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High entropy alloys represent a new paradigm of structural alloy design consisting of (near) equal proportions of constituent elements resulting in a number of attractive properties. In particular, eutectic high entropy alloys offer a remarkable combination of high strength and good ductility from the synergistic contribution of each phase in the e...
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In this paper, the recently developed three-scale crystal plasticity model is applied to simulate microstructural evolution of austenitic and ferritic stainless steels subjected to large plastic strains. It is shown that the model is able to correctly predict both texture and misorientation angle distributions in the materials studied. Moreover, it...
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... Even though the selective dissolution of BCC phase was achieved and EHEA AlCoCrFeNi 2.1 exhibited a lower pitting potential than SS304, one study still showed that EHEA has the same level of corrosion current as stainless steel 304 (SS304) in 1% NaCl solution during the PD test [24]. Another study compared the electrochemical behaviors of OCP, EIS, and PD, and AlCoCrFeNi 2.1 was found to have comparable corrosion resistance as SS304 in 3.5% NaCl solution [53]. One study even found that with proper fabricating method (gas atomization was applied), AlCoCrFeNi 2.1 showed superior corrosion resistance than SS304 in 10% HCl and 3.5% NaCl solutions [54]. ...
High-entropy alloys (HEAs) are emerging as a new family of alloys with equal/near-equal amounts of constituting elements and outstanding properties. In particular, eutectic high-entropy alloys (EHEAs) with alternate lamella phases possess both high strength and ductility, offering the advantage of conquering the strength–ductility trade-off that could hardly be achieved by conventional alloys. While the mechanical behavior of EHEAs has been widely studied, the corrosion behavior is still not fully understood. Furthermore, the environment-induced degradation could largely decide the service life of EHEA as engineering alloys, and the eutectic structure may have a special influence on the corrosion process. This article systematically reviews the corrosion studies of EHEAs by pointing out the structural features of EHEAs, summarizing the general corrosion issues for EHEAs and identifying the specific corrosion performance of different EHEA systems. It is found that EHEAs feature micro-galvanic corrosion due to their eutectic crystal structure, and such a corrosion mode is further affected by testing time, heat treatment, temperature, and applied potential. All the corrosion-affecting factors are summarized, and future research directions are suggested, aiming at ensuring the wide engineering application of EHEAs with both high strength–ductility and corrosion resistance.
... Al 0.1 CoCrFeNi showed superior wear resistance over CoCrFeMnNi in both dry and corrosive environments due to its increased hardness, which resulted in enhanced abrasion resistance. Hasannaeimi et al. [166] studied the corrosion and wear resistance of arc-melted AlCoCr-FeNi 2.1 eutectic HEA composed of FCC (L1 2 ) and BCC (B2) phases. During the sliding, the soft L1 2 phase deformed more readily than the BCC (B2) phase. ...
... 24. Wear mechanisms of Al-Cr-Co-Fe-Ni based HEAs manufactured by different methods [43,138,150,165,166,168,175,182,190,192,211,218,221]. ...
... only slip deformation was triggered [166]. The experiment temperature also had a great impact on evolved wear mechanisms during the wear of Al-Cr-Co-Fe-Ni HEAs fabricated by the arc melting method [182,190,192]. ...
... Dual-phase steels have been reported to have excellent corrosion resistance and a good combination of strength and ductility [29][30][31][32][33][34][35]. To explain the effect of eutectic microstructure on the local electrochemical activity, Scanning Kelvin Probe (SKP) analysis was utilized to measure the relative electron work function [27,36,37]. Our findings pave the way for further research on molten salt corrosion behavior of dual-phase alloys over a wide range of temperature for potential use in concentrating solar power systems. ...
... Reference source not found.f). Previous studies suggest that the relative chemistry difference and phase volume fraction (FCC:BCC) determine the degree of degree of galvanic coupling in dual-phase alloys [27,[42][43][44][45]. At 650 °C, duplex steel has been reported to show chloride-induced severe corrosion due to preferential attack of its ferrite phase [46]. ...
... At 650 • C, uniform pitting was observed all over the surface for AlCoCrFeNi 2.1 (Figure 5e) in contrast to severe material loss from selective removal of the BCC (α-Ferrite) phase in DS2205 (Figure 5f). Previous studies suggest that the relative chemistry difference and phase volume fraction (FCC:BCC) determine the degree of degree of galvanic coupling in dualphase alloys [27,[42][43][44][45]. At 650 • C, duplex steel has been reported to show chloride-induced severe corrosion due to preferential attack of its ferrite phase [46]. ...
