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15 pages, 8008 KiB

Open AccessArticle

Control of Density and Grain Structure of a Laser Powder Bed-Fused Superelastic Ti-18Zr-14Nb Alloy: Simulation-Driven Process Mapping

by Vladimir Brailovski, Victoria Kalinicheva, Morgan Letenneur, Konstantin Lukashevich, Vadim Sheremetyev and Sergey Prokoshkin

Metals 2020, 10(12), 1697; https://doi.org/10.3390/met10121697 - 21 Dec 2020

Cited by 18 | Viewed by 3726

Abstract

This study focuses on the control of density and grain structure of a superelastic Ti-18Zr-14Nb (at. %) alloy subjected to laser powder bed fusion. It starts with the production and characterization of a Ti-18Zr-14Nb powder feedstock and printing of a series of calibration specimens. These specimens are next subjected to chemical, structural, phase and texture analyses in order to collect experimental data needed to build simulation-driven processing maps in the laser energy density–material build rate coordinates. The results of this study prove that, once calibrated, the simulation-driven processing maps can be used to relate the main LPBF parameters (laser power, scanning speed, hatching distance and layer thickness) to the density and grain structure of the printed material, and the process productivity (build rate). Even though this demonstration is made for a specific material–system combination (TiNbZr & TruPrint 1000), such a process mapping is feasible for any material–system combination and can, therefore, be exploited for the process optimization purposes and for manufacturing of functionally graded materials or parts with intentionally seeded porosity. Full article

(This article belongs to the Special Issue Shape Memory Alloys 2020)

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13 pages, 10711 KiB

Open AccessCommunication

Laser Powder Bed Fusion with Intentionally-Seeded Porosity for Prototyping of Powder Metallurgy Parts

by Morgan Letenneur, Pete Imbrogno, Amin Molavi-Kakhki and Vladimir Brailovski

J. Manuf. Mater. Process. 2020, 4(4), 119; https://doi.org/10.3390/jmmp4040119 - 11 Dec 2020

Cited by 5 | Viewed by 4047

Abstract

Laser powder bed fusion (LPBF) additive manufacturing technology was used to produce functional prototypes of powder metallurgy (PM) components from high carbon content, iron-based water-atomized powders. The melt pool modeling and design of experiment approaches were combined in order to determine the LPBF operation window allowing to print parts with components similar to the PM in terms of density, microstructure and mechanical properties. The size, morphology and distribution of processing-induced pores were evaluated using computed tomography, while a microstructure analysis was carried out using X-ray diffraction and scanning electron microscopy, and the mechanical properties were evaluated using tensile and unnotched Charpy testing. It was demonstrated that LPBF technology could effectively be used for the just-in-time manufacture of high-fidelity functional prototypes of PM parts from iron-based powders. Full article

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17 pages, 62932 KiB

Open AccessFeature PaperArticle

The Average Grain Size and Grain Aspect Ratio in Metal Laser Powder Bed Fusion: Modeling and Experiment

by Morgan Letenneur, Alena Kreitcberg and Vladimir Brailovski

J. Manuf. Mater. Process. 2020, 4(1), 25; https://doi.org/10.3390/jmmp4010025 - 11 Mar 2020

Cited by 17 | Viewed by 6696

Abstract

The additive manufacturing (AM) process induces high uncertainty in the mechanical properties of 3D-printed parts, which represents one of the main barriers for a wider AM processes adoption. To address this problem, a new time-efficient microstructure prediction algorithm was proposed in this study for the laser powder bed fusion (LPBF) process. Based on a combination of the melt pool modeling and the design of experiment approaches, this algorithm was used to predict the microstructure (grain size/aspect ratio) of materials processed by an EOS M280 LPBF system, including Iron and IN625 alloys. This approach was successfully validated using experimental and literature data, thus demonstrating its potential efficiency for the optimization of different LPBF powders and systems. Full article

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13 pages, 4093 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Laser Powder Bed Fusion Processing Using a Combination of Melt Pool Modeling and Design of Experiment Approaches: Density Control

by Morgan Letenneur, Alena Kreitcberg and Vladimir Brailovski

J. Manuf. Mater. Process. 2019, 3(1), 21; https://doi.org/10.3390/jmmp3010021 - 21 Feb 2019

Cited by 91 | Viewed by 11943

Abstract

A simplified analytical model of the laser powder bed fusion (LPBF) process was used to develop a novel density prediction approach that can be adapted for any given powder feedstock and LPBF system. First, calibration coupons were built using IN625, Ti64 and Fe powders and a specific LPBF system. These coupons were manufactured using the predetermined ranges of laser power, scanning speed, hatching space, and layer thickness, and their densities were measured using conventional material characterization techniques. Next, a simplified melt pool model was used to calculate the melt pool dimensions for the selected sets of printing parameters. Both sets of data were then combined to predict the density of printed parts. This approach was additionally validated using the literature data on AlSi10Mg and 316L alloys, thus demonstrating that it can reliably be used to optimize the laser powder bed metal fusion process. Full article

(This article belongs to the Special Issue Anniversary Feature Papers)

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17 pages, 7464 KiB

Open AccessArticle

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

by Morgan Letenneur, Vladimir Brailovski, Alena Kreitcberg, Vladimir Paserin and Ian Bailon-Poujol

J. Manuf. Mater. Process. 2017, 1(2), 23; https://doi.org/10.3390/jmmp1020023 - 17 Dec 2017

Cited by 53 | Viewed by 9006

Abstract

The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical low-cost water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine—in a first approximation—the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm³/h, and a volumetric energy density ranging from 50 to 190 J/mm³, was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm³ and a build rate of 9 cm³/h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used. Full article

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