scholarly journals Synthesis of Spherical V-Nb-Mo-Ta-W High-Entropy Alloy Powder Using Hydrogen Embrittlement and Spheroidization by Thermal Plasma

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1296 ◽  
Author(s):  
Won-Hyuk Lee ◽  
Ki Beom Park ◽  
Kyung-Woo Yi ◽  
Sung Yong Lee ◽  
Kwangsuk Park ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Thermal Plasma ◽  
Fine Powder ◽  
Hydrogen Atmosphere ◽  
Vacuum Arc ◽  
Cubic Phase ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Inductively Coupled ◽  
Arc Melting

V-Nb-Mo-Ta-W high-entropy alloy (HEA), one of the refractory HEAs, is considered as a next-generation structural material for ultra-high temperature uses. Refractory HEAs have low castability and machinability due to their high melting temperature and low thermal conductivity. Thus, powder metallurgy becomes a promising method for fabricating components with refractory HEAs. Therefore, in this study, we fabricated spherical V-Nb-Mo-Ta-W HEA powder using hydrogen embrittlement and spheroidization by thermal plasma. The HEA ingot was prepared by vacuum arc melting and revealed to have a single body-centered cubic phase. Hydrogen embrittlement which could be achieved by annealing in a hydrogen atmosphere was introduced to get the ingot pulverized easily to a fine powder having an angular shape. Then, the powder was annealed in a vacuum atmosphere to eliminate the hydrogen from the hydrogenated HEA, resulting in a decrease in the hydrogen concentration from 0.1033 wt% to 0.0003 wt%. The angular shape of the HEA powder was turned into a spherical one by inductively-coupled thermal plasma, allowing to fabricate spherical V-Nb-Mo-Ta-W HEA powder with a d50 value of 28.0 μm.

scholarly journals Microstructure and Mechanical Properties of Co-Cr-Mo-Si-Y-Zr High Entropy Alloy

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1456
Author(s):  
Karsten Glowka ◽  
Maciej Zubko ◽  
Paweł Świec ◽  
Krystian Prusik ◽  
Robert Albrecht ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Microstructure Analysis ◽  
Vacuum Arc ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Transmission Electron ◽  
Multi Phase ◽  
Principal Elements

Presented work was focused on obtaining new, up to our knowledge, non-described previously in the literature high entropy Co15Cr15Mo25Si15Y15Zr15 alloy to fill in the knowledge gap about the six-elemental alloys located in the adjacent to the center of phase diagrams. Material was obtained using vacuum arc melting. Phase analysis revealed the presence of a multi-phase structure. Scanning electron microscopy microstructure analysis revealed the existence of three different phases with partially dendritic structures. Chemical analysis showed that all phases consist of all six principal elements—however, with different proportions. Transmission electron microscopy microstructure analysis confirmed the presence of amorphous and nanocrystalline areas, as well as their mixture. For the studied alloy, any phase transformation and solid-state crystallization were not revealed in the temperature range from room temperature up to 1350 °C. Nanoindentation measurements revealed high nanohardness (13(2) GPa and 18(1) GPa for dendritic and interdendritic regions, respectively) and relatively low Young’s modulus (185(23) GPa and 194(9) GPa for dendritic and interdendritic regions, respectively) of the observed phases.

scholarly journals Preparation of Spherical Mo5Si3 Powder by Inductively Coupled Thermal Plasma Treatment

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 604
Author(s):  
Jang-Won Kang ◽  
Jong Park ◽  
Byung Choe ◽  
Seong Lee ◽  
Jung Park ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Thermal Plasma ◽  
Liquid Mixture ◽  
Spherical Shape ◽  
Vacuum Arc ◽  
Plasma Power ◽  
Inductively Coupled ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Inductively Coupled Thermal Plasma

A method was developed to fabricate spherical Mo5Si3 powder by milling and spheroidizing using inductively coupled thermal plasma. A Mo5Si3 alloy ingot was fabricated by vacuum arc melting, after which it was easily pulverized into powder by milling due to its brittle nature. The milled powders had an irregular shape, but after being spheroidized by the thermal plasma treatment, they had a spherical shape. Sphericity was increased with increasing plasma power. After plasma treatment, the percentage of the Mo3Si phase had increased due to Si evaporation. The possibility of Si evaporation was thermodynamically analyzed based on the vapor pressure of Mo and Si in the Mo5Si3 liquid mixture. By this process, spherical Mo silicide powders with high purity could be fabricated successfully.

