Lowering the ductile-to-brittle transition temperature to -36 °C via fine-grained structures in chromium

The inherent ductile-to-brittle transition (DBT) behavior of body-centered cubic (BCC) metals severely limits their applications, and leads to low-temperature brittleness. To enhance the low temperature toughness of BCC metals, we take chromium as an example and design a fine-grained structure with average grain size of 5 μm, which shows a substantial decrease of DBT temperature to -36 °C. Compared with other samples with larger average grain sizes (45–135 μm), the fine-grained chromium still exhibits excellent toughness at -20 °C, and has the highest fracture energy and the yielding load. Our results reveal that numerous grain boundaries act as dislocation sources to emit easy glide edge dislocations at low temperature and also effectively slow down crack propagation, all together toughen ambient brittle chromium.