scholarly journals Structure of AlCoCrFeNi high-entropy alloy after uniaxial compression and heat treatment

2021 ◽  
Vol 64 (10) ◽  
pp. 736-746
Author(s):  
I. V. Ivanov ◽  
K. I. Emurlaev ◽  
A. A. Ruktuev ◽  
A. G. Tyurin ◽  
I. A. Bataev
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Uniaxial Compression ◽  
Thermal Studies ◽  
Cold Deformation ◽  
Dendritic Structure ◽  
High Entropy Alloy ◽  
Relaxation Processes ◽  
High Temperature Annealing ◽  
High Entropy

In this study, we discuss the structure and properties of high-entropy AlCoCrFeNi alloy after casting, cold deformation, and heat treatment. Ingots of the investigated alloys were obtained by arc melting method in argon atmosphere. In order to ensure a homogeneous chemical composition, ingots were remelted several times. Cylindrical samples of 5 mm in diameter and 8 mm in height were cut from ingots by electrospark method for mechanical tests. Subsequently, samples were subjected to uniaxial compression by 5, 11, and 23 %. During the tests, compression curves were recorded, and limit of proportionality of the analyzed alloys was calculated. High-temperature annealing and thermal studies were performed using thermogravimetric analyzer. Thermal studies were carried out in a cyclic mode (3 cycles, including heating up to 1200 °C at a rate of 20 °C/min and cooling at a rate of 20 °C/min). High-temperature annealing was carried out at a temperature of 1200 °C for 5 hours. Such annealing of cast alloys promotes material homogenization and eliminates dendritic structure. The alloy presents limited plasticity. Grain boundaries are effective barriers preventing crack propagation. The studies indicate that plastic deformation has a significant effect on development of relaxation processes during subsequent heat treatment. An increase in strain during the compression leads to a higher rate of healing processes of defects in crystal structure.

scholarly journals Influence of heat-treatment on microstructure and hardness of Al0.5Cr0.5Ni0.5TiZr1.5Nb1.5 high entropy alloy

2019 ◽  
Vol 1 (1) ◽  
pp. 25-26
Keyword(s):  
Heat Treatment ◽  
Treatment Process ◽  
Chemical Elements ◽  
Dendritic Structure ◽  
Argon Atmosphere ◽  
Emission Spectrometry ◽  
High Entropy Alloy ◽  
Induction Melting ◽  
Heat Treatment Process ◽  
High Entropy

High entropy alloys (HEA) are a new class of multicomponent alloys that contain 5 to 13 elements in equimolar or near equimolar ration. These types of alloys can develop superior properties like: high temperature stability, high hardness, high corrosion resistance etc. Depending on the composition and the synthesis technique, HEA properties can vary and permanently change in particular conditions. High entropy alloy was synthetized by induction melting in argon atmosphere from high purity metal chunks. During the melting process temperature of 1900°C was reached. The melt was cast in a copper mould in argon atmosphere and slowly cooled. Resulted ingot was cleaned and analysed by Inductively coupled plasma - optical emission spectrometry (ICP-OES) and Scanning Electron Microscopy (SEM). A piece of the HEA ingot was prepared for heat treatment process. Heat treatment of HEA in argon atmosphere at 900° C for 10 hours reveals a growth of the dendritic structure and a closing up of the inter-dendritic zones. The hardness of the alloy is increasing from the heat-treatment process due to formation of hard bcc structures. SEM study highlighted the sample morphology and the differences appeared due to the modification of the structure by heat treatment, under controlled conditions. Also, by the Energy Dispersive X-Ray Spectroscopy (EDS) technique, the component chemical elements of the obtained phases were observed.

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

Coatings ◽  
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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