Preparation of spherical WTaMoNbV refractory high entropy alloy powder by inductively-coupled thermal plasma

2019 ◽  
Vol 255 ◽  
pp. 126513 ◽  
Author(s):  
Jong-Min Park ◽  
Jang-Won Kang ◽  
Won-Hyuk Lee ◽  
Sung Yong Lee ◽  
Seok-Hong Min ◽  
...  
Keyword(s):  
Thermal Plasma ◽  
Alloy Powder ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Inductively Coupled ◽  
Inductively Coupled Thermal Plasma

scholarly journals MICROSTRUCTURE AND MECHANICAL PROPERTIES OF REFRACTORY HIGH-ENTROPY ALLOY HfMoNbTiCr

2021 ◽  
Vol 55 (2) ◽  
pp. 305-310
Author(s):  
Jiaojiao Yi ◽  
Lu Wang ◽  
Mingqin Xu ◽  
Lin Yang
Keyword(s):  
Cast Alloy ◽  
Vital Role ◽  
Stress Fields ◽  
Vacuum Arc ◽  
High Entropy Alloy ◽  
Laves Phases ◽  
High Entropy ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Bcc Phase

A new refractory alloy, HfMoNbTiCr, was obtained by replacing Zr with Cr or Mo in the HfMoNbTiZr or HfNbTiCrZr alloys using vacuum arc melting. The phase components, microstructures and compressive properties of the alloy in the as-cast and annealed states were investigated. The results showed that the phase components changed from a single BCC phase in HfMoNbTiZr and BCC+Laves phases in HfNbTiCrZr to multiple phases – primarily two BCC phases and two cubic Laves phases – in HfMoNbTiCr. Notably, the yield and ultimate compressive strength of the as-cast alloy significantly increased from 1719 and 1803 MPa to 1851 and 2489 MPa, without a decrease in the ductility. The stress fields induced by Mo and the Cr-containing Laves phases were responsible for the enhanced strength, while the stiff network-like framework composed of intrinsically-strong Cr-containing Laves phases may have played a vital role in retaining the ductility.

Microstructure and Mechanical Properties of VTaTiMoAlx Refractory High Entropy Alloys

2017 ◽  
Vol 898 ◽  
pp. 638-642 ◽  
Author(s):  
Dong Xu Qiao ◽  
Hui Jiang ◽  
Xiao Xue Chang ◽  
Yi Ping Lu ◽  
Ting Ju Li
Keyword(s):  
Mechanical Properties ◽  
Vacuum Arc ◽  
High Entropy Alloys ◽  
X Ray Diffraction ◽  
Dendrite Structure ◽  
X Ray ◽  
High Entropy ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Microstructure And Mechanical Properties

A series of refractory high-entropy alloys VTaTiMoAlx with x=0,0.2,0.6,1.0 were designed and produced by vacuum arc melting. The effect of added Al elements on the microstructure and mechanical properties of refractory high-entropy alloys were investigated. The X-ray diffraction results showed that all the high-entropy alloys consist of simple BCC solid solution. SEM indicated that the microstructure of VTaTiMoAlx changes from equiaxial dendritic-like structure to typical dendrite structure with the addition of Al element. The composition of different regions in the alloys are obtained by energy dispersive spectroscopy and shows that Ta, Mo elements are enriched in the dendrite areas, and Al, Ti, V are enriched in inter-dendrite areas. The yield strength and compress strain reach maximum (σ0.2=1221MPa, ε=9.91%) at x=0, and decrease with the addition of Al element at room temperature. Vickers hardness of the alloys improves as the Al addition.

scholarly journals Hydrogen embrittlement of additively manufactured AlCoCrFeNi2.1 eutectic high-entropy alloy

2022 ◽  
Vol 195 ◽  
pp. 110007
Author(s):  
Di Wan ◽  
Shuai Guan ◽  
Dong Wang ◽  
Xu Lu ◽  
Jun Ma
Keyword(s):  
Hydrogen Embrittlement ◽  
High Entropy Alloy ◽  
High Entropy

scholarly journals Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1324 ◽  
Author(s):  
Jaroslav Málek ◽  
Jiří Zýka ◽  
František Lukáč ◽  
Jakub Čížek ◽  
Lenka Kunčická ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Dendritic Structure ◽  
Cold Isostatic Pressing ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Arc Melting ◽  
Powder Metallurgy Process ◽  
Heat Treated ◽  
Near Net Shape ◽  
Metallurgy Process

High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.

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