Dual-phase high entropy alloys have recently attracted widespread attention as advanced structural materials due to their unique microstructure, excellent mechanical properties, and corrosion resistance. However, their molten salt corrosion behavior has not been reported, which is critical in evaluating their application merit in the areas of concentrating solar power and nuclear energy. Here, the molten salt corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was evaluated in molten NaCl-KCl-MgCl2 salt at 450 °C and 650 °C in comparison to conventional duplex stainless steel 2205 (DS2205). The EHEA showed a significantly lower corrosion rate of ~1 mm/year at 450 °C compared to ~8 mm/year for DS2205. Similarly, EHEA showed a lower corrosion rate of ~9 mm/year at 650 °C compared to ~20 mm/year for DS2205. There was selective dissolution of the body-centered cubic phase in both the alloys, B2 in AlCoCrFeNi2.1 and α-Ferrite in DS2205. This was attributed to micro-galvanic coupling between the two phases in each alloy that was measured in terms of Volta potential difference using a scanning kelvin probe. Additionally, the work function increased with increasing temperature for AlCoCrFeNi2.1, indicating that the FCC-L12 phase acted as a barrier against further oxidation and protected the underlying BCC-B2 phase with enrichment of noble elements in the protective surface layer.
... construction of structural alloys, having five or more elements in equimolar or near-equimolar proportions. [13][14][15][16] Phase formation is governed more by the configurational entropy than by the mixing entropy, which causes HEAs generally to form simple solid solutions with face-centered-cubic (FCC), or body-centered-cubic (BCC), or hexagonal-close-packed (HCP) structures, rather than brittle intermetallics. 13,14,[17][18][19][20][21][22] HEAs, especially FCC HEAs, have recently come to light as a viable contender for advanced structural applications due to their promising mechanical properties, such as excellent tensile strength, outstanding fatigue life, high fracture toughness at cryogenic temperatures, good ductility, and work hardenability, among other desirable attributes stemming from the multiple principal element approach. ...
High-entropy alloys (HEAs), recently emerging alloys with numerous excellent mechanical performances, may have a wide application prospect in impact engineering. The ballistic impact response of Fe 40 Mn 20 Cr 20 Ni 20 HEA was investigated under various loading conditions. Ballistic impact tests with spherical projectiles and 87 type 5.8 mm small caliber bullets (DBP87 bullets) were conducted on 10 mm thick Fe 40 Mn 20 Cr 20 Ni 20 HEA plates with varying impact velocities, compared with 20Mn23AlV steel (high manganese low magnetic steel). The relationship between microstructural details and aspects of ballistic behavior governing performance was established through experimental explorations and theoretical models. According to the findings, dense dislocation structures led to distinguishing work hardening in the HEA, and the strain-hardening capacity of the HEA enhanced dramatically with increasing strain rate under dynamic tension. Meanwhile, under 500 m/s impact velocity, twinning and microbanding had outstanding strain-hardening capabilities for the current HEA, and the cooperation of the dislocation slip and stacking faults was critical for strain hardening in the HEA when the impact velocity was increased to [Formula: see text], whereas only a small amount of dislocation sliding and twinning occurred during the dynamic deformation process of 20Mn23AlV steel at different impact velocities. These findings demonstrated that the outstanding strain-hardening capabilities of Fe 40 Mn 20 Cr 20 Ni 20 HEA made it a promising candidate for ballistic impact engineering compared with 20Mn23AlV steel.
... The large fluctuation in the friction coefficient of the two alloys is due to the difference in the hardness of the two phases. Hasannaeimi et al. [26] measured the friction coefficients of the B2 and L12 phases in AlCoCrFeNi2.1 using micro-indentation, and the average friction coefficient was about 0.87 for the high hardness B2 phase and about 0.82 for the low hardness L12 phase. From Figure 5b, it can be concluded that the wear weight loss of the two high-entropy alloys before and after laser surface remelting treatment is 0.0231 mm 3 and 0.0179 mm 3 after 30 min reciprocal friction, respectively. ...
