scholarly journals In-Situ Alloy Formation of a WMoTaNbV Refractory Metal High Entropy Alloy by Laser Powder Bed Fusion (PBF-LB/M)

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3095
Author(s):  
Florian Huber ◽  
Dominic Bartels ◽  
Michael Schmidt
Keyword(s):  
Electron Microscopy ◽  
Refractory Metal ◽  
High Entropy Alloy ◽  
Alloy Formation ◽  
High Entropy Alloys ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
High Entropy

High entropy or multi principal element alloys are a promising and relatively young concept for designing alloys. The idea of creating alloys without a single main alloying element opens up a wide space for possible new alloy compositions. High entropy alloys based on refractory metals such as W, Mo, Ta or Nb are of interest for future high temperature applications e.g., in the aerospace or chemical industry. However, producing refractory metal high entropy alloys by conventional metallurgical methods remains challenging. For this reason, the feasibility of laser-based additive manufacturing of the refractory metal high entropy alloy W20Mo20Ta20Nb20V20 by laser powder bed fusion (PBF-LB/M) is investigated in the present work. In-situ alloy formation from mixtures of easily available elemental powders is employed to avoid an expensive atomization of pre-alloyed powder. It is shown that PBF-LB/M of W20Mo20Ta20Nb20V20 is in general possible and that a complete fusion of the powder mixture without a significant number of undissolved particles is achievable by in-situ alloy formation during PBF-LB/M when selecting favorable process parameter combinations. The relative density of the samples with a dimension of 6 × 6 × 6 mm3 reaches, in dependence of the PBF-LB/M parameter set, 99.8%. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements confirm the presence of a single bcc-phase. Scanning electron microscopy (SEM) images show a dendritic and/or cellular microstructure that can, to some extent, be controlled by the PBF-LB/M parameters.

scholarly journals In Situ Formation of a Metastable β-Ti Alloy by Laser Powder Bed Fusion (L-PBF) of Vanadium and Iron Modified Ti-6Al-4V

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1067 ◽  
Author(s):  
Florian Huber ◽  
Thomas Papke ◽  
Christian Scheitler ◽  
Lukas Hanrieder ◽  
Marion Merklein ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Homogeneous Element ◽  
Alloy Formation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Β Phase ◽  
Stabilizing Effect

The aim of this work is to investigate the β-Ti-phase-stabilizing effect of vanadium and iron added to Ti-6Al-4V powder by means of heterogeneous powder mixtures and in situ alloy-formation during laser powder bed fusion (L-PBF). The resulting microstructure was analyzed by metallographic methods, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were characterized by compression tests, both prior to and after heat-treating. Energy dispersive X-ray spectroscopy showed a homogeneous element distribution, proving the feasibility of in situ alloying by LPBF. Due to the β-phase-stabilizing effect of V and Fe added to Ti-6Al-4V, instead of an α’-martensitic microstructure, an α/β-microstructure containing at least 63.8% β-phase develops. Depending on the post L-PBF heat-treatment, either an increased upsetting at failure (33.9%) compared to unmodified Ti-6Al-4V (28.8%), or an exceptional high compressive yield strength (1857 ± 35 MPa compared to 1100 MPa) were measured. The hardness of the in situ alloyed material ranges from 336 ± 7 HV0.5, in as-built condition, to 543 ± 13 HV0.5 after precipitation-hardening. Hence, the range of achievable mechanical properties in dependence of the post-L-PBF heat-treatment can be significantly expanded in comparison to unmodified Ti-6Al-4V, thus providing increased flexibility for additive manufacturing of titanium parts.

scholarly journals Synchrotron Characterisation of Ultra-Fine Grain TiB2/Al-Cu Composite Fabricated by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Sheng Li ◽  
Biao Cai ◽  
Ranxi Duan ◽  
Lei Tang ◽  
Zihan Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Tensile Loading ◽  
Fusion Pore ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
Random Texture ◽  
Average Grain Size

AbstractIsotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.

Compositionally graded AlxCoCrFeNi high-entropy alloy manufactured by laser powder bed fusion

Materialia ◽  
2021 ◽  
pp. 101308
Author(s):  
Fengxia Wei ◽  
Siyuan Wei ◽  
Kwang Boon Lau ◽  
Wei Hock Teh ◽  
Jing Jun Lee ◽  
...  
Keyword(s):  
High Entropy Alloy ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
High Entropy

scholarly journals Printability and microstructure of the CoCrFeMnNi high-entropy alloy fabricated by laser powder bed fusion

2018 ◽  
Vol 224 ◽  
pp. 22-25 ◽  
Author(s):  
A. Piglione ◽  
B. Dovgyy ◽  
C. Liu ◽  
C.M. Gourlay ◽  
P.A. Hooper ◽  
...  
Keyword(s):  
High Entropy Alloy ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
High Entropy

scholarly journals Laser Powder Bed Fusion (PBF-LB/M) Process Strategies for In-Situ Alloy Formation with High-Melting Elements

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 336
Author(s):  
Florian Huber ◽  
Michael Rasch ◽  
Michael Schmidt
Keyword(s):  
Homogeneous Element ◽  
Alloying Elements ◽  
Complete Fusion ◽  
Alloy Formation ◽  
Powder Bed Fusion ◽  
High Melting ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Process Strategy

In-situ alloy formation by Laser Powder Bed Fusion (PBF-LB/M) from mixtures of easily available elemental powders is an appealing approach for developing and qualifying new alloys for laser based additive manufacturing of metals. However, especially when dealing with high-melting elements, like W, Ta, Mo, or Nb, it is difficult to achieve a homogeneous element distribution and a complete fusion of the powder particles. The aim of this work was to understand the effects of the PBF-LB/M process parameters (laser power, scan speed, laser spot diameter) and three different single- and double-exposure strategies on the fusion of high-melting W, Ta, Mo, and Nb particles in a Ti-matrix. For this purpose, 220 samples with 10 vol.% of the high-melting particle fraction were prepared and analyzed by optical light microscopy and automated image processing, as well as by scanning electron microscopy (SEM). The results are discussed in the context of current research on the process dynamics of PBF-LB/M. Based on that process strategies to support a complete fusion of high-melting particles during in-situ alloy formation are derived. It is shown that the number of unmolten particles can be at least decreased by a factor of ten compared to the most unfavorable parameter combination. For the lower melting elements, Nb and Mo, a complete fusion without any remaining particles visible in the microsections was achieved for certain parameter combinations. The results prove the feasibility of in-situ alloy formation with high-melting alloying elements, but they also demonstrate the necessity to adjust the PBF-LB/M process strategy to achieve a complete dissolution of the alloying elements.

Bimetal printing of high entropy alloy/metallic glass by laser powder bed fusion additive manufacturing

2022 ◽  
Vol 141 ◽  
pp. 107430
Author(s):  
Hao Wang ◽  
Junquan Chen ◽  
Hailu Luo ◽  
Di Wang ◽  
Changhui Song ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Metallic Glass ◽  
High Entropy Alloy ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
High Entropy
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