Effect of heat treatment on the microstructure and hardness of Al0.3CoCrFeNi high entropy alloy

Abstract In this study, the cold-rolled Al0.3CoCrFeNi high entropy alloys were heat treated at 900°C for 30min and 1050°C for 20min, respectively, to investigate the effect of heat treatment on the microstructure of the alloy. The results showed that grain refinement occurred in the 900°C/30min annealed sample, while remarkable equiaxial grains and twins appeared in the 1050°C/20min annealed sample. The hardness of samples showed a decrease trend following: as-rolled sample, 900°C/30min annealed sample, and 1050°C/20min annealed sample, which can be attributed to the dislocation elimination caused by recovery and recrystallization.

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Microstructural Characterization of AlCrTiV – Si High Entropy Alloy for advanced applications

MATEC Web of Conferences ◽

10.1051/matecconf/202134902003 ◽

2021 ◽

Vol 349 ◽

pp. 02003

Author(s):

Ioannis Daskalopoulos ◽

Spyridon Chaskis ◽

Marianthi Bouzouni ◽

Pavlos Stavroulakis ◽

Russell Goodall ◽

...

Keyword(s):

Heat Treatment ◽

Microstructural Characterization ◽

High Entropy Alloy ◽

Strength Increase ◽

Worst Case ◽

High Entropy ◽

Heat Treated ◽

The Matrix ◽

Advanced Applications

This work deals with the microstructural characterization of two equiatomic high-entropy, low-density alloys (HEA), the AlCrTiV and AlCrTiV-Si7.2. These alloys can serve as potential candidates for advanced applications where high strength and enhanced ductility is demanded. For ensuring high ductility the alloys must contain as minimum as possible hard precipitates. As the strength increase is based on both solid solution and precipitation hardening, the laboratory made alloys were investigated in as-cast and heat-treated conditions. For the heat treatment a high soaking temperature of 1200°C for 8 hours was selected to ensure microstructure homogenization. Micrographic observations of the AlCrTiV and AlCrTiV-Si7.2 samples in the as-cast condition indicated the presence of a dendritic microstructure. Furthermore, chemical micro-analysis showed segregation in the matrix in both samples. This is a critical result as this segregation will lead to heavy precipitation at interdendritic regions, it may sensitize these regions and in the worst-case scenario may cause cleavage fracture in the micro scale, which can trigger brittle fracture during cooling even without the application of deformation. However, the selected heat treatment eliminated the segregation phenomena forcing the alloying elements to be uniformly distributed in the matrix. At the center of the heat-treated AlCrTiV-Si7.2 sample the fragmentation and spheroidization of the intermetallic phase Ti5Si3 was observed. For the same sample, at the mold-sample’s interface, the particles Ti5Si3 were shown to dissolve and form aggregates. Both alloys exhibited high hardness values with small differences between the as-cast and heat-treated conditions, which indicates that the AlCrTiV–Si7.2 high entropy alloy presents high yield strength and may operate at high temperatures without deterioration of the mechanical properties nor unexpected failure.

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Effect of Heat Treatment on the Microstructure, Phase Distribution, and Mechanical Properties of AlCoCuFeMnNi High Entropy Alloy

Advances in Materials Science and Engineering ◽

10.1155/2017/1950196 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 2

Author(s):

Gulhan Cakmak

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Yield Strength ◽

Phase Distribution ◽

Cast Alloy ◽

Lattice Parameters ◽

High Entropy Alloy ◽

Second Phase ◽

High Entropy ◽

Heat Treated

The present paper reports the synthesis of AlCoCuFeMnNi high entropy alloy (HEA) with arc melting process. The as-cast alloy was heat treated at 900°C for 8 hours to investigate the effect of heat treatment on the structure and properties. Microstructural and mechanical properties of the alloy were analyzed together with the detailed phase analysis of the samples. The initially as-cast sample was composed of two separate phases with BCC and FCC structures having lattice parameters of 2.901 Å and 3.651 Å, respectively. The heat-treated alloy displays microsized rod-shaped precipitates both in the matrix and within the second phase. Rietveld refinement has shown that the structure was having three phases with lattice parameters of 2.901 Å (BCC), 3.605 Å (FCC1), and 3.667 Å (FCC2). The resulting phases and distribution of phases were also confirmed with the TEM methods. The alloys were characterized mechanically with the compression and hardness tests. The yield strength, compressive strength, and Vickers hardness of the as-cast alloy are 1317 ± 34 MPa, 1833 ± 45 MPa, and 448 ± 25 Hv, respectively. Heat treatment decreases the hardness values to 419 ± 26 Hv. The maximum compressive stress of the alloy increased to 2123 + 41 MPa while yield strength decreased to 1095 ± 45 with the treatment.

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Effect of Heat Treatment on the Phase Composition, Microstructure and Mechanical Properties of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 High-Entropy Alloys

Metals ◽

10.3390/met8110974 ◽

2018 ◽

Vol 8 (11) ◽

pp. 974 ◽

Cited By ~ 1

Author(s):

Lijia Chen ◽

Kirsten Bobzin ◽

Zheng Zhou ◽

Lidong Zhao ◽

Mehmet Öte ◽

...

