High-entropy alloys (HEAs), as a new class of materials, are nearly equiatomic and multi-element systems, which can crystallize as a single phase or multi-phases. Most of the HEAs described in the literature contain multiple phases (secondary phases, nanoparticles, and so on), rather than a single solid-solution phase. Thus, it is essential to review the typical mechanical properties of both single-phase and multiphase HEAs thoroughly, with emphases on (1) the fundamental physical mechanisms and (2) the difference from conventional alloys. In this paper, mainly based on different mechanical properties, HEAs are classified into four types for the first time, i.e., (a) HEA alloy systems of 3d-transition metals only (Type 1), (b) HEA alloy systems of transition metals with larger atomic-radius elements (Type 2), (c) HEA alloy systems of refractory metals (Type 3), and (4) others (Type 4). Then a number of aspects of mechanical behavior are reviewed and discussed, including the elastic anisotropy, yield strength, high-temperature performance, serration behavior, fracture toughness, and fatigue responses, which may serve as a demonstrative summary for the current progress in the scientific research of HEAs. Several mechanisms that quantitatively explain the mechanical properties of single-phase and multiphase HEAs in terms of basic defects (dislocations, twinning, precipitates, etc.) are discussed. A number of future research activities are suggested, based on the emphasis on developing high-performance structural materials. The review concludes with a brief summary of major mechanical properties and insights into the deformation behavior of single-phase and multiphase HEAs. The comparison and contrast between HEAs and conventional alloys remain the most compelling motivation for future studies. With the integrated experimental and simulation investigations, a clearer picture of the fundamental deformation behavior of single-phase and multiphase HEAs could be explored.

高熵合金（HEA）作为一类新型材料，几乎是等原子和多元素的系统，可以结晶为单相或多相。文献中描述的大多数HEA包含多个阶段（次级阶段，纳米粒子等），而不是单个固溶阶段。因此，有必要彻底审查单相和多相HEA的典型机械性能，重点是（1）基本物理机理和（2）与常规合金的区别。本文主要基于不同的机械性能，首次将HEA分为四种类型，即（a）仅3d过渡金属的HEA合金体系（类型1），（b）过渡金属的HEA合金体系具有较大的原子半径元素（类型2），（c）难熔金属的HEA合金体系（类型3），以及其他（4）种（类型4）。然后回顾并讨论了力学行为的许多方面，包括弹性各向异性，屈服强度，高温性能，锯齿行为，断裂韧性和疲劳响应，这些可以作为科学界当前进展的例证性总结。 HEA的研究。讨论了从基本缺陷（位错，孪晶，沉淀物等）的角度定量解释单相和多相HEA力学性能的几种机理。在强调开发高性能结构材料的基础上，提出了许多未来的研究活动。综述以主要力学性能的简要总结以及对单相和多相HEA的变形行为的见解作为结束。HEA与常规合金之间的比较和对比仍然是未来研究的最有说服力的动机。通过综合的实验和仿真研究，可以更清楚地了解单相和多相HEA的基本变形行为。