scholarly journals Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Q. Hu ◽  
S. Guo ◽  
J.M. Wang ◽  
Y.H. Yan ◽  
S.S. Chen ◽  
...  
Keyword(s):  
Crystalline Structure ◽  
Parametric Study ◽  
Atomic Radius ◽  
Alloying Elements ◽  
High Entropy Alloys ◽  
High Entropy

scholarly journals Effect of Copper Addition on the AlCoCrFeNi High Entropy Alloys Properties via the Electroless Plating and Powder Metallurgy Technique

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 540
Author(s):  
Mohamed Ali Hassan ◽  
Hossam M. Yehia ◽  
Ahmed S. A. Mohamed ◽  
Ahmed Essa El-Nikhaily ◽  
Omayma A. Elkady
Keyword(s):  
Compressive Strength ◽  
Powder Metallurgy ◽  
Atomic Radius ◽  
The Other ◽  
High Entropy Alloy ◽  
Coating Process ◽  
High Entropy Alloys ◽  
Powder Metallurgy Technique ◽  
Copper Metal ◽  
High Entropy

To improve the AlCoCrFeNi high entropy alloys’ (HEAs’) toughness, it was coated with different amounts of Cu then fabricated by the powder metallurgy technique. Mechanical alloying of equiatomic AlCoCrFeNi HEAs for 25 h preceded the coating process. The established powder samples were sintered at different temperatures in a vacuum furnace. The HEAs samples sintered at 950˚C exhibit the highest relative density. The AlCoCrFeNi HEAs model sample was not successfully produced by the applied method due to the low melting point of aluminum. The Al element’s problem disappeared due to encapsulating it with a copper layer during the coating process. Because the atomic radius of the copper metal (0.1278 nm) is less than the atomic radius of the aluminum metal (0.1431 nm) and nearly equal to the rest of the other elements (Co, Cr, Fe, and Ni), the crystal size powder and fabricated samples decreased by increasing the content of the Cu wt%. On the other hand, the lattice strain increased. The microstructure revealed that the complete diffusion between the different elements to form high entropy alloy material was not achieved. A dramatic decrease in the produced samples’ hardness was observed where it decreased from 403 HV at 5 wt% Cu to 191 HV at 20 wt% Cu. On the contrary, the compressive strength increased from 400.034 MPa at 5 wt% Cu to 599.527 MPa at 15 wt% Cu with a 49.86% increment. This increment in the compressive strength may be due to precipitating the copper metal on the particles’ surface in the nano-size, reducing the dislocations’ motion, increasing the stiffness of produced materials. The formability and toughness of the fabricated materials improved by increasing the copper’s content. The thermal expansion has increased gradually by increasing the Cu wt%.

Solid State Manufacture of High Entropy Alloys-Preliminary Studies

MRS Advances ◽  
2017 ◽  
Vol 2 (26) ◽  
pp. 1375-1380 ◽  
Author(s):  
M B D Ellis ◽  
G R Doughty
Keyword(s):  
Solid State ◽  
High Performance ◽  
Alloying Elements ◽  
Liquid Density ◽  
High Entropy Alloys ◽  
Next Generation ◽  
Molten Salt Electrolysis ◽  
High Entropy ◽  
State Diffusion ◽  
Environmentally Friendly Process

AbstractFor the past ten years Metalysis have produced tantalum, titanium and titanium alloy powders for high performance applications using their solid state salt electrolysis process. This low energy and environmentally friendly process is now being used to manufacture the next generation of High Entropy Alloys (HEAs).In most cases the manufacture of HEAs involves high temperatures which put all of the alloying elements into the liquid phase. This can lead to numerous problems and restrict the number of HEAs which can be made, particularly the alloys where one needs to combine low melting point elements with refractory elements and also where there are significant liquid density differences between the constituents causing melt segregation.The aim is to present the preliminary work carried out by Metalysis and to show how the solid state diffusion process based on molten salt electrolysis lends itself to the industrial scale manufacture of the next generation of HEAs. This study will focus on the HEAs whose constituent alloying elements have large differences in both their melting points and liquid densities, for example, chromium, niobium, tantalum, titanium and aluminum.

