powders development, including gas atomization and mechanical alloying, are presented. The 3D printing processes of HEAC powders, such as powder bed fusion and directed metal deposition, and their microstructures are discussed. The mechanical properties of 3D-printed HEACs are discussed and compared with 3D-printed HEAs and their casting counterparts, and their hardness, resistance to wear, corrosion, and oxidation are discussed. Finally, new perspectives are outlined for future research.

A review on high-throughput development of high-entropy alloys by combinatorial methods

High-entropy alloys (HEAs) are an emerging class of alloys with multi-principal elements that greatly expands the compositional space for advanced alloy design. Besides chemistry, processing history can also affect the phase and microstructure formation in HEAs. The number of possible alloy compositions and processing paths gives rise to enormous material design space, which makes it challenging to explore by traditional trial-and-error approaches. This review highlights the progress in combinatorial high-throughput studies towards rapid prediction, manufacturing, and characterization of promising HEA compositions. This review begins with an introduction to HEAs and their unique properties. Then, this review describes high-throughput computational methods such as machine learning that can predict desired alloy compositions from hundreds or even thousands of candidates. The next section of this review presents advances in combinatorial synthesis of material libraries by additive manufacturing for efficient development of high-performance HEAs at bulk scale. The final section of this review discusses the high-throughput characterization techniques that are used to accelerate the material property measurements for systematic understanding of the composition-processing-structure-property relationships in combinatorial HEA libraries.

Evaluation of the corrosion resistance of AlCoCrFeMnNi high entropy alloy hard coating applied by electro spark deposition

Although hard coatings have good resistance to wear and scratching, their corrosion resistance has decreased, failing. Improving the corrosion resistance of the hard coating has lately become a difficult subject. This work produced a newly created AlCoCrFeNiMn alloy with a high entropy using mechanical alloying and spark plasma sintering. Aluminum was added as the sixth elemental component to the chemical composition of the CoCrFrNiMn high entropy alloy to achieve this objective. Subsequently, the AlCoCrFeNiMn layer was deposited via electro-spark deposition on a substrate (ESD). To achieve a uniform layer, parameter optimization was performed, and the effects of frequency (5, 8, and 11 kHz), duty cycle (50, 60, and 70 %), and applied current (15, 25, and 35 A) were studied. Using the Vickers technique, the acquired surface microhardness of coatings was measured. The most significant measurement of hardness was around 1426 HV0.05. Using potentiostat-polarization testing and electrochemical impedance spectroscopy at room temperature, the corrosion of the coatings was evaluated. The AlCoCrFeNiMn HEA coating considerably increased the corrosion resistance of the substrate, according to the results. Corrosion rates for uncoated and coated samples were 1.44 and 0.13, respectively. At the optimal frequency of 11 kHz, the duty cycle of 60 %, and the current of 35 A, the coating exhibited the highest corrosion resistance, which was 10 times greater than the corrosion rate of the substrate. All of the coated samples displayed a passivation behavior, ascribed to the production of chromium oxide and aluminum oxide on the surface of the HEA layers due to their lower free Gibbs energy formation values. In addition, the coating's roughness was assessed, and the correlation between surface roughness and corrosion resistance was determined.

Microstructure, mechanical and tribological properties of oxide dispersion strengthened CoCrFeMnNi high-entropy alloys fabricated by powder metallurgy

Developing materials with superior strength and wear resistance has always drawn challenging research for advanced engineering applications. Herein, considerable efforts have been devoted to enhancing the strength and wear resistance of face-centered cubic (FCC)-structured CoCrFeMnNi high entropy alloy (HEA) by incorporating HfO2 nanoparticles (NPs) through a powder metallurgy approach. The phase composition, microstructure, mechanical, and tribological properties of HEA composites were investigated. The XRD results reveal that the composite powders consisted of the FCC solid solution along with minor HfO2 phases. In addition, sintered HEAs showed the major FCC phase along with minor Cr-rich and HfO2 phases. Microscopic results confirmed the uniform distribution of HfO2 NPs throughout the matrix during the milling process. With increasing HfO2 contents, the hardness of the HEAs increased from 270 ± 10 to 520 ± 10 HV, while the compressive yield strength increased from 370 to 1500 MPa, due to dispersion and grain boundary strengthening effects. Furthermore, composite HEAs showed a decrease in coefficient of friction and wear rates with increasing HfO2 content due to increased surface hardness and transition in wear mechanism from severe wear to mild abrasive wear. The present study demonstrates the feasibility of producing high-performance oxide dispersion-strengthened HEAs for advanced structural applications.

