Getting tougher in the ultracold

Description Certain alloys show exceptional toughness in a liquid helium environment The disastrous accident of the Titanic in 1912 occurred when the British ocean liner struck an iceberg and sank. Insufficient fracture resistance of the ship’s steel at low temperature ensured the ship’s demise (1). Thereafter, selection of materials with excellent cryogenic toughness became an important prerequisite for low-temperature, load-bearing applications. Despite progress in the understanding of fracture mechanics, most metallic materials show reduced toughness with decreasing temperatures (2), especially in the realm of the temperature of liquid helium (−269°C; 4.15 K). Thus, searching for tough alloys in cryogenic temperatures has remained a challenge. On page 978 of this issue, Liu et al. (3) report that certain alloys containing the metals chromium (Cr), cobalt (Co), and nickel (Ni) show exceptional fracture toughness at 20 K and attribute this property to a sequence of deformation mechanisms. These metal mixtures could potentially be used for applications in especially low temperatures, such as deep-space exploration (4).