In this study, laser surface remelting of an AlCoCrFeNi2.1 high-entropy alloy was performed using a Yb:YAG laser. The effects of laser surface remelting on the phase structure, microstructure, Vickers hardness, frictional wear properties, and corrosion resistance of the high-entropy alloy were investigated. The remelted layer of the AlCoCrFeNi2.1 high-entropy alloy was produced by remelting at 750 W laser power and formed a good metallurgical bond with the substrate. The X-ray diffraction results showed that the 750 W remelted layer consisted of face-centered cubic and body-centered cubic phases, which were consistent with the phases of the as-cast AlCoCrFeNi2.1 high-entropy alloy, and a new phase was not generated within the remelted layer. Laser surface remelting is very effective in refining the lamellar structure, and the 750 W remelted layer shows a finer lamellar structure compared to the matrix. The surface hardness and wear resistance of the AlCoCrFeNi2.1 high-entropy alloy were substantially improved after laser surface remelting. In a 3.5 wt.% NaCl solution, the laser-remelted surface had a larger self-corrosion potential and smaller self-corrosion current density, and the corrosion resistance was better than that of the as-cast high-entropy alloy.
... The equivalent circuits consisting of resistors and capacitors are shown in Fig. 3(c & d), which simulated the electrochemical behavior of the surface-solution interface. A constant phase element (CPE) was used to account for the non-ideal behavior of the double layer, like surface roughness, adsorption effects, and surface inhomogeneities, instead of pure capacitance [48,49]. CPE impedance may be represented as follows [50,51]: ...
... Scanning Kelvin Probe (SKP) was used for measuring the relative SKP potential with respect to tungsten probe and correlating electronic structure to the corrosion resistance of the amorphous alloys. SKP potential has been correlated with electron work function (EWF) to explain the corrosion behavior in earlier studies [48,66]. A nobler surface is associated with a higher work function, which is directly related to the ease of electron removal [67]. ...
Effect of chemistry change on corrosion mechanisms and passive film characteristics of model Ni-P and Co-P metallic glass coatings on mild steel was studied because of their simple chemistry and widespread use. Increase in phosphorus content led to improved corrosion resistance. Results indicated the presence of hypophosphite and phosphate anions on the corroded surfaces. Enrichment of phosphorus in the passive layer was observed, which likely promoted the restoration of the protective hypophosphite anion layer during dissolution. A correlation between electronic structure and corrosion resistance was established, with relative work function increasing with increase in phosphorus content.
... correlating electronic structure to the corrosion resistance of the amorphous alloys. V SKP is proportional to electron work function (EWF), which has been correlated with corrosion behavior in earlier studies [45,57]. A nobler surface is associated with a higher work function, which is directly related to the ease of electron removal [58]. ...
... The equivalent circuits consisting of resistors and capacitors are shown inFigure 4cand 4d, which simulated the electrochemical behavior of the surface-solution interface. Instead of an ideal double-layer capacitance (C), a constant phase element (CPE) was used to account for the non-ideal behavior of the double layer, like surface roughness, adsorption effects, and surface inhomogeneities[45,46]. The equivalent circuit(Figure 4c) of electrodeposited Ni 90 P 10 , Co 90 P 10 , pure Ni, and MS 1008 contains elements corresponding to the solution resistance (R s ), pore capacitance (CPE pore ), pore resistance (R pore ), double-layer capacitance (CPE dl ), and charge transfer resistance (R ct ). ...
... Complex concentrated alloys (CCAs), also known as high entropy alloys (HEAs), represent a new paradigm in structural alloy design containing five or more elements in equi-molar or near equi-molar proportions [19][20][21][22]. This fundamentally shifts the focus to central region of the multi-component phase space as opposed to the conventional approach of a single dominant element. ...
... This fundamentally shifts the focus to central region of the multi-component phase space as opposed to the conventional approach of a single dominant element. Complex concentrated alloys have attracted widespread interest in advanced structural applications due to their exceptional mechanical properties such as high strength, high fracture toughness, good ductility and work hardenability among other desirable attributes resulting from the multiple principal element approach [19][20][21][22]. They offer unique opportunity in terms of tunability of microstructure by selection of appropriate constituent elements and thermo-mechanical processing [19][20][21][22]. ...
... Complex concentrated alloys have attracted widespread interest in advanced structural applications due to their exceptional mechanical properties such as high strength, high fracture toughness, good ductility and work hardenability among other desirable attributes resulting from the multiple principal element approach [19][20][21][22]. They offer unique opportunity in terms of tunability of microstructure by selection of appropriate constituent elements and thermo-mechanical processing [19][20][21][22]. In particular, the Al x CoCrFeNi (variable Al content represented by x) high entropy alloy system has been widely studied in terms of their microstructure, phase stability and associated mechanical properties [23][24][25][26]. ...
