Research progress on high-entropy alloys for extreme loading environments

High-entropy alloys（HEAs）have attracted considerable attention from the research community as a pioneering alloy design paradigm over the past two decades. They have fundamentally challenged traditional design paradigms and exhibited exceptional mechanical properties and functional characteristics，thereby positioning themselves as promising candidates for significant engineering applications in the future. Recent advancements have unveiled several alloy systems that demonstrate exceptional performance across diverse metrics，including low-temperature fracture toughness，high-temperature strength，impact resistance，radiation tolerance，and fatigue resistance. These qualities render HEAs highly attractive materials for research with substantial application potential in critical domains such as deep space exploration，deep-sea investigations，low-temperature superconductivity，and advanced nuclear energy technologies. This paper will briefly introduce the concept and classification of HEAs，and review the experimental progress of HEAs under various extreme conditions such as extremely low temperatures，high-speed impacts，and high nuclear radiation. We also summarize the strategies for enhancing the strength and toughness of HEAs，and extract the deformation mechanisms and physical and chemical properties of HEAs under different extreme loads. It is foreseeable that the main development direction of HEAs will be to form microscopic fluctuations in chemical composition and construct multi-scalestructural ordering efficiently through fine adjustment of the selection and proportion of alloying elements and optimization of heat treatment processes. For comprehensive studies on HEAs subjected to extreme loads，it is essential to explore their microscopic deformation mechanisms further while proposing innovative strategies designed to address inherent trade-offs between strength and toughness. The integration of state-of-the-art simulation techniques combined with advanced characterization methods will be crucial for improving research efficiency while providing insights into microstructural behavior. Additionally，tailored optimization approaches should be implemented for distinct advantageous systems and phase structures，particularly those capable of activating dislocation movements，twinning，phase transformations and incorporating novel processing methodologies such as additive manufacturing. Finally，conducting more realistic simulation experiments that closely replicate extreme environments along with generating relevant engineering data are vital steps toward accelerating the practical application of HEAs in challenging settings.