Retardation of the σ phase formation in the AlCoCrFeNi multi-component alloy

Meshi, Louisa; Linden, Yatir; Munitz, A.; Salhov, S.; Pinkas, Malki

doi:10.1016/j.matchar.2018.12.010

Cited by 35 publications

(15 citation statements)

References 21 publications

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“…Although the amount of bcc * increased with increasing Al content, the general appearance of this B2/A2 phase mixture remained unchanged. This is in good agreement with most of the experimental data in literature derived from melting and casting (Wang et al, 2012;Munitz et al, 2016;Lim et al, 2017;Meshi et al, 2019) as well as the additive manufacturing fabrication route (Kunce et al, 2015;Li et al, 2018;Niu et al, 2019;Karlsson et al, 2019b) of Al x CoCrFeNi alloys. In accordance with the interpretation of Li et al (2018) and Karlsson et al (2019b) the very fine-scaled dual B2/A2 phase arrangement is regarded as the result of a spinodal decomposition.…”

Section: Discussionsupporting

confidence: 90%

“…In accordance with the interpretation of Li et al (2018) and Karlsson et al (2019b) the very fine-scaled dual B2/A2 phase arrangement is regarded as the result of a spinodal decomposition. Previous works performed on equiatomic AlCoCrFeNi or near equiatomic Al 0.9 CoCrFeNi showed that these alloys underwent the following transformation of B2 + A2 → B2 + fcc (A1) + σ during heat treatment at 1123 K (Wang et al, 2014;Meshi et al, 2019). The formation of the brittle σphase in Al x CoCrFeNi alloys at intermediate temperatures has been regarded as a major drawback for industrial applications since it probably limits the operating temperatures to 500 • C. According to CALPHAD calculations and the literature discussed in the introduction the avoidance of σ-phase formation during homogenization treatments require temperatures above approximately 1250 K at which the σ-phase dissolves leading to a mixture of A2 + B2 + fcc phases (Munitz et al, 2016;Butler and Weaver, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…With the addition of Al (0 ≤ x ≤ 1.2) and alongside the transition from fcc to bcc microstructure, the hardness of the alloy increases from about 120 HV to about 500 HV (Kao et al, 2009). Different studies indicate that the as cast microstructures of the Al-rich (x ≥ 1) alloys are not stable at elevated temperatures (Wang et al, 2014;Munitz et al, 2016;Meshi et al, 2019). At temperatures above 923 K the dual A2 + B2 bcc structure decomposes into B2 + fcc + σ phase.…”

Section: Introductionmentioning

confidence: 99%

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Alloy Design and Microstructure Evolution in the AlxCoCrFeNi Alloy System Synthesized by Laser Metal Deposition

et al. 2020

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In this contribution the Al x CoCrFeNi alloy system is explored thoroughly over a wide compositional range of x = 0.2 to 1.5 (5 to 30 at% Al). For this alloy system compositional gradient structures were produced by laser metal deposition of pre-alloyed CoCrFeNi and elemental Al powders using an in-house developed coaxial cladding system COAXpowerline. The evolution of the microstructure with increasing Al content was analyzed in the as built as well as the homogenized condition (1350 K for 20 h). Metallographic cross sections were prepared and thoroughly analyzed by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscattered diffraction. Additionally, the evolution of the sample hardness with increasing Al contents was determined for both sample conditions. In the Al x CoCrFeNi alloy system the lattice structure as well as the sample hardness can easily be adjusted by the variation of Al. With increasing Al content a phase transition from a solid solution fcc phase toward a multiphase bcc microstructure consisting of a Fe and Cr rich solid solution bcc phase and an ordered Al and Ni rich bcc B2 phase can be observed. This is combined with an increase in sample hardness from around 200 HV up to around 500 HV in the as built condition. The compositional regions of the phase transitions for both sample conditions were compared to ab initio thermodynamic calculations done using a CALPHAD approach. For the as built condition a strong deviation from the calculated transition regime could be observed. After homogenization the experimental and calculated data are in good agreement.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alloy Design and Microstructure Evolution in the AlxCoCrFeNi Alloy System Synthesized by Laser Metal Deposition