The performance of complex concentrated alloys (or high entropy alloys) with widely varying microstructure is evaluated by ballistically impacting targets with spheres fired at normal incidence. By changing alloy composition in the Al-Co-Cr-Fe-Ni multi-principal system, the variation in microstructure included single-phase equiaxed grains, single-phase with bimodal grain-size distribution, and eutectic two-phase lamellar microstructure. Rigorous characterization in the form of bulk mechanical testing, scanning electron microscopy, and spatially resolved nano-indentation on initial and ballistically impacted plates was used to connect microstructural details to aspects of ballistic behavior governing performance. Based on the results, it was shown that although the addition of a harder secondary phase improves strength, cracks that initiate and propagate within the harder phase and ultimately across the target plate drastically reduce the ballistic performance of the two-phase material. The single-phase alloy with bimodal grain-size distribution exhibited superior ballistic performance compared to the other high entropy alloys, although none of these materials exceeded the performance of conventional rolled homogeneous armor steel. These results pave the way for development of high-performance concentrated alloys for ballistic applications by appropriate microstructural design.
... Nucleation of multiple shear bands in the mixed pillars and their propagation in different directions might have resulted in accommodation of higher amount of strain before failure providing a pathway for J o u r n a l P r e -p r o o f design of composite materials with ultra-high toughness. Significant toughness enhancement, plasticity accommodation, and surface degradation resistance has been reported recently in the case of dual-phase eutectic high entropy alloys [25][26][27], dual-phase bimodal steels [28,29], and other multi-phase systems [30]. ...
Bulk metallic glass matrix composites represent a unique microstructural design strategy for overcoming the strength/ductility trade-off in structural alloys. Site-specific mechanical behavior of a Ti-based bulk metallic glass composite was evaluated at microstructural length-scale. The micro-pillars on the amorphous matrix showed on average a yield point of 1.9 GPa followed by serrated plastic deformation characteristic of shear banding. In contrast, micro-pillars on the crystalline dendritic phase showed a much lower yield strength of 0.72 GPa on average for the four different crystallographic orientations chosen, smooth plastic flow with no recognizable load burst, and stable strain-hardening after yield point. A number of micro-pillars were made at the interface between the glassy matrix and the crystalline dendrite. The mixed micro-pillars showed homogeneous deformation and greater plasticity which was attributed to their smaller stored elastic energy. Shear bands initiated in the amorphous matrix were arrested by the crystalline dendrite, which accommodated plasticity through slip bands and dislocations pile-ups. The interface remained intact after plastic deformation, with no observable signs of devitrification in the amorphous phase.
... These results justify measurement of mechanochemical degradation with electrochemical response in vivo. work function or potential distribution map of metal/alloy surfaces (Hasannaeimi et al., 2019). Work function is defined as the minimum energy needed to remove electrons from a material's surface (Hasannaeimi & Mukherjee, 2019b), and therefore, corrosion is closely related to a material's work function (Hasannaeimi et al., 2019). ...
... work function or potential distribution map of metal/alloy surfaces (Hasannaeimi et al., 2019). Work function is defined as the minimum energy needed to remove electrons from a material's surface (Hasannaeimi & Mukherjee, 2019b), and therefore, corrosion is closely related to a material's work function (Hasannaeimi et al., 2019). Similar to SKP, the potential distribution over a material's surface is imaged in SVET and helps to detect active sites that are likely to initiate localized corrosion (Hasannaeimi & Mukherjee, 2019a). ...
... SKP analysis showed relatively lower work function and thus higher electro-positivity for the B2 phase as compared with L12 (Figure 2c), further confirming preferential corrosion. Electron release may be easier for B2 phase with lower work function (Hasannaeimi et al., 2019) and thus preferential removal as shown in Figure 2b. The alloys with lower work function showed higher catalytic activity due to the easier charge transfer on the surface (Hasannaeimi & Mukherjee, 2019b). ...
In‐vivo monitoring of biomedical implants to detect early stages of failure is currently unavailable. State of the art imaging techniques do not provide information about small‐scale localized changes in the implant and surrounding environment, which are key to early detection of failure. Here, we discuss different electrochemical responses of implants during degradation which may be utilized to develop biosensors to monitor implant degradation in‐vivo. This review is focused on identifying the need, potential measurement techniques, and degradation response obtained from sensors based on electrochemical signature of biomedical implants. Benefits of designing these novel sensors include continuous monitoring, early failure detection, reduced post‐surgery, and prevention of catastrophic failure from implant degradation.
