China 
Africa 
Explore chapters and articles related to this topic
High Entropy Alloys
Published in T.S. Srivatsan, Manoj Gupta, High Entropy Alloys, 2020
Rohit R. Shahi, Rajesh K. Mishra
Depending upon the requirements of mankind, alloys have been designed from simple to complex compositions. The resulting improvement in the performance of alloys empowered the advancement in civilization. In the past 100 years, the persistent work of researchers has led the significant evolution and progress in the area of metallic materials, which results in the invention of special alloys, such as stainless steel and superalloys. The conventional alloy design strategy relies on the mixing of one or two elements with the parent metal for the enhancement of the properties of individual elements. For example, the addition of carbon improved the strength of the steel, which showed higher strength than iron, and the addition of a small number of impurities to the ferromagnetic alloys changed their magnetic properties drastically. A shift in this conventional alloy design paradigm was encountered more than a decade ago when Cantor and co-workers [1] and Yeh and co-workers [2] independently announced the feasibility of multicomponent alloys later termed high entropy alloys (HEAs). The multi-principal element alloys (MPEAs) or high entropy alloys (HEAs) are based on multi-principal elements, which are defined in two different ways, based on composition and based on entropy [3,4]. Initially, HEAs were defined as alloys which contain at least five principal elements in equiatomic or near-equiatomic concentration (each having in the range of 5 to 35 at.%). If a minor element is added to the HEAs, their concentration should be less than 5 at.%. Later, the system was that those whose configurational entropy is greater than 1.5 R (R is the gas constant) are considered as HEA. Thus, based on the configurational entropy (∆Scon), the alloys are classified as low, medium, and high entropy alloys (as shown in Figure 18.1) [3,4].
Prediction model of elastic constants of BCC high-entropy alloys based on first-principles calculations and machine learning techniques
Published in Science and Technology of Advanced Materials: Methods, 2022
G. Hayashi, K. Suzuki, T. Terai, H. Fujii, M. Ogura, K. Sato
High-entropy alloys (HEAs) are a new class of metallic alloys composed of more than 5 different elements with equiatomic or near equiatomic composition. Following the original works of the fabrication of HEAs [1–5], significant efforts have been devoted to synthesizing HEAs and investigating their physical properties from various points of view. So far, in this new category of alloys many exceptional physical properties have been reported [6], such as high hardness and high-temperature strength [7], good temperature dependence of strength and ductility [8], thermal stability [9], high hardness and low-density refractory [10], resistances to wear, corrosion, oxidation, and fatigue [11–14], bio-compatibility [15], and even superconductivity [16]. Thus, HEAs become a new category of alloy studies and provide opportunities to explore new functional alloys.
Strengthening and fracture mechanisms of a precipitation hardening high-entropy alloy fabricated by selective laser melting
Published in Virtual and Physical Prototyping, 2022
Yaowen Wu, Xinyi Zhao, Qiang Chen, Can Yang, Mingguang Jiang, Changyong Liu, Zhe Jia, Zhangwei Chen, Tao Yang, Zhiyuan Liu
High entropy alloys (HEA) is a new class of metallic material formed by multi-principal components mixing with equal or near-equal atomic ratios. The multi-components endow the HEA with high mixing entropy to form a particular solid solution structure, which provides many excellent properties (George, Curtin, and Tasan 2020; Guo et al. 2011; Yeh et al. 2004). Distinct from conventional alloys, the discovery of HEA establishes a new alloy design philosophy; many unique characteristics unachievable before can be reached by employing the HEA design concept. Therefore, HEA has garnered lots of attention from academic and industrial fields since its discovery (Zhang et al. 2014; Yeh et al. 2004; Yuan et al. 2017; Gludovatz et al. 2014). However, a current challenge remaining in this field is the development of effective strengthening methods to overcome single-phase HEAs’ low yield strengths. Many strengthening strategies have been proposed in recent years, one of which is precipitation hardening (Yang et al. 2018, 2021; He et al. 2016; Tang et al. 2015).
A phase-field study on a eutectic high-entropy alloy during solidification
Published in Philosophical Magazine Letters, 2021
Boina Sagar, Krishanu Biswas, Rajdip Mukherjee
High-entropy alloys (HEAs) are different from conventional alloys in terms of the number of principal elements present. The former contains a minimum of four principal elements whereas there are only one or two in the latter [19]. HEAs having a single-phase solid solution are a promising class of alloys, but they lack a proper balance between strength and ductility. To tackle such problems a new class of HEAs is being developed known as eutectic high-entropy alloys (EHEAs). Eutectic alloys have better castability compared to other structures. Since the eutectic reaction is an isothermal transformation, there is no solidification range, which diminishes the problems such as compositional segregation and shrinkage cavities. The solidification behaviour of TiFeCoNiCu HEA has been previously reported as showing the presence of a eutectic structure with varying Ti/Cu molar ratio[20]. In another study a two-phase eutectic microstructure of lamellar structure was observed for the CoCrFeNiNb HEA [21]. A EHEA with lamellar structure possessing better strength and castability has been produced for the AlCoCrFeNi multicomponent system [22].