scholarly journals Bimodal Microstructure Design of CrMnFeCoNi High-Entropy Alloy Using Powder Metallurgy

2021 ◽  
Vol 70 (8) ◽  
pp. 648-655
Author(s):  
Keisuke FUJITA ◽  
Hiroshi FUJIWARA ◽  
Shoichi KIKUCHI
Keyword(s):  
Powder Metallurgy ◽  
High Entropy Alloy ◽  
Bimodal Microstructure ◽  
Microstructure Design ◽  
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%.

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.

Compression stress strengthening modelling of a ultrafine-grained equiatomic SPS CoCrFeNiNb high-entropy alloy

2020 ◽  
pp. 095440622094324
Author(s):  
Marcello Cabibbo ◽  
Filip Průša ◽  
Alexandra Šenková ◽  
Andrea Školáková ◽  
Vojtěch Kučera ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Mechanical Alloying ◽  
Oxide Phase ◽  
High Entropy Alloy ◽  
Induction Melting ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Spark Plasma

High-entropy alloys are known to show exceptionally high mechanical properties, both compression and tensile strength, and unique physical properties, such as their phase stability. These quite unusual properties are primarily due to the microstructure generated by mechanical alloying processes, such as conventional induction arc melting, powder metallurgy, or mechanical alloying. In the present study, an equiatomic CoCrFeNiNb high-entropy alloy was prepared by a sequence of conventional induction melting, powder metallurgy, and compaction via spark plasma sintering. The high-entropy alloys showed uniform sub-micrometer grain microstructure consisted by a mixture of an fcc solid solution strengthened by a hcp Laves phase and a third intergranular oxide phase. The as-cast high-entropy alloys showed an ultimate compression strength (UCS) of ∼1400 MPa, which after sintering and compaction at 1273 K increased up to ∼2400 MPa. Extensive transmission electron microscopy quantitative analyses were carried out to model the UCS. A quite good agreement between the microstructure-strengthening model and the experimental UCS was found.

scholarly journals Powder metallurgy of Al0.1CoCrFeNi high-entropy alloy

2020 ◽  
Vol 35 (21) ◽  
pp. 2835-2847
Author(s):  
Rathinavelu Sokkalingam ◽  
Marek Tarraste ◽  
Kumar Babu Surreddi ◽  
Valdek Mikli ◽  
Veerappan Muthupandi ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
High Entropy Alloy ◽  
High Entropy

Abstract

scholarly journals Atom probe tomography study of an Fe25Ni25Co25Ti15Al10 high-entropy alloy fabricated by powder metallurgy

2019 ◽  
Vol 179 ◽  
pp. 372-382
Author(s):  
Zhiqiang Fu ◽  
Andrew Hoffman ◽  
Benjamin E. MacDonald ◽  
Zhenfei Jiang ◽  
Weiping Chen ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
High Entropy Alloy ◽  
High Entropy

scholarly journals Microstructure and Mechanical Property Evolution during Annealing of a Cold-Rolled Metastable Powder Metallurgy High Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (9) ◽  
pp. 833 ◽  
Author(s):  
Li ◽  
Qiu ◽  
Guo ◽  
Liu ◽  
Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Tensile Strength ◽  
Powder Metallurgy ◽  
Cold Deformation ◽  
Precipitation Strengthening ◽  
High Entropy Alloy ◽  
Σ Phase ◽  
High Entropy ◽  
Fine Grain

Precipitation strengthening is an effective approach to strengthen high-entropy alloys (HEAs) with a simple face-center-cubic (FCC) structure. In this work, CoCrFeNiMo0.2 HEAs were prepared by powder metallurgy, followed by cool rolling and subsequent heat-treatment at different temperatures. The effects of cold working and annealing on microstructure and mechanical properties have been investigated. Results show the fine and dispersed (Cr, Mo)-rich σ phase with a topologically close-packed structure precipitated in the FCC matrix after the prior cold deformation process, which enhanced the mechanical property of the CoCrFeNiMo0.2 alloy. The HEA annealed at 600 °C for 48 h had a tensile strength of 1.9 GPa but an elongation which decreased to 8%. The HEA annealed at 800 °C for 12 h exhibited a tensile strength of 1.2 GPa and an elongation of 31%. These outstanding mechanical properties can be attributed to precipitation strengthening and fine-grain strengthening.

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