Toward damage-tolerant bulk metallic glasses: Fracture behavior and brittle–ductile transition

In order to replace the conventional alloys with bulk metallic glasses (BMGs), studies have been actively conducted to investigate the mechanical characteristics of BMGs in various aspects. One of the major ongoing issues is process-related variations in key properties such as fracture toughness. Although there is still a lack of knowledge on how to prevent catastrophic failure in most BMGs, Griffith’s theory, modified by Irwin and Orowan, allows us to understand that the dissipation of plastic energy by atomic rearrangement within the shear band is a key factor in designing damage-tolerant BMGs by preventing crack opening. In this article, we discuss the fracture behavior of BMGs in relation to Griffith’s theory and review studies that examined how intrinsic and extrinsic factors, such as alloy composition, temperature, sample size, and strain rate affect the brittle–ductile transitions in BMGs. As several BMGs recently reported excellent fracture toughness similar to that of ductile alloys such as conventional low-carbon steels, damage-tolerant BMGs will be a new class of high-performance structural engineering materials with significant technological strengths. Graphical abstract