scholarly journals Microstructure and properties of TiB2-reinforced Ti–35Nb–7Zr–5Ta processed by laser-powder bed fusion

2021 ◽  
Author(s):  
Rodolfo Lisboa Batalha ◽  
Vitor Eduardo Pinotti ◽  
Omar O. S. Alnoaimy ◽  
Weverson Capute Batalha ◽  
Tobias Gustmann ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Martensitic Transformation ◽  
Biomedical Applications ◽  
Solidification Structure ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Promising Alternative ◽  
Recoverable Strain ◽  
Powder Bed ◽  
Β Phase

AbstractThe Ti–35Nb–7Zr–5Ta (wt%, TNZT) alloy was reinforced with TiB2 and synthesized by L-PBF. The relatively small TiB2 particles change the solidification structure from cellular to columnar-dendritic and lead to submicron TiB precipitation in the β matrix. This results in pronounced grain refinement and reduction of texture. However, the microstructure of the additively manufactured TNZT-TiB2 is still different from the as-cast, unreinforced TNZT, which contains equiaxed and randomly oriented grains. The β phase is less stable in the as-cast samples, leading to stress-induced martensitic transformation and recoverable strain of 1.5%. The TNZT with 1 wt% of TiB2 presents significantly higher compressive strength (σYS = 495 MPa) compared to unreinforced samples (σYS = 430 MPa), without sacrificing ductility or altering Young’s modulus (E ≈ 46 GPa). The addition of a small fraction of TiB2 to the TNZT alloy synthesized by L-PBF is a promising alternative for manufacturing sophisticated components for biomedical applications. Graphical abstract

scholarly journals Comparison of Phase Characteristics and Residual Stresses in Ti-6Al-4V Alloy Manufactured by Laser Powder Bed Fusion (L-PBF) and Electron Beam Powder Bed Fusion (EB-PBF) Techniques

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 796
Author(s):  
Aya Takase ◽  
Takuya Ishimoto ◽  
Naotaka Morita ◽  
Naoko Ikeo ◽  
Takayoshi Nakano
Keyword(s):  
Electron Beam ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Process Parameters ◽  
Phase Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Solidification Temperature ◽  
Powder Bed ◽  
Β Phase

Ti-6Al-4V alloy fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF) techniques have been studied for applications ranging from medicine to aviation. The fabrication technique is often selected based on the part size and fabrication speed, while less attention is paid to the differences in the physicochemical properties. Especially, the relationship between the evolution of α, α’, and β phases in as-grown parts and the fabrication techniques is unclear. This work systematically and quantitatively investigates how L-PBF and EB-PBF and their process parameters affect the phase evolution of Ti-6Al-4V and residual stresses in the final parts. This is the first report demonstrating the correlations among measured parameters, indicating the lattice strain reduces, and c/a increases, shifting from an α’ to α+β or α structure as the crystallite size of the α or α’ phase increases. The experimental results combined with heat-transfer simulation indicate the cooling rate near the β transus temperature dictates the resulting phase characteristics, whereas the residual stress depends on the cooling rate immediately below the solidification temperature. This study provides new insights into the previously unknown differences in the α, α’, and β phase evolution between L-PBF and EB-PBF and their process 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.

Laser Powder Bed Fusion: tailoring the microstructure of alloys for biomedical applications

2019 ◽  
Vol 19 ◽  
pp. 24-32
Author(s):  
E. Santecchia ◽  
P. Mengucci ◽  
A. Gatto ◽  
E. Bassoli ◽  
L. Denti ◽  
...  
Keyword(s):  
Biomedical Applications ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications

JOM ◽  
2017 ◽  
Vol 70 (3) ◽  
pp. 372-377 ◽  
Author(s):  
I. Yadroitsev ◽  
P. Krakhmalev ◽  
I. Yadroitsava ◽  
A. Du Plessis
Keyword(s):  
Biomedical Applications ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

scholarly journals Influence of Powder Bed Temperature on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Fabricated via Laser Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2278
Author(s):  
Lei-Lei Xing ◽  
Wen-Jing Zhang ◽  
Cong-Cong Zhao ◽  
Wen-Qiang Gao ◽  
Zhi-Jian Shen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Β Phase ◽  
Phase Precipitate ◽  
Bed Temperature ◽  
Martensitic Microstructure ◽  
Increasing Temperature

Laser powder bed fusion (LPBF) is being increasingly used in the fabrication of complex-shaped structure parts with high precision. It is easy to form martensitic microstructure in Ti-6Al-4V alloy during manufacturing. Pre-heating the powder bed can enhance the thermal field produced by cyclic laser heating during LPBF, which can tailor the microstructure and further improve the mechanical properties. In the present study, all the Ti-6Al-4V alloy samples manufactured by LPBF at different powder bed temperatures exhibit a near-full densification state, with the densification ratio of above 99.4%. When the powder bed temperature is lower than 400 °C, the specimens are composed of a single α′ martensite. As the temperature elevates to higher than 400 °C, the α and β phase precipitate at the α′ martensite boundaries by the diffusion and redistribution of V element. In addition, the α/α′ lath coarsening is presented with the increasing powder bed temperature. The specimens manufactured at the temperature lower than 400 °C exhibit high strength but bad ductility. Moreover, the ultimate tensile strength and yield strength reduce slightly, whereas the ductility is improved dramatically with the increasing temperature, when it is higher than 400 °C.

scholarly journals Solid-State Phase Transformations in Thermally Treated Ti–6Al–4V Alloy Fabricated via Laser Powder Bed Fusion

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2876
Author(s):  
Paolo Mengucci ◽  
Eleonora Santecchia ◽  
Andrea Gatto ◽  
Elena Bassoli ◽  
Antonella Sola ◽  
...  
Keyword(s):  
Solid State ◽  
Phase Transformations ◽  
Xrd Analysis ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
X Ray Diffraction ◽  
Powder Bed ◽  
Β Phase ◽  
Transmission Electron ◽  
Scanning Transmission

Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti–6Al–4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron diffraction (ND), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α’ martensite of the as-produced (#AP) sample. The retained β was not detectable by XRD analysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element diffusion and partitioning are the main mechanisms in the α ↔ β transformation that causes lattice expansion during heating and determines the final shape and size of phases. The retained β phase plays a key role in the α’ → β transformation kinetics.

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