Keyword(s):

Mechanical Properties ◽

Phase Transition ◽

Heat Treatment ◽

Phase Composition ◽

Elevated Temperatures ◽

Intermetallic Phase ◽

Phase Changes ◽

High Entropy Alloys ◽

High Entropy ◽

Heat Treated

High-entropy alloys exhibit some interesting mechanical properties including an excellent resistance against softening at elevated temperatures. This gives high-entropy alloys (HEAs) great potential as new structural materials for high-temperature applications. In a previous study of the authors, oxidation behavior of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys at T = 800 °C, 900 °C and 1000 °C was investigated. Si-alloying was found to increase the oxidation resistance by promoting the formation of a continuous Al2O3 layer, avoiding the formation of AlN at T = 800 °C. Obvious phase changes were identified in the surface areas of both alloys after the oxidation experiments. However, the effects of heat treatment and Si-alloying on the phase transition in the bulk were not investigated yet. In this study, Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys were heat-treated at T = 800 °C and T = 1000 °C to investigate the effect of heat treatment on microstructure, phase composition and mechanical properties of both alloys. The results show that alloying Al0.6CrFeCoNi with Si caused a phase transition from dual phases consisting of BCC and FCC to a single BCC phase in an as-cast condition. Furthermore, increased hardness for as-cast and heat-treated samples compared with the Al0.6CrFeCoNi alloy was observed. In addition, the heat treatment facilitated the phase transition and the precipitation of the intermetallic phase, which resulted in the change of the mechanical properties of the alloys.

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An as-cast high-entropy alloy with remarkable mechanical properties strengthened by nanometer precipitates

Nanoscale ◽

10.1039/c9nr08338c ◽

2020 ◽

Vol 12 (6) ◽

pp. 3965-3976 ◽

Cited By ~ 9

Author(s):

Gang Qin ◽

Ruirun Chen ◽

Peter K. Liaw ◽

Yanfei Gao ◽

Liang Wang ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

High Strength ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

High Entropy ◽

Good Ductility ◽

Treatment Processes

High-entropy alloys (HEAs) with good ductility and high strength are usually prepared by a combination of forging and heat-treatment processes.

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The Effects of Annealing at Different Temperatures on Microstructure and Mechanical Properties of Cold-Rolled Al0.3CoCrFeNi High-Entropy Alloy

Metals ◽

10.3390/met11060940 ◽

2021 ◽

Vol 11 (6) ◽

pp. 940

Author(s):

Zichao Zhu ◽

Tongtong Yang ◽

Ruolan Shi ◽

Xuantong Quan ◽

Jinlong Zhang ◽

...

Keyword(s):

Mechanical Properties ◽

Cold Rolling ◽

Annealing Temperature ◽

Crystal Defects ◽

High Entropy Alloy ◽

Rolled Sample ◽

High Entropy ◽

Cold Rolling And Annealing ◽

Cold Rolled ◽

Strength And Toughness

In this work, cold-rolling was utilized to induce a high density of crystal defects in Al0.3CoCrFeNi high-entropy alloys. The effects of annealing temperature on static recrystallization, precipitation behavior and mechanical properties were investigated. With increasing annealing temperature from 590 °C to 800 °C, the area fraction of recrystallized region increases from 26.9% to 93.9%. Cold-rolling deformation largely promotes the precipitation of B2 phases during annealing, and the characteristics of the precipitates are linked to recrystallization level. The coarse and equiaxed B2 phases exist in the recrystallized region and the fine and elongated B2 phases occupy the non-recrystallized region. Combined use of cold-rolling and annealing can remarkably enhance the strength and toughness. A partially recrystallized microstructure in a cold-rolled sample annealed at 700 °C exhibits a better combination of strength and toughness than a fully recrystallized microstructure in a cold-rolled sample annealed at 800 °C. Finally, related mechanisms are discussed.

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

Crystals ◽

10.3390/cryst11050540 ◽

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%.

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A review on phase prediction in high entropy alloys

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211008935 ◽

2021 ◽

pp. 095440622110089

Author(s):

Vinay Kumar Soni ◽

S Sanyal ◽

K Raja Rao ◽

Sudip K Sinha

Keyword(s):

Solid Solution ◽

Phase Formation ◽

Single Phase ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Modeling Tools ◽

High Entropy ◽

Recent Developments ◽

Phase Prediction ◽

The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

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Influence of V and Heat Treatment on Characteristics of WMoNbTaV Refractory High-Entropy Alloy Coatings by Mechanical Alloying

Coatings ◽

10.3390/coatings11030265 ◽

2021 ◽

Vol 11 (3) ◽

pp. 265

Author(s):

Chun-Liang Chen ◽

Sutrisna

Keyword(s):

Heat Treatment ◽

Mechanical Alloying ◽

Annealing Treatment ◽

High Energy ◽

304 Stainless Steel ◽

Homogeneous Distribution ◽

High Entropy Alloy ◽

Solid Solution Phase ◽

High Entropy ◽

Steel Substrates

Refractory high-entropy alloy (RHEA) is one of the most promising materials for use in high-temperature structural materials. In this study, the WMoNbTaV coatings on 304 stainless steel substrates has been prepared by mechanical alloying (MA). Effects of V addition and subsequent heat treatment on properties of the WMoNbTaV coatings were investigated. The results show that the RHEA coatings with nanocrystalline body-centered cubic (BCC) solid-solution phase were generated by the mechanical alloying process. The presence of the V element promotes a uniform microstructure and homogeneous distribution of composition in the RHEA coatings due to improving alloying efficiency, resulting in an increase of hardness. After the annealing treatment of the RHEA coatings, microstructure homogeneity was further enhanced; however, the high affinity of Ta for oxygen causes the formation of Ta-rich oxides. Annealing also removes strain hardening generated by high-energy ball milling and thus decreases the hardness of the RHEA coating and alters microstructure evolution and mechanical properties.

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