Microstructure of Rapidly Solidified Melt-Spun Ribbon in AlCoCrFeNi2.1 Eutectic High-Entropy Alloys

2016 ◽  
Vol 879 ◽  
pp. 1350-1354 ◽  
Author(s):  
Takeshi Nagase ◽  
Mamoru Takemura ◽  
Mitsuaki Matsumuro
Keyword(s):  
Grain Boundary ◽  
Rapid Solidification ◽  
Crystalline Structure ◽  
Xrd Analysis ◽  
Solidification Structure ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Melt Spun ◽  
Melt Spun Ribbons ◽  
Rapidly Solidified

The microstructure of rapidly solidified melt-spun ribbon in AlCoCrFeNi2.1 eutectic high entropy alloys (EHEAs) was investigated for clarifying the effect of rapid solidification on the constituent phases and microstructure of specimens formed through solidification. XRD analysis indicates that the melt-spun ribbons were composed of a mixture of fcc and bcc phases. The rapidly solidified melt-spun ribbon shows a fine poly-crystalline structure with fcc matrix phase and crystalline precipitates in the grain boundary, indicating that the solidification structure in the melt-spun ribbon was significantly different from that obtained by conventional casting processes.

scholarly journals Strengthening Mechanisms in CoCrFeNiX0.4 (Al, Nb, Ta) High Entropy Alloys Fabricated by Powder Plasma Arc Additive Manufacturing

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 721
Author(s):  
Yupeng Zhang ◽  
Qingkai Shen ◽  
Xizhang Chen ◽  
Subramanian Jayalakshmi ◽  
Ramachandra Arvind Singh ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Atomic Radius ◽  
Eutectic Structure ◽  
Precipitation Strengthening ◽  
High Entropy Alloys ◽  
Plasma Arc ◽  
High Entropy ◽  
Solid Solution Strengthening ◽  
Solution Strengthening

In high entropy alloys (HEAs), the addition of large-size atoms results in lattice distortion and further leads to solid solution strengthening or precipitation strengthening. However, the relationship between atomic radius, solid solution strengthening and precipitation strengthening has not been discerned yet. In this work, CoCrFeNiX0.4 (X = Al, Nb, Ta, with an equi-atomic radius) HEAs were prepared by powder plasma arc additive manufacturing (PPA-AM) and evaluated for their mechanical properties. Compression and nano-indentation hardness tests showed that the HEA with Ta showed the best properties. The influence of atomic radius and solid solubility on solid solution strengthening was investigated and the main strengthening mechanism that determines the mechanical properties of the developed HEAs was analyzed. The results showed that (i) the CoCrFeNiAl0.4 alloy did not show any solid solution strengthening effect and that a clear relation between solid solution strengthening and atomic size was not observed; (ii) in both CoCrFeNiTa0.4 and CoCrFeNiNb0.4 HEAs, precipitation strengthening and grain boundary strengthening effects are observed, wherein the difference in mechanical properties between both the alloys can be mainly attributed to the formation of fine eutectic structure in CoCrFeNiTa0.4; and (iii) from the microstructural analyses, it was identified that, in the CoCrFeNiTa0.4 HEA, the location containing a fine eutectic structure is accompanied by the formation of low-angle grain boundaries (LAGBs), which is also the region where deformed grains gather, giving rise to improved mechanical strengthening.

Replacement of Ta with equi-atomic radius Nb atoms in CoCrFeNiTa high entropy alloys: Effect on microstructure and mechanical properties

2021 ◽  
Vol 297 ◽  
pp. 129966
Author(s):  
Yupeng Zhang ◽  
Xizhang Chen ◽  
S. Jayalakshmi ◽  
R. Arvind Singh ◽  
Sergey Konovalov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Atomic Radius ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Microstructure And Mechanical Properties

Influence of alloying elements on mechanical and electronic properties of NbMoTaWX (X = Cr, Zr, V, Hf and Re) refractory high entropy alloys

2020 ◽  
Vol 126 ◽  
pp. 106928
Author(s):  
Yonggang Tong ◽  
Linhui Bai ◽  
Xiubing Liang ◽  
Yongxiong Chen ◽  
Zhibing Zhang ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Alloying Elements ◽  
High Entropy Alloys ◽  
High Entropy
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