Processing, alloy composition and phase transition effect on the mechanical and corrosion properties of high entropy alloys: a review

Alaneme, Kenneth Kanayo; Bodunrin, Michael Oluwatosin; Oke, Samuel Ranti

doi:10.1016/j.jmrt.2016.03.004

Cited by 124 publications

(38 citation statements)

References 63 publications

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“…[24][25][26] Among the HEA systems, CoCrFeNi have been extensively investigated over the past 13 years. [1][2][3][4][5][6]27] Cu, Al, and Ti are often added separately or together as minor or equivalent amount in CoCrFeNi system to improve the corrosion and mechanical properties. [13,28,29] With increasing Al or Ti content, the crystallographic structure of the alloys show gradual changes from FCC to FCC þ BCC and finally to fully BCC phases.…”

Section: Introductionmentioning

confidence: 99%

Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy Alloy

2017

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A CoCrCuFeNi high entropy alloy (HEA) is prepared from the high purity elemental Co,Cr, Cu,Fe, and Ni powders by mechanical alloying (MA) at different milling speed (200 or 350 rpm). Mechanically alloyed powder samples are subsequently annealed at different temperatures (300, 500, 700, and 800 C). Microstructures, chemical composition, and phase stability of the powders are studied using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and energy dispersive X-ray spectrometry (EDS). The results show that, a single phase stable FCC solid solution is formed within 5 and 50 h of milling at 350 and 200 rpm, respectively. The single FCC phase is identified to be thermally stable upto 800 C and then it is decomposed into two FCC phases. The second FCC phase is found to be rich in Cu. The precipitation of the Cu rich phase is likely due to the positive enthalpy of mixing of Cu with other alloying elements.

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Section: Introductionmentioning

confidence: 99%

Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy Alloy

2017

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“…The production of HEAs does not require special processing equipment; so, the manufacturing of HEAs can be easily realized with existing technologies and equipment (Tsai et al 2014;Gao et al 2016). Nowadays, the primary method to synthesize HEAs is vacuum arc remelting for bulk cast ingot; mechanical alloying followed by isostatic pressing and surface coating is also possible (Murty et al 2014;Gao et al 2016;Alaneme et al 2016). HEA coatings were mainly produced using fusion-based technologies, such as laser cladding (Alaneme et al 2016;Zhang et al 2017), plasma cladding (Dong et al 2013;Cai et al 2017a, b), plasma spraying Alaneme et al 2016) and magnetron sputtering (Chang 2018;Zhang et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Nowadays, the primary method to synthesize HEAs is vacuum arc remelting for bulk cast ingot; mechanical alloying followed by isostatic pressing and surface coating is also possible (Murty et al 2014;Gao et al 2016;Alaneme et al 2016). HEA coatings were mainly produced using fusion-based technologies, such as laser cladding (Alaneme et al 2016;Zhang et al 2017), plasma cladding (Dong et al 2013;Cai et al 2017a, b), plasma spraying Alaneme et al 2016) and magnetron sputtering (Chang 2018;Zhang et al 2018). However, melting and solidification commonly result in phase transformation and element segregation of the HEA coatings, breaking the nature of HEAs (Cai et al 2017a, b).…”

Section: Introductionmentioning

confidence: 99%

Nanostructured AlNiCoFeCrTi high-entropy coating performed by cold spray

et al. 2020

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In this work, solid-state mechanical alloying (MA) and cold spraying (CS) processes were applied to fabricate powder AlNiCoFeCrTi high-entropy alloy (HEA) and then to produce HE coatings on steel substrate. Shot-time MA for 3 h has been employed to synthesize nanostructured equiatomic AlNiCoFeCrTi HEA of metastable supersaturated substitutional solid solution with bcc crystal structure. Although alloying is not complete at this shot milling time, it goes to completion during thermal annealing to achieve the alloy formation. XRD study on mechanically alloyed high-entropy AlNiCoFeCrTi alloy after thermal annealing at 1200 °C for 1 h revealed the formation of a three-phase structure consisting of ordered bcc phase with fine precipitates of intermetallic σ-phase (FeCr) and titanium carbide TiC. The powder agglomerates resulted from annealing were grinded in a ball mill for 1 h. Nanostructured disordered bcc solid solution, TiC and σ-phases are noticed after milling. Coatings of 450 μm in mean thickness were deposited by the CS process using an air like a working gas, temperature and pressure of 450 °C and 0.9 MPa, respectively. The experimental results confirm that CS process can be used to produce HE coatings with low porosity. As a low-temperature deposition process, CS completely retained the HEA phase composition and nanostructure in the coating without any phase transformation. The AlFeNiCoCrTi HE coatings exhibit 10.3 ± 0.3 GPa in Vickers hardness.

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“…HEA can be produced by many different routes such as liquid processing approaches (e.g., arc melting, Bridgman solidification, atomization and laser cladding), additive manufacturing, mechanical alloying (e.g., powder metallurgy), mixing elements of the vapor state including sputter deposition, atomic layer deposition and vapor phase deposition [ 1 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Welding is a complex process due to the fact that many conditions or factors affect the welding process.…”

Section: Introductionmentioning

confidence: 99%

Welding of High Entropy Alloys—A Review

Guo

Tang

Rothwell

et al. 2019

Entropy

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High-entropy alloy (HEA) offers great flexibility in materials design with 3–5 principal elements and a range of unique advantages such as good microstructure stability, mechanical strength over a broad range of temperatures and corrosion resistance, etc. Welding of high entropy alloy, as a key joining method, is an important emerging area with significant potential impact to future application-oriented research and technological developments in HEAs. The selection of feasible welding processes with optimized parameters is essential to enhance the applications of HEAs. However, the structure of the welded joints varies with material systems, welding methods and parameters. A systemic understanding of the structures and properties of the weldment is directly relevant to the application of HEAs as well as managing the effect of welding on situations such as corrosion that are known to be a service life limiting factor of welded structures in conditions such as marine environments. In this paper, key recent work on welding of HEAs is reviewed in detail focusing on the research of main HEA systems when applying different welding techniques. The experimental details including sample preparation, sample size (thickness) and welding conditions reflecting energy input are summarized and key issues are highlighted. The microstructures and properties of different welding zones, in particular the fusion zone (FZ) and the heat affected zones (HAZ), formed with different welding methods are compared and presented in details and the structure-property relationships are discussed. The work shows that the weldability of HEAs varies with the HEA composition groups and the welding method employed. Arc and laser welding of AlCoCrFeNi HEAs results in lower hardness in the FZ and HAZ and reduced overall strength. Friction stir welding results in higher hardness in the FZ and achieves comparable/higher strength of the welded joints in tensile tests. The welded HEAs are capable of maintaining a reasonable proportion of the ductility. The key structure changes including element distribution, the volume fraction of face centered cubic (FCC) and body centered cubic (BCC) phase as well as reported changes in the lattice constants are summarized and analyzed. Detailed mechanisms governing the mechanical properties including the grain size-property/hardness relationship in the form of Hall–Petch (H–P) effect for both bulk and welded structure of HEAs are compared. Finally, future challenges and main areas to research are highlighted.

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Processing, alloy composition and phase transition effect on the mechanical and corrosion properties of high entropy alloys: a review

Cited by 124 publications

References 63 publications

Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy Alloy

Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy Alloy

Nanostructured AlNiCoFeCrTi high-entropy coating performed by cold spray

Welding of High Entropy Alloys—A Review

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