Precipitation Hardenable High Entropy Alloy for Tooling Applications

MRS Advances ◽  
2019 ◽  
Vol 4 (25-26) ◽  
pp. 1427-1433
Author(s):  
O. Stryzhyboroda ◽  
U. Hecht ◽  
V. T. Witusiewicz ◽  
G. Laplanche ◽  
A. Asabre ◽  
...  
Keyword(s):  
Precipitation Hardening ◽  
High Entropy Alloy ◽  
Instrumented Indentation ◽  
Cast State ◽  
Alloy Development ◽  
High Entropy ◽  
Arc Melting ◽  
Thermodynamic Computations ◽  
Thermocalc Software ◽  
Cast Microstructure

ABSTRACTWe present a high entropy alloy (HEA) from the system Al-Co-Cr-Fe-Ni with small additions of W, Mo, Si and C which was designed to allow for precipitation hardening by annealing in the temperature range from 600 to 900 °C. The alloy development was supported by thermodynamic computations using ThermoCalc software and the specimens were produced by arc melting. The microstructure of one selected sample in as-cast and annealed conditions was analysed using SEM/EDS, SEM/EBSD and TEM. The as-cast microstructure consists of spinodally decomposed BCC dendrites enveloped by FCC+Cr23C6 eutectic. Upon annealing at 700 °C for 24 h nanoscale precipitates form within the spinodal BCC as well as from FCC. Precipitation is exquisitely uniform leading to an increase in microhardness from 415 HV0.5 in the as-cast state to 560 HV0.5 after annealing. We investigated coarsening of this microstructure using varying holding time for a constant temperature of 700 °C. The microstructure evolution during coarsening and the corresponding mechanical properties obtained from instrumented indentation experiments are presented in this work.

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.

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 Electrodeposition of high entropy alloy coating from water bath

2018 ◽  
Vol 62 (1) ◽  
pp. 1-5 ◽  
Author(s):  
J. Bárta ◽  
S. Ivanová ◽  
M. Pazderová
Keyword(s):  
Alloy Coating ◽  
Thin Layers ◽  
Water Bath ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Accelerated Corrosion ◽  
Metallic Substrates ◽  
High Entropy ◽  
Arc Melting ◽  
Accelerated Corrosion Tests

Abstract High entropy alloys (HEAs) have been in focus of scientist for past few years owing to their predicted scratch, corrosion and temperature resistance and also to interesting magnetic properties. They are usually prepared by arc melting of at least 5 pure elements. This article deals with electrodeposition of such five-element alloy from water bath, which have not been yet reported. The HEA coating consisting of Fe, Co, Ni, Mn and Mo or Zn was successfully electrodeposited on steel, copper and other metallic substrates. Substrates were polished and treated by sonication in acetone prior to electrodeposition. Obtained thin layers were documented by optical microscopy and SEM techniques. Their exact composition was determined by EDS and XRF analysis. Scratch and accelerated corrosion tests were performed to asses their resistance properties. Electrochemical properties were determined by measurements of polarization curves.

Aging temperature role on precipitation hardening in a non-equiatomic AlCoCrFeNiTi high-entropy alloy

2021 ◽  
pp. 1-10
Author(s):  
Vickey Nandal ◽  
K. Hariharan ◽  
R. Sarvesha ◽  
Sudhanshu S. Singh ◽  
E.-Wen Huang ◽  
...  
Keyword(s):  
Aging Temperature ◽  
Precipitation Hardening ◽  
High Entropy Alloy ◽  
High Entropy

Synthesis and Characterization of NiCoFeCrAl3 High Entropy Alloy Coating by Laser Cladding

2010 ◽  
Vol 97-101 ◽  
pp. 1408-1411 ◽  
Author(s):  
Hui Zhang ◽  
Yi Zhu He ◽  
Ye Pan ◽  
Yin Sheng He ◽  
Kee Sam Shin
Keyword(s):  
Laser Cladding ◽  
Alloy Coating ◽  
Synthesis And Characterization ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Arc Melting ◽  
Melting Technique

The NiCoFeCrAl3 high entropy alloy coating with a little addition of C, Si, Mn, Mo has been succesively synthesized by laser cladding. The results show that simple solution phases of ordered BCC and a small fraction of FCC are obtained with fine equaixed dendrites morphology. Because the fine grain strengthening obtained by rapid solidification and the additived small atomic elements like C, Si further increase the distortion of the solid solution lattice, The microhardness of the coating reached above 800 HV and is 50 % higher than previous study on the similar composition by arc melting technique.

Preparation of CoCrFeNiCuMnSix High Entropy Alloys and their Microstructure and Properties

2013 ◽  
Vol 750-752 ◽  
pp. 615-618 ◽  
Author(s):  
Li Sheng Zhang
Keyword(s):  
Phase Structure ◽  
Optical Microscope ◽  
Vacuum Arc ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Dendrite Morphology ◽  
High Entropy ◽  
Bcc Structure ◽  
Si Content ◽  
Cast Microstructure

According to the design concept of multi-element high-entropy alloys, seven kinds of elements (Cr, Mn, Fe, Co, Ni, Cu and Si) were selected in this work to design a series of CoCrFeNiCuMnSix high entropy alloys. Metal power was melted by vacuum arc furnace. Cast microstructure and phase structure of the high entropy alloy were Characterized by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD). And then, hardness, wear resistance and corrosion resistance were tested. Phase structure of cast microstructure, the morphology of the microstructure and mechanical properties of the CoCrFeNiCuMnSix high entropy alloys were researched systematic in the condition of different content Si. The results show that the crystal structure is simple BCC structure. With the increasing Si content, the alloy cast structure changes from dendrite morphology to cellular morphology. It was Si content that plays an important role in increasing significantly the hardness of the alloy. The hardness of the maximum value reaches to HV985.

Microstructure and Mechanical Properties of High-Entropy Alloys CoCrFeNiAl by Welding

2014 ◽  
Vol 936 ◽  
pp. 1635-1640 ◽  
Author(s):  
Lang Cui ◽  
Bing Ma ◽  
Sheng Qiang Feng ◽  
Xiu Ling Wang
Keyword(s):  
Mechanical Properties ◽  
Spot Welding ◽  
Dendritic Morphology ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Common Elements ◽  
High Entropy ◽  
Grain Sizes ◽  
Arc Melting ◽  
Microstructure And Mechanical Properties

Five common elements Co, Cr, Fe, Ni and Al were selected, and CoCrFeNiAl was prepared by arc-melting. The microstructure and mechanical properties after spot welding were studied. The results show that the cast microstructure of high entropy alloy CoCrFeNiAl is relatively uniform with a dendritic morphology. The heat is inversely proportional with the alloy grain sizes. The greater the heat is, the smaller the grain size is, which leads to the higher hardness and more uniform tissue. But there is a critical value of the heat(Hcrit) in spot welding. When Hactu(actual heat) exceeds Hcrit, it will adversely affect the performance, resulting in crack, splash and other defects.

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