Abstract
High-entropy alloys (HEAs) are a novel class of alloys that have many desirable properties. The serrated flow that occurs in high-entropy alloys during mechanical deformation is an important phenomenon since it can lead to significant changes in the microstructure of the alloy. In this article, we review the recent findings on the serration behavior in a variety of high-entropy alloys. Relationships among the serrated flow behavior, composition, microstructure, and testing condition are explored. Importantly, the mechanical-testing type (compression/tension), testing temperature, applied strain rate, and serration type for certain high-entropy alloys are summarized. The literature reveals that the serrated flow can be affected by experimental conditions such as the strain rate and test temperature. Furthermore, this type of phenomenon has been successfully modeled and analyzed, using several different types of analytical methods, including the mean-field theory formalism and the complexity-analysis technique. Importantly, the results of the analyses show that the serrated flow in HEAs consists of complex dynamical behavior. It is anticipated that this review will provide some useful and clarifying information regarding the serrated-flow mechanisms in this material system. Finally, suggestions for future research directions in this field are proposed, such as the effects of irradiation, additives (such as C and Al), the presence of nanoparticles, and twinning on the serrated flow behavior in HEAs.
Highlights
A clear summary of the serrated flow phenomenon, as it occurs in High-entropy alloys (HEAs), was provided
In terms of the microstructure, serrations typically occur due to either twinning mechanisms or dislocation pinning by solute atoms at temperatures of room temperature (RT) and above
The results of the analyses indicated that the serrated flow in HEAs consist of complex dynamical behavior
Summary
High-entropy alloys (HEAs) are an important class of materials that emerged in the earlier part of this century [1,2]. It is commonly accepted that the high-entropy effect explains why HEAs often are observed to form only one or two primary phases, while the Gibbs’s phase rule indicates that they could form five or more phases [13,14,15,16] This effect corresponds to a relatively lower Gibbs free energy of mixing for the solid-solution phases in the alloy, as determined by the following equation [13,14,15]:. The random distribution of elements (and lattice-potential energy) in the alloy may be a contributing factor to the sluggish diffusion of atoms and vacancies to lattice sites of lower energies [13,19] This sluggish diffusion effect results in the potential beneficial properties of slower grain growth [2], exceptional elevated-temperature stability [20], high-temperature strength [21], and a higher recrystallization temperature. Reference [68] with permission)
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