Wear and Corrosion Behaviour of Supersaturated Surface Layers in the High-Entropy Alloy Systems CrMnFeCoNi and CrFeCoNi

The surface hardening of single-face-centred cubic (fcc)-phase CrMnFeCoNi and the manganese-free CrFeCoNi alloy was conducted using low-temperature nitrocarburisation. The microstructural investigations reveal the successful formation of a homogeneous diffusion layer with a thickness of approximately 16 µm. The interstitial solution of carbon and nitrogen causes an anisotropic lattice expansion. The increase in microhardness is in accordance to the graded concentration profile of the interstitial elements. Wear tests show a significantly enhanced resistance at different loads. The electrochemical tests reveal no deterioration in the corrosion resistance. The absence of precipitates is proven by microstructural investigations. The results prove the applicability of the concept of solution hardening by the formation of supersaturated solutions for the material group of high-entropy alloys. Hence, an increase of entropy with the consideration of lattice interstices provides new development approaches.

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Effect of Mn Addition on the Microstructures and Mechanical Properties of CoCrFeNiPd High Entropy Alloy

Entropy ◽

10.3390/e21030288 ◽

2019 ◽

Vol 21 (3) ◽

pp. 288

Author(s):

Yiming Tan ◽

Jinshan Li ◽

Jun Wang ◽

Hongchao Kou

Keyword(s):

Intermetallic Compound ◽

Interface Energy ◽

High Entropy Alloy ◽

Strengthening Effect ◽

Face Centered Cubic ◽

Liquid Interfaces ◽

High Entropy ◽

Single Face ◽

Face Centered ◽

Fcc Phase

CoCrFeNiPdMnx (x = 0, 0.2, 0.4, 0.6, 0.8) high entropy alloys (HEAs) were prepared and characterized. With an increase in Mn addition, the microstructures changed from dendrites (CoCrFeNiPd with a single face-centered-cubic (FCC) phase) to divorced eutectics (CoCrFeNiPdMn0.2 and CoCrFeNiPdMn0.4), to hypoeutectic microstructures (CoCrFeNiPdMn0.6), and finally to seaweed eutectic dendrites (CoCrFeNiPdMn0.8). The addition of Mn might change the interface energy anisotropy of both the FCC/liquid and MnPd-rich intermetallic compound/liquid interfaces, thus forming the seaweed eutectic dendrites. The hardness of the FCC phase was found to be highly related to the solute strengthening effect, the formation of nanotwins and the transition from CoCrFeNiPd-rich to CoCrFeNi-rich FCC phase. Hierarchical nanotwins were found in the MnPd-rich intermetallic compound and a decrease in either the spacing of primary twins or secondary twins led to an increase in hardness. The designing rules of EHEAs were discussed and the pseudo binary method was revised accordingly.

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Effect of the Annealing Treatment on the Microstructure, Microhardness and Corrosion Behaviour of Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.748.79 ◽

2013 ◽

Vol 748 ◽

pp. 79-85 ◽

Cited By ~ 2

Author(s):

L.C. Tsao ◽

C.S. Chen ◽

Kuo Huan Fan ◽

Yen Teng Huang

Keyword(s):

Corrosion Behaviour ◽

Dendritic Structure ◽

Annealing Treatment ◽

Age Hardening ◽

High Entropy Alloy ◽

Second Phase ◽

High Entropy Alloys ◽

High Entropy ◽

Fcc Phase ◽

Bcc Phase

In this study, an Al0.3CrFe1.5MnNi0.5high entropy alloy was synthesized by arc-melting in Ar. The as-cast alloy ingot was heat treated for 8 h at 650-750°C and then cooled in furnace to investigate the effects of age treatment on the microstructure, hardness and corrosion behaviour. The microstructure of as-cast sample has a typical rich-Cr BCC structure of dendrites, rich-Ni FCC interdendrite phases and a small fraction of cross-like rich-Ni FCC phase within the majority dendritic structure. During annealing treatment at 650°C, the cross-like FCC phase (β-FCC) gradually decreased, dendritic rich-Cr BCC phase transfers to Cr5Fe6Mn8phase, and the AlNi phase precipitated within the matrix dendrites. The interdendritic β1-FCC phases gradually decomposed and transfers to second-phase (β2FCC), and the AlNi precipitated phase coarsen during annealing at 750°C. In addition, Cr5Fe6Mn8phase gradually transfers to rich-Cr BCC phase during slow-cooling process. These precipitation phases in the grain matrix are the main age hardening mechanism. The potentiodynamic polarization of the Al0.3CrFe1.5MnNi0.5high entropy alloys, obtained in 3.5% NaCl solutions, clearly revealed that the corrosion resistance increases and the passive region decreases as annealing temperature increasing.

