Optimizing the coupled effects of Hall-Petch and precipitation strengthening in a Al 0.3 CoCrFeNi high entropy alloy

Gwalani, Bharat; Soni, Vishal; Lee, Michael; Mantri, S.A.; Ren, Yang; Banerjee, R.

doi:10.1016/j.matdes.2017.02.072

Cited by 340 publications

(123 citation statements)

References 24 publications

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“…This problem is typical of single fcc phase HEAs based on 3d transition metals [3,26]. A proper tailoring of the chemical composition along with microstructure modification using thermal/thermomechanical treatment resulted in alloys, which showed a significant increment in strength without sacrifice in ductility due to the formation of fine fcc grains and/or nanoscale precipitates of second phase(s) [10,14,[27][28][29][30][31][32][33][34]. The most significant strengthening was found to be induced by nanoscale precipitates (e.g.…”

Section: Introductionmentioning

confidence: 99%

Recrystallized microstructures and mechanical properties of a C-containing CoCrFeNiMn-type high-entropy alloy

Klimova

Shaysultanov

Chernichenko

et al. 2019

Materials Science and Engineering: A

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The effect of cold rolling to 80% thickness reduction and annealing at 973-1373 K for 1 h on the microstructure and mechanical properties of a C-containing CoCrFeNiMn high-entropy alloy was studied. Cold rolling significantly strengthened the alloy to the yield strength of 1310 MPa. Annealing at 973 K or 1073 K resulted in incomplete recrystallization of an fcc matrix and M 23 C 6-type carbide precipitations aligned with highly elongated grains/subgrains. Complete recrystallization occurred during annealing at 1173 − 1373 K. The ordered arrangement of the carbides was not observed after annealing at 1273 K or 1373 K. The volume fraction of carbides decreased with increasing the annealing temperature that can be reasonably described by a Thermo-Calc prediction. The coarsening behavior of the microstructure constituents was studied during isothermal annealing at 1173 K for 1-50 h. It was found that the grain growth and the particle coarsening can be expressed by power law functions of annealing time with grain/particle size exponents of about 2 and 3, respectively. An increase in the annealing temperature from 973 K to 1373 K led to a gradual softening of the alloy; the yield strength decreased from 870 MPa to 320 MPa, whereas total elongation increased from 24% to 47%, respectively. Contributions of various strengthening mechanisms into the overall strength of the alloy were discussed.

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Section: Introductionmentioning

confidence: 99%

Recrystallized microstructures and mechanical properties of a C-containing CoCrFeNiMn-type high-entropy alloy

Klimova

Shaysultanov

Chernichenko

et al. 2019

Materials Science and Engineering: A

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“…Larger Al contents eventually de-stabilize the FCC lattice and result in the formation of a BCC lattice, coupled with ordering to form B2 or related phases in the HEA. Based on this idea, many groups have attempted to develop precipitation strengthened FCC-based HEAs [12][13][14][15][16][17][18][19] . Additionally, the alloying of these FCC-based HEAs…”

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confidence: 99%

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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“…Then using the data in Table 1, the increment of dislocation hardening (∆σ D ) is about 259.0 MPa calculated by Equation (7). The back stress σ b is caused by two incompatibility le- , where d is the mean grain size (~21.6 µm), k = 824 MPa μm is the Hall-Petch slope [51].…”

Section: Strengthening Mechanisms and Evaluationmentioning

confidence: 99%

“…Consequently, the long-range internal stress named as intergranular back stress (∆σ inter ) is induced. At the yield point, the ∆σ inter can be obtained as about 216.4 MPa using ∆σ inter = σ y -σ 0 − ∆σ p − ∆σ D , where σ y is the yield stress and equals 775 MPa, and the friction stress σ 0 equals 95 MPa[51]. In fact, the increased strength from the ∆σ inter is similar to the GB hardening effect (∆σ G ).…”

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confidence: 99%

Tailored microstructures and strengthening mechanisms in an additively manufactured dual-phase high-entropy alloy via selective laser melting

Luo

Wang

2020

Sci. China Mater.

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Dual-phase high-entropy alloys (DP-HEAs) with excellent strength-ductility combinations have attracted scientific interests. In the present study, the microstructures of AlCrCuFeNi 3.0 DP-HEA fabricated via selective laser melting (SLM) are rationally adjusted and controlled. The mechanisms engendering the hierarchical microstructures are revealed. It is found that the AlCrCuFeNi 3.0 fabricated by SLM at the scanning speed of 400 mm s −1 falls into the eutectic coupled zone, and increasing the scanning speed will make this composition deviate away from the eutectic coupled zone due to the increased cooling rate. The enrichment of Cr and Fe solutes with large growth restriction values ahead of the solid/ liquid interface can develop a constitutional supercooling zone, thus facilitating the heterogeneous nucleation and nearequiaxed grain formation. The synergy of the near-eutectic DP nano-structures and near-equiaxed grains instead of columnar ones effectively suppresses cracking for the as-built DP-HEA.During the tensile deformation, the intergranular back stress hardening similar to the grain-boundary strengthening is discovered. Meanwhile, the near-eutectic microstructures comprised of soft face-centered cubic and hard ordered bodycentered cubic (B2) DP nano-structures lead to plastic strain incompatibility within grains, thus producing the intragranular back stress. The Cr-rich nano-precipitates inside the B2 phase are found to be sheared by dislocation gliding and can complement the back stress. Additionally, multiple strengthening mechanisms are physically evaluated, and the back stress strengthening contributes obviously to the high performances of the as-built DP-HEA.

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Optimizing the coupled effects of Hall-Petch and precipitation strengthening in a Al 0.3 CoCrFeNi high entropy alloy

Cited by 340 publications

References 24 publications

Recrystallized microstructures and mechanical properties of a C-containing CoCrFeNiMn-type high-entropy alloy

Recrystallized microstructures and mechanical properties of a C-containing CoCrFeNiMn-type high-entropy alloy

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

Tailored microstructures and strengthening mechanisms in an additively manufactured dual-phase high-entropy alloy via selective laser melting

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