Ceramic-reinforced HEA matrix composites exhibiting an excellent combination of mechanical properties

CoCrFeNi is a well-studied face centered cubic (fcc) high entropy alloy (HEA) that exhibits excellent ductility but only limited strength. The present study focusses on improving the strength-ductility balance of this HEA by addition of varying amounts of SiC using an arc melting route. Chromium present in the base HEA is found to result in decomposition of SiC during melting. Consequently, interaction of free carbon with chromium results in the in-situ formation of chromium carbide, while free silicon remains in solution in the base HEA and/or interacts with the constituent elements of the base HEA to form silicides. The changes in microstructural phases with increasing amount of SiC are found to follow the sequence: fcc → fcc + eutectic → fcc + chromium carbide platelets → fcc + chromium carbide platelets + silicides → fcc + chromium carbide platelets + silicides + graphite globules/flakes. In comparison to both conventional and high entropy alloys, the resulting composites were found to exhibit a very wide range of mechanical properties (yield strength from 277 MPa with more than 60% elongation to 2522 MPa with 6% elongation). Some of the developed high entropy composites showed an outstanding combination of mechanical properties (yield strength 1200 MPa with 37% elongation) and occupied previously unattainable regions in a yield strength versus elongation map. In addition to their significant elongation, the hardness and yield strength of the HEA composites are found to lie in the same range as those of bulk metallic glasses. It is therefore believed that development of high entropy composites can help in obtaining outstanding combinations of mechanical properties for advanced structural applications.

Microstructure and corrosion investigation of FeCoCrNiMo0,5(MnAl)0,3 high entropy alloy produced by 316 L stainless steel scrap

FeCrCoNiMo 0,5 (MnAl) 0.3 high-entropy alloy (HEA) was manufactured via arc melting process by adding the related metal powders into scrap of 316L stainless steel for corrosion resistance tests under salt and acid conditions. Cyclic potentiodynamic polarization experiments performed under acidic conditions revealed pre-passivation due to abundance of network modifying metals in HEA composition which was further analyzed by electrochemical impedance spectroscopy. Elemental resolved analysis of leftover solutions was used to compare metal ions released during corrosion. X-ray diffraction analysis indicated the phase change in heat treated HEA samples. Non-heat treated HEA samples can be compared with stainless steel under moderate corrosion conditions and had better hardness results.

Short-range ordering heredity in eutectic high entropy alloys: A new model based on pseudo-ternary eutectics

Eutectic high entropy alloys (EHEAs) have garnered wide attention in the metal community due to their excellent castability and unique microstructures. However, the formation mechanisms of these eutectic microstructures and their compositional design remain puzzling. In this paper, we have developed a simple yet unified pseudo-ternary model to unravel the puzzle of multiple eutectics in Ni-Al-containing high entropy alloys (HEAs) deploying a combination of the chemical similarity/dissimilarity coefficient concept, CALPHAD technique and first principle molecular dynamics simulation. Using the chemical similarity/dissimilarity parameters derived from CALPHAD model parameters and the eutectic valleys of Ni-Al-Cr, we reproduce the multiple eutectic patterns in the Ni-Al-containing HEAs and present a general approach for pinpointing the composition of eutectic HEA (EHEA) in the vast temperature-composition space. Aided by the first principle molecular dynamics calculation, we have shown that although the eutectic structures of Ni-Al containing EHEAs are different, the formation mechanism of the eutectic structure is similar, which stems from the short-range-ordering (SRO) heredity of EHEA liquid from the eutectic valleys of the pseudo Ni-Al-Cr ternary. Two EHEAs, EHEA 1 (Al16.95Cr16.95Fe19.1Ni47) with L12+B2 eutectic structures and EHEA 2 (Al33.5Cr33Co4Ni29.5) with BCC+B2 eutectic structures were designed using the model and experimentally verified. This unified Ni-Al-Cr ternary model, validated by experimental data in both literature and our fabricated EHEAs, presents a compelling solution to the long-debated grouping strategy in EHEA design and offers a new paradigm to map the complicated but intriguing eutectic microstructures in EHEAs and conventional alloys.

