Additive Manufacturing of Advanced Multi‐Component Alloys: Bulk Metallic Glasses and High Entropy Alloys

Abstract

Bulk metallic glasses (BMGs) and high entropy alloys (HEAs) are both important multi-component alloys with novel microstructures and unique properties, which make them promising for applications in many industries. However, certain hindrances have been identified in the fabrication of BMGs and HEAs by conventional techniques due to the intrinsic requirements of BMGs and HEAs. With the advent of metal additive manufacturing, new opportunities have been perceived to fabricate geometrically complex BMGs and HEAs with tailorable microstructure theoretically at any site within the specimen, which are not achievable using conventional fabrication techniques. After providing some background and introducing the conventional fabrication techniques for BMGs and HEAs, this review will focus on the current status, development, and challenges in metal additive manufacturing of BMGs and HEAs including different additive manufacturing techniques being used, microstructure design and evolution, as well as properties of the fabricated BMGs and HEAs. A future outlook of metal additive manufacturing of BMGs and HEAs will also be provided at the end.

Laser‐Based Additive Manufacturing Technologies for Aerospace Applications

“…[218] Parts may contain site-specific properties, layered dissimilar compositions, gradually transitioned dissimilar alloys, [98] composite structures, [165] the same alloy with different crystals or microstructures, or the same alloys with different densities/porosities. AM technology, particularly the direct laser powder deposition process, also provides an opportunity for engineering new materials such as MAX phases, [117] bulk metallic glasses [220] and HEAs [221] for their exceptional properties. Composite materials with more than one distinctive phase produced using AM [219] include metal/ceramic, polymer/ceramic, or ceramic/ ceramic.…”

“…Composite materials with more than one distinctive phase produced using AM [219] include metal/ceramic, polymer/ceramic, or ceramic/ ceramic. [220] The advent of AM technology makes it possible to design and create complex HEA parts directly from an elemental powder mixture, with enhanced composition homogeneity and finer microstructure. As with most of the new technology development with large investment, information is kept in house within private organizations and is not available to the public domain.…”

“…Researchers must play a role in disseminating results to the public by investigating new AM materials, materials with tailored properties, and their resulting microstructures. AM technology, particularly the direct laser powder deposition process, also provides an opportunity for engineering new materials such as MAX phases, [117] bulk metallic glasses [220] and HEAs [221] for their exceptional properties. In particular, HEAs (usually with five principal elements in equimolar/equiatomic compositions, such as CoCrCuFeNi and low-density MgAlCuMnZn and AlLiMgScTi) [222] have emerged as potential replacements for existing superalloys due to their phase stability, high strength/ductility, and environmental resistance.…”

“…In particular, HEAs (usually with five principal elements in equimolar/equiatomic compositions, such as CoCrCuFeNi and low-density MgAlCuMnZn and AlLiMgScTi) [222] have emerged as potential replacements for existing superalloys due to their phase stability, high strength/ductility, and environmental resistance. [220] The advent of AM technology makes it possible to design and create complex HEA parts directly from an elemental powder mixture, with enhanced composition homogeneity and finer microstructure. In fact, pioneer research [223,224] has shown that using DLD, HEA alloys with selected compositions can be fabricated with added advantages of less segregation, reduced brittle phases, and grain refinement.…”

Multi-Material Design in Welding Arc Additive Manufacturing

“…For this purpose, different materials are specifically combined with each other in order to adjust local mechanical properties to the anticipated load. In addition, to conventional alloying systems, novel material concepts such as high-entropy alloys are increasingly being used in additive manufacturing [8].…”