et al. 2020

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“…As-cast AlxCoCrFeNi alloys commonly consist of FCC dendrites and a BCC interdendritic phase, depending on the Al content: only the FCC phase was obtained for x = 0-0.3, a FCC+BCC mixture for x = 0.5-0.8, and BCC alone for x = 0.9-3.0 8,9 . At temperatures above 873 K, the as-cast equiatomic AlCoCrFeNi BCC phase transforms into FCC, with simultaneous precipitation of B2 and s phase inclusions 10 . A mechanically synthesized AlCoCrFeNi BCC phase transformed into a partially disordered B2 phase after 1 h annealing at 1073 K 11,12 .…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of Medium- and High-Entropy Alloys of 3d-Transition Metals

Fourmont

Рогачев

Gallet

et al. 2021

J. Phase Equilib. Diffus.

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A family of High-Entropy Alloys (HEA) composed of 3d-transitional metals is attracting great interest due to the mechanical, magnetic and electrical properties that are valuable in the development of advanced structural and functional materials. In this work, we studied X-CoCrFeNi HEAs, where X = Al, Ti, or Cu, produced by mechanical alloying by means of highenergy ball milling. Powder mixture composed of elemental metal powders transforms in a homogeneous alloy (super-saturated solid solution) due to the intense diffusion which takes place in the course of friction and shear deformation of the metal particles during the mechanical alloying. The thermal stability of the HEA phases was experimentally studied in the range 873 K -1273 K using high-temperature X-ray diffraction and compared with the results of thermodynamic calculations (Calphad).

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“…[6]. Alongside its many advantages, this alloy has disadvantages such as the formation of the σ phase, which embrittles the alloy at high temperatures [7]. In order to promote the use of the AlCoCrFeNi-based alloys in the industry and perform rational design of new high entropy alloys, the role of each element in the original AlCoCrFeNi quinary alloy must be defined.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Role of the Constituting Elements of the AlCoCrFeNi High Entropy Alloy through the Investigation of Quaternary Alloys

Hillel

Natovitz

Salhov³

et al. 2020

Metals

Self Cite

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Quinary AlCoCrFeNi high entropy alloy (HEA) is one of the most studied alloys in the recent decade due to its outstanding properties. However, it is still far from becoming an applicable industrial alloy. To our understanding, in order to promote this, the role of elements, constituting the quinary alloy, needs to be defined. Knowing the role of each element, modification of the quinary alloy toward minimization of its disadvantages will be possible. In the current research, we shed some light on this subject, presenting a thorough investigation of the microstructure (carried out using scanning and transmission electron microscopy) and mechanical properties, performed by microhardness and fractography post small punch test (SPT), of five equiatomic quaternary alloys, constituting the quinary system, namely: CoCrFeNi, AlCoFeNi, AlCoCrNi, AlCoCrFe, and AlCrFeNi. CoCrFeNi (i.e., w/o Al) was found to be Face Centered Cubic (FCC) solid solution, exhibiting relatively low micro-hardness and ductile fracture post SPT measurement. AlCoFeNi (i.e., w/o Cr) was essentially single phase B2. Other alloys had a mixed BCC + B2 dual phase content with variable microstructures and sizes of particles. The fine microstructure of the alloy without Ni implies eutectic solidification or spinodal decomposition. This fine microstructure imposed remarkable high hardness though the alloy was too brittle and unmachinable. Among the BCC/B2 mixture alloys, Fe and Co-less ones resembled the most quinary AlCoCrFeNi in terms of microstructure and mechanical properties.

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Retardation of the σ phase formation in the AlCoCrFeNi multi-component alloy

Cited by 35 publications

References 21 publications

Alloy Design and Microstructure Evolution in the AlxCoCrFeNi Alloy System Synthesized by Laser Metal Deposition

Alloy Design and Microstructure Evolution in the AlxCoCrFeNi Alloy System Synthesized by Laser Metal Deposition

Thermal Stability of Medium- and High-Entropy Alloys of 3d-Transition Metals

Understanding the Role of the Constituting Elements of the AlCoCrFeNi High Entropy Alloy through the Investigation of Quaternary Alloys

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