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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. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) was used to manufacture fully martensitic (β′ 1 ) samples of the shape-memory alloy 81.95Cu-11.85Al-3.2Ni-3Mn (wt%). Crack-free specimens with a high relative density of about 98.9 ± 0.1% were produced. Immediate remelting of already processed layers during SLM enhances the relative density (99.5 ± 0.3%). Primarily by varying the scanning speed in the remelting step, the thickness of the remelted zone can be adjusted. Moreover, remelting alters the microstructure as well as the transformation temperatures, which tend to rise with the volumetric energy input. In this way, the shape-memory properties can be modified without compromising the relative density and the considerable plasticity of the samples. Thus, the remelting procedure proves to be an interesting tool for 81.95Cu-11.85Al-3.2Ni-3Mn and related alloys in order to optimize and tailor their performance already during SLM processing and without applying additional post-processing steps. [ABSTRACT FROM AUTHOR]

The Ti-based bulk metallic glass Ti 47 Cu 38 Zr 7.5 Fe 2.5 Sn 2 Si 1 Ag 2 was fabricated by selective laser melting (SLM). The crystalline phases in the gas-atomized powder disappear after additive manufacturing and the SLM parts are fully glassy. All SLM samples reach a high relative density above 98.5% and a high compressive strength around 1700 MPa despite failing prematurely in comparison with as-cast rods. Our work identifies a Ti-based glass-forming alloy suitable for laser-based additive manufacturing and opens up new vistas for overcoming the intrinsic limitations of Ti-based BMGs in terms of size and geometry and for making them accessible to (biomedical) applications. [ABSTRACT FROM AUTHOR]