Tailoring nanostructures and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy using thermo-mechanical processing

Wani, I. S.; Bhattacharjee, Tilak; Sheikh, Saad Ahmed; Bhattacharjee, P.P.; Guo, Sheng; Tsuji, Nobuhiro

doi:10.1016/j.msea.2016.08.048

Cited by 299 publications

(88 citation statements)

References 47 publications

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“…The resulting yield strength of the alloys are 770 MPa for Al 0.7 CoCrFeNi alloy, 740 MPa for FeMnNiAl alloy and 545 MPa for AlCoCrFeNi 2.1 alloy in the as processed condition. While higher yield strengths, as high as 1500 MPa have been reported for the AlCoCrFeNi 2.1 eutectic HEA, these values correspond to heavily cold-rolled (90%) conditions of the eutectic microstructure 42 , resulting in a breakdown of the lamellar morphology and also introduces a high density of dislocations into the phases. Hence, these values cannot be compared with the yield strength of the nano-lamellar eutectoid microstructure present in case of the CRSA600 condition of the Al 0.3 CoFeNi alloy, discussed in this paper.…”

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confidence: 78%

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Dasari

Gwalani

Jagetia

et al. 2020

Sci Rep

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this paper reports a novel eutectoid nano-lamellar (fcc + L1 2 )/(Bcc + B2) microstructure that has been discovered in a relatively simple Al 0.3 cofeni high entropy alloy (HeA) or complex concentrated alloy (CCA). This novel eutectoid nano-lamellar microstructure presumably results from the complex interplay between Al-mediated lattice distortion (due to its larger atomic radius) in a face-centered cubic (FCC) CoFeNi solid solution, and a chemical ordering tendency leading to precipitation of ordered phases such as L1 2 and B2. This eutectoid microstructure is a result of solid-state decomposition of the FCC matrix and therefore distinct from the commonly reported eutectic microstructure in HEAs which results from solidification. This novel nano-lamellar microstructure exhibits a tensile yield strength of 1074 MPa with a reasonable ductility of 8%. The same alloy can be tuned to form a more damagetolerant fcc + B2 microstructure, retaining high tensile yield stress (~900 MPa) with appreciable tensile ductility (>20%), via annealing at 700 °C. Such tunability of microstructures with dramatically different mechanical properties can be effectively engineered in the same CCA, by exploiting the complex interplay between ordering tendencies and lattice distortion.High entropy alloys (HEAs), also referred to as complex concentrated alloys (CCAs) or multi-principal element alloys (MPEAs), offer the ability to design novel microstructures that have not been possible with conventional alloys. In recent times, there has been a rapid increase in papers reporting such novel microstructures with excellent mechanical properties 1-7 . However, there are still many unanswered questions related to the influence of composition and processing on the phase stability, transformation pathways, and microstructural evolution in these complex alloys. In an effort to understand solid solution strengthening in HEAs, the room temperature and high temperature tensile properties of solutionized ternary and quaternary subsets of CoCrFeNiMn (Cantor alloy), CoCrFeNi, CoFeNi, CoCrNi etc. were studied by Wu et al. 8 . They reported that yield strength may not be necessarily a simple function of number of elements but it is a complex relation. Among the systems investigated, CoCrNi had the highest yield strengths overall, at tested temperatures. Since then, numerous investigations have been carried out on this alloy to understand its mechanical behavior 9,10 . Their work also shows that FCC single phase solid solutions in HEAs perform better than conventional FCC single phase alloys and thus strengthening the single phase HEAs with precipitation is anticipated to produce alloys with excellent mechanical properties.Addition of Al to 3d transition element-based face-centered cubic (FCC) high entropy alloys (HEAs), typically containing the elements Co, Cr, Fe, and Ni, results in substantial changes in their microstructure and mechanical properties. This is due to the tendency of Al to effectively introduce an ordering tendency within the FCC matrix, f...

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confidence: 78%

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Dasari

Gwalani

Jagetia

et al. 2020

Sci Rep

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“…Zoomed in view near the B2 phase ( Fig. 7(b)) showed high density of nano-sized precipitates that were previously identified as Cr-rich with disordered BCC structure 19,23 . The average size of the precipitates was about 20 nm.…”

