3D printing of bulk metallic glasses

Bulk metallic glasses (BMGs) being metallic materials without long-range order have attracted a considerable amount of interest from academia and industry in the past three decades due to their unique and outstanding properties. However, the manufacturing of glassy components with large dimension and complex geometries has remained a considerable challenge. The main obstructions in this regard arise from the oftentimes limited glass-forming ability (GFA) of most metallic systems, which requires extremely fast quenching of the corresponding melts and, consequently, limits the obtainable dimensions. In addition, BMGs generally have a poor machinability due to their intrinsic high hardness and extreme brittleness. The emerging 3D printing technology (also called additive manufacturing), as an advanced bottom-up manufacturing process, seems to be a viable route to circumvent these deficiencies inherent to conventional processing routes. Additive manufacturing theoretically allows the fabrication of large-sized BMGs and components with complex geometries, greatly extending the range of applications of BMGs as both structural and functional materials. The 3D printing technology has given fresh impetus to the field of BMGs and represents an approach, which is intensely explored in the BMG’s scientific community at the moment. In this review, we present a comprehensive overview of the state-of-the-art research on various aspects related to 3D printing of BMGs. It covers various 3D printing techniques for manufacturing BMGs, the microstructures (e.g. structural heterogeneities and fused-related defects) found in 3D-printed BMGs, the crystallization behavior in additively manufactured glasses and the associated alloy selection criterion, the observed mechanical properties and deformation mechanisms, and finally the functional properties and potential applications of 3D-printed BMGs and BMG matrix composites, in terms of catalysis, wear, corrosion, and biocompatibility. This article also identifies a number of key questions to be answered in the future in this important research direction in order to successfully bridge the gap from fundamental research to large-scale application of additively manufactured bulk metallic glasses.