Wear characteristics of laser-deposited AlCoCrCuFeNi high entropy alloy with finite element analysis

BackgroundWear is a destructive phenomenon and one of the principal causes of material failure in moving components during surface interaction while in service. AlCoCrCuFeNi high-entropy alloy with its many properties is a potential material for aero-engine applications attributed to its outstanding relatively lightweight, high strength, good thermal, oxidation, and corrosion resistance properties. Hence, the investigation into the tribological behaviour of AlCoCrCuFeNi high-entropy alloys is essential to reduce maintenance costs and prolong the service life of this advanced material for aerospace applications. Most AlCoCrCuFeNi high-entropy alloy compositions were fabricated via arc melting, which has been reported to have defects attributed to slow solidification, consequently reducing the mechanical properties of the alloy with limited reports on other fabrication methods. Therefore, there is a need for the use of advanced manufacturing techniques for fabricating these alloys to improve the tribological properties. In this study, AlCoCrCuFeNi high-entropy alloy was fabricated via laser metal deposition. The influence of the laser processing parameters, rapid solidification, and the applied load on the tribological properties of the as-built alloys under dry conditions has been studied for aerospace applications. The counter ball rolling friction analysis was also investigated using COMSOL Multiphysics.ResultsThe results showed that at a high laser power of 1600 W and a scan speed of 12 mm/s, the lowest wear rates and highest hardness values were observed. The average coefficient of friction at room temperature was 0.1 and 0.3 at a speed of 21 m/s. The dominant wear mechanism at room temperature was abrasive wear as the wear rate increased linearly with an increase in load from 10 to 20 N. The scan speed had the most significant influence on the wear behaviour of the as-built high-entropy alloy attributed to the rapid rate of solidification which occurs at higher scan speeds.ConclusionsThe study examines the wear characteristics of high-entropy alloys fabricated via laser deposition technique in comparison with those fabricated via conventional routes. Although there were similarities in the phase structures of both techniques, the results showed that the wear resistance of the laser-deposited high-entropy alloy was comparatively higher than the same alloy prepared via conventional methods. Laser additive manufacturing was concluded to be a more successful method in fabricating high-entropy alloys.

Effect of the amount of SiC particles on the microstructure, mechanical and wear properties of FeMnCoCr high entropy alloy composites

Ceramic particle reinforced high entropy (HEA) alloy composites have attracted considerable attention due to their excellent combination of strength, ductility, and wear resistance. In this work, the high entropy alloy composites (Fe 50 Mn 30 Co 10 Cr 10 matrix) with the different SiC contents (0.1, 0.5, 1, and 3 vol%) were fabricated by arc melting. The effect of SiC content on microstructure characteristics, mechanical and wear properties of Fe 50 Mn 30 Co 10 Cr 10 composites were studied. The results showed that SiC stabilized the γ phase and refined the grain sizes. In addition, the number of ε variants were decreased with refined grain sizes. The composite with 1 vol% SiC optimized the combination of ultimate tensile strength and ductility, which is attributed to grain-boundary strengthening, twin boundary strengthening, dispersion strengthening and load-bearing strengthening. Simultaneously, the optimized composite with 1 vol% SiC displayed the best wear friction ability, in which the proper SiC content played a key role in carrying load during friction. • Fe 50 Mn 30 Co 10 Cr 10 with four different SiC contents (0.1, 0.5, 1, and 3 vol%) are prepared by the arc-melting. • SiC particles promote phase transformation from ε to γ, refine the grain sizes and decrease the number of ε variants. • Fe 49 Mn 30 Co 10 Cr 10 SiC 1 composite optimizes the combination of ultimate tensile strength and ductility. • Fe 49 Mn 30 Co 10 Cr 10 SiC 1 composite displays the best wear friction ability.

An experimentally driven high-throughput approach to design refractory high-entropy alloys

High-entropy alloy (HEA) design strategies have been limited to theoretical/computational approaches due to their compositional complexity and extremely large compositional parameter space. In this work, we developed an experimentally driven, high-throughput, HEA design approach using a physical vapor deposition (PVD) technique and coupled it with nanomechanical testing to accelerate material design for structural applications. The PVD technique enabled the formation of a compositional gradient across a thin-film sample. Specifically, a 10 cm wafer was used to manufacture a continuous set of 80 HEA compositions within the Nb-Ti-V-Zr family using a single deposition cycle. By using the solid-solution strengthening theory and estimated parameter properties, the strength and ductility of these HEA compositions were quantitatively determined/predicted and then experimentally verified by nano-indentation hardness test. Consequently, 7 refractory HEA compositions were successfully down-selected, which has a high propensity to have a balanced mechanical property.