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confidence: 86%

Small-scale mechanical behavior of a eutectic high entropy alloy

Muskeri

Hasannaeimi

Salloom

et al. 2020

Sci Rep

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eutectic high entropy alloys, with lamellar arrangement of solid solution phases, represent a new paradigm for simultaneously achieving high strength and ductility, thereby circumventing this wellknown trade-off in conventional alloys. However, dynamic strengthening mechanisms and phaseboundary interactions during external loading remain unclear for these eutectic systems. In this study, small-scale mechanical behavior was evaluated for Alcocrfeni 2.1 eutectic high entropy alloy, consisting of a lamellar arrangement of L1 2 and B2 solid-solution phases. The ultimate tensile strength was 1165 MPa with ductility of ~18% and ultimate compressive strength was 1863 MPa with a total compressive fracture strain of ~34%. Dual mode fracture was observed with ductile failure for L1 2 phase and brittle mode for B2 phase. Phase-specific mechanical tests using nano-indentation and micro-pillar compression showed higher hardness and strength and larger strain rate sensitivity for B2 compared with L1 2. Micro-pillars on B2 phase deformed by plastic barreling while L1 2 micro-pillars showed high density of slip steps due to activation of more slip systems and homogenous plastic flow. Mixed micropillars containing both the phases exhibited dual yielding behavior while the interface between L1 2 and B2 was well preserved without any sign of separation or cracking. Phase-specific friction analysis revealed higher coefficient of friction for B2 compared to L1 2. These results will pave the way for fundamental understanding of phase-specific contribution to bulk mechanical response of concentrated alloys and help in designing structural materials with high fracture toughness. Multi-principal element alloys (MPEAs), also known as high entropy alloys (HEAs), offer a new paradigm in structural alloy design and development owing to their appealing physical and mechanical properties such as high fracture toughness, good wear and fatigue resistance, high strength and good elevated temperature properties 1-3. Several HEA systems have been reported with a single-phase face center cubic (FCC) or body center cubic (BCC) structure 4-6. To concurrently achieve good ductility of FCC HEAs along with high strength of BCC HEAs, eutectic high entropy alloys (EHEAs) have recently been developed to overcome the limitations of single-phase HEAs 7. EHEAs typically consist of a mixture of two solid-solution phases in the form of lamellae or rod-like dispersions in a matrix. To date, several EHEAs have been reported with excellent combination of high strength and ductility including CoFeNi 1.

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“…Additionally, the properties of HEAs can be significantly improved by thermomechanical processing which makes these alloys immensely suitable for the demanding applications as reported by Wani et al [4]. According to the recent investigations on the eutectic AlCoCrFeNi 2.1 high-entropy alloy [5,6], ultimate tensile strength values exceeding 1000 MPa were obtained along with 10% ductility via rolling the cast samples up to 90% reduction followed by annealing at 1200°C.…”

Section: Introductionmentioning

confidence: 98%

Effect of Heat Treatment and Titanium Addition on the Microstructure and Mechanical Properties of Cast Fe₃₁Mn₂₈ Ni₁₅Al_24.5Ti_x High-Entropy Alloys

El‐Hadad

Ibrahim

Mourad

2019

Advances in Materials Science and Engineering

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High-entropy alloys (HEAs) are multiprincipal element alloys with controllable properties. Studying the mechanical properties of these alloys and relating them to their microstructures is of interest. In the current investigation, Fe31Mn28 Ni15Al24.5Tix high-entropy alloys with Ti content (0–3 wt.%) were prepared by casting in an induction furnace. Different heat treatments were applied, and the microstructure and hardness of the cast samples were studied. It was observed that addition of up to 3.0 wt.% Ti significantly increases the hardness of the alloy from 300 to 500 (Hv) by the combined effect of solid solution strengthening and via decreasing lamellar spacing. Heat treatment at 900°C for 10 h enhanced the hardness at lower Ti percentages (0.0–0.8 wt.%) by decreasing the lamellar spacing, while no change was observed at higher Ti content. It was also observed that extending the treatment time to 20 h affected negatively the hardness of the alloy. Concluding, HEAs can achieve high hardness using low-cost principle elements with minor alloying additives compared to the other traditional alloys.

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Tailoring nanostructures and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy using thermo-mechanical processing

Cited by 299 publications

References 47 publications

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Small-scale mechanical behavior of a eutectic high entropy alloy

Effect of Heat Treatment and Titanium Addition on the Microstructure and Mechanical Properties of Cast Fe₃₁Mn₂₈ Ni₁₅Al_24.5Ti_x High-Entropy Alloys

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Tailoring nanostructures and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy using thermo-mechanical processing

Cited by 299 publications

References 47 publications

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

Small-scale mechanical behavior of a eutectic high entropy alloy

Effect of Heat Treatment and Titanium Addition on the Microstructure and Mechanical Properties of Cast Fe31Mn28 Ni15Al24.5Tix High-Entropy Alloys

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Product

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Effect of Heat Treatment and Titanium Addition on the Microstructure and Mechanical Properties of Cast Fe₃₁Mn₂₈ Ni₁₅Al_24.5Ti_x High-Entropy Alloys