Metal Alloys for Fusion‐Based Additive Manufacturing

Abstract

Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts incrementally layer by layer. Thus, metal AM has inherent advantages in part complexity, time, and waste saving. However, due to its complex thermal cycle and rapid solidification during processing, the alloys well suit and commercially used for metal AM today are limited. Therefore, it is important to understand the alloying strategy and current progress with materials performance to consider alloy development for metal AM. This review presents the current range of alloys available for metal AM, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys, and low melting point alloys), and compositionally complex alloys (including bulk metallic glasses and high entropy alloys) with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system. In addition, some promising alloy systems for metal AM are highlighted. Approaches for designing and optimizing new materials for metal AM have been summarized.

Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion

“…of the cellular dendrites microstructure of 316 L steel manufactured by LPBF were consistent with previous reports [5][6][7][18][19][20][21][22]. XRD, EBSD, and TEM analysis carried out in the present investigation revealed a fully austenitic structure in the LPBF 316 L steel.…”

“…Not all newly nucleated colonies had the same color as the adjacent grains in the substrate, meaning that that not all substrate grains satisfied the conditions for epitaxial nucleation. Similar epitaxial nucleation between the layers was observed by EBSD in different AM materials [5][6][7]25,26]. Figure 2c also shows that in many colonies, the orientation in the inner region was generally the same.…”

“…In the laser powder fusion processes, the cellular or cellular-dendritic mode was not uncommon. This type of microstructure has been observed for different engineering alloys like austenitic steels, aluminum alloys Co-Cr, and nickel base alloys [5][6][7][10][11][12][13][14][15][16][17][18][19][20][21][22] manufactured by laser or electron powder bed fusion methods. At the high solidification rates observed in the PBF processes, a solute-rich boundary layer is built up in front of the solid-liquid interface due to the limited solute atom diffusion in the liquid phase, thus approaching the conditions for constitutional supercooling [27].…”

“…Quite remarkable variations of yield strength (300-600 MPa), ultimate tensile strength (350-650 MPa), and elongation (10-60%) are usually observed [5,6,[18][19][20][21]29,36,44,46,47]. Higher strength could be associated with fine structure, high dislocation density, cellular structure, and the presence of nanoparticles.…”

“…A lower elongation in LPBF material is associated with high strength; additionally, porosity and internal defects contribute to a large scatter in elongation values. A summary of the mechanical characteristics of LPBF 316 L steel can be found in [5,6,44]. Figure 8 illustrates the dependence of the hardness of AM and conventional 316 L steel on the inversed square root of primary cell spacing.…”