Abstract
Fascinated by the exceptional mechanical properties of high entropy alloys (HEAs), unremitting endeavors are placed on accelerating their engineering applications in multiple critical fields. As all other structural materials, attaining sufficient fracture resistance is a vital requirement for HEAs, particularly for safety critical applications. Along this line, the fracture resistance of a number of HEAs and medium-entropy alloys (MEAs) had been studied in the past decade. While some exhibit unprecedented fracture toughness akin to the toughest materials ever known, others are just alike brittle materials. Herein, we summarize one decade of investigations of the fracture resistance of HEAs and MEAs, including the characterization of fracture toughness, disclosure of fractographic characteristics, and understanding of fracture micro-mechanisms. The role of alloy composition, temperature, phase constituent, and characterization techniques in altering the fracture toughness are discussed; characteristics of the cleavage and shear fractures are detailed; toughening and weakening mechanisms, from the atomic to the defect level, are reviewed. In the end, some key questions are raised, and the directions for future research are suggested.