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Strengthening of a CoCrFeNiMn-Type High Entropy Alloy by Regular Arrays of Nanoprecipitates

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.772 ◽

2018 ◽

Vol 941 ◽

pp. 772-777 ◽

Cited By ~ 2

Author(s):

Nikita Stepanov ◽

Dmitry Shaysultanov ◽

Margarita Klimova ◽

Vladimir Sanin ◽

Sergey Zherebtsov

Keyword(s):

Cold Rolling ◽

Coarse Grained ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Single Face ◽

Cold Rolling And Annealing ◽

M23c6 Type ◽

Face Centered ◽

Fcc Phase

In this paper, we report microstructure and mechanical properties evolution of the CoCrFeNiMn-type high entropy alloy, containing small amounts of Al and C, during cold rolling and subsequent annealing at 700-1100°C. In the initial as-cast condition the alloy has coarse-grained single face-centered cubic (fcc) phase structure. Cold rolling and annealing substantially refine fcc grains; in addition M23C6 type carbides appear. After annealing at relatively low temperatures (≤900°C), these particles are arranged in characteristic arrays aligned with rolling directions. The specific microstructure of the thermomechanically processed alloy is suggested to be the reason of the balanced combination of tensile strength and ductility.

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High strength dual fcc phase CoCuFeMnNi high-entropy alloy wires with dislocation wall boundaries stabilized by phase boundaries

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141875 ◽

2021 ◽

pp. 141875

Author(s):

Sang Hun Shim ◽

Hesam Pouraliakbar ◽

Sun Ig Hong

Keyword(s):

High Strength ◽

High Entropy Alloy ◽

Phase Boundaries ◽

Dislocation Wall ◽

High Entropy ◽

Fcc Phase

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Phase Transition of As-Milled and Annealed CrCuFeMnNi High-Entropy Alloy Powder

NANO ◽

10.1142/s179329201850100x ◽

2018 ◽

Vol 13 (09) ◽

pp. 1850100 ◽

Cited By ~ 1

Author(s):

Rui-Feng Zhao ◽

Bo Ren ◽

Guo-Peng Zhang ◽

Zhong-Xia Liu ◽

Jian-Jian Zhang

Keyword(s):

Phase Transition ◽

Solution Structure ◽

Milling Time ◽

Structure Evolution ◽

High Entropy Alloy ◽

Chemical Homogeneity ◽

High Entropy ◽

Dynamic Phase Transition ◽

Fcc Phase ◽

Bcc Phase

The CrCuFeMnNi high entropy alloy (HEA) powder was synthesized by mechanical alloying. The effects of milling time and subsequent annealing on the structure evolution, thermostability and magnetic property were investigated. After 50[Formula: see text]h of milling, the CrCuFeMnNi HEA powder consisted of a major FCC phase and a small amount of BCC phase. The crystallite size and strain lattice of 50[Formula: see text]h-ball-milled CrCuFeMnNi HEA powder were 12[Formula: see text]nm and 1.02%, respectively. The powder exhibited refined morphology and excellent chemical homogeneity. The supersaturated solid solution structure of the as-milled HEA powder transformed into FCC1, FCC2, a small amount of BCC and [Formula: see text] phase in annealed state. Most of the BCC phase decomposed into FCC (mainly FCC2 phase) and [Formula: see text] phases, and the dynamic phase transition was almost in equilibrium at 900[Formula: see text]C. The saturated magnetization and coercivity force of the 50[Formula: see text]h-ball-milled CrCuFeMnNi HEA powder were respectively 16.1[Formula: see text]emu/g and 56.2[Formula: see text]Oe.

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