Formation and control of martensite in Ti-6Al-4V alloy produced by selective laser melting

Yang, Jyh‐Shinn; Yu, Hanchen; Yin, Junhui; Gao, Ming; Wang, Zemin; Zeng, Xiaoyan

doi:10.1016/j.matdes.2016.06.117

Cited by 679 publications

(254 citation statements)

References 33 publications

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“…They define the amount of time available for the melt to solidify at any particular instance of time [24]. The solidified high-temperature β (bcc) phase is unstable at lower temperatures and will transform (below M s ) to a metastable phase, martensitic α′ (hcp) phase by a shear-diffusion less reaction since the cooling rates in SLM are high (10 8 -10 5 K/s) [17]. Hence, the final resultant microstructure will have coarse columnar grains, which are highly oriented towards the build direction with martensite α′ inside the grains [10,17,25].…”

Section: Resultsmentioning

confidence: 99%

“…The solidified high-temperature β (bcc) phase is unstable at lower temperatures and will transform (below M s ) to a metastable phase, martensitic α′ (hcp) phase by a shear-diffusion less reaction since the cooling rates in SLM are high (10 8 -10 5 K/s) [17]. Hence, the final resultant microstructure will have coarse columnar grains, which are highly oriented towards the build direction with martensite α′ inside the grains [10,17,25]. Due to the inherent layerby-layer deposition method, as a new layer is being deposited a narrow region (heat affected zone) close to the melt pool boundary will reach temperatures above the transformation temperature (990°C), and martensite (α′) transforms back to the high-temperature β phase [12,17,25].…”

Section: Resultsmentioning

confidence: 99%

“…Hence, the final resultant microstructure will have coarse columnar grains, which are highly oriented towards the build direction with martensite α′ inside the grains [10,17,25]. Due to the inherent layerby-layer deposition method, as a new layer is being deposited a narrow region (heat affected zone) close to the melt pool boundary will reach temperatures above the transformation temperature (990°C), and martensite (α′) transforms back to the high-temperature β phase [12,17,25]. As the laser beam traverses away, the high-temperature β phase, under faster cooling conditions will transform to martensite (α′).…”

Section: Resultsmentioning

confidence: 99%

“…They described the evolution of grain (elongated) structure in the deposits due to epitaxial growth, and the fast cooling in SLM resulting in a fully martensitic phase. The martensite phase formed will experience multiple thermal cycling effects during track-by-track and layer-by-layer material deposition and therefore, finally result in a microstructure containing a hierarchical structure of martensite [17].…”

Section: Introductionmentioning

confidence: 99%

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Influence of processing parameters on the evolution of melt pool, porosity, and microstructures in Ti-6Al-4V alloy parts fabricated by selective laser melting

Dilip

Zhang

Teng³

et al. 2017

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315

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Selective laser melting involves melting and solidification of metal powder particles in a track-by-track and layer-by-layer method to fabricate 3D parts. The present investigation focuses on understanding the effect of laser power and scan speed on the evolution of melt pool, porosity and multiple thermal cycling effects on the microstructure in parts fabricated using selective laser melting. In this study, Ti-6Al-4V pre-alloyed powder was used to produce single-track deposits and bulk parts. Using different combinations of laser power and scan speeds, single-track deposits and bulk parts were produced. The cross-sections of the single-track deposits and bulk samples were prepared for metallographic observations and the melt pool shape and size and porosity were evaluated. When a low energy density was applied the un-melted powder particles produced irregularly shaped porosity, and a high energy density resulted in rounded porosity, which was due to keyhole effects. The samples produced with a proper combination of power and speeds were fully dense. Further, microstructural development under the influence of process condition was highlighted. Overall, the study demonstrates a good correlation between the single-track melt pool geometries, porosity in bulk parts and also demonstrates the microstructural inhomogeneity during deposition.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of processing parameters on the evolution of melt pool, porosity, and microstructures in Ti-6Al-4V alloy parts fabricated by selective laser melting

Dilip

Zhang

Teng³

et al. 2017

Prog Addit Manuf

315

120

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“…They were less regular than the grains fabricated via the EBM process. Optical microscope observations of the SLM fabricated samples revealed a microstructure with many parallel and perpendicular etched plates, which are denoted in the literature as an acicular α' martensite type of microstructure [74,75]. The EBM process produced a very fine needle-like α + β Widmanstätten microstructure, where the α-Ti acicular plate grains were surrounded by dark β-Ti grain boundaries.…”

Section: Light Microscopymentioning

confidence: 97%

Laser and Electron Beam Additive Manufacturing Methods of Fabricating Titanium Bone Implants

et al. 2017

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Featured Application: This work is a detailed comparison of the direct laser and electron additive manufacturing methods, which could help scientific research institutes and companies choose the best 3D printer system for the fabrication of titanium implants.Abstract: Additive Manufacturing (AM) methods are generally used to produce an early sample or near net-shape elements based on three-dimensional geometrical modules. To date, publications on AM of metal implants have mainly focused on knee and hip replacements or bone scaffolds for tissue engineering. The direct fabrication of metallic implants can be achieved by methods, such as Selective Laser Melting (SLM) or Electron Beam Melting (EBM). This work compares the SLM and EBM methods used in the fabrication of titanium bone implants by analyzing the microstructure, mechanical properties and cytotoxicity. The SLM process was conducted in an environmental chamber using 0.4-0.6 vol % of oxygen to enhance the mechanical properties of a Ti-6Al-4V alloy. SLM processed material had high anisotropy of mechanical properties and superior UTS (1246-1421 MPa) when compared to the EBM (972-976 MPa) and the wrought material (933-942 MPa). The microstructure and phase composition depended on the used fabrication method. The AM methods caused the formation of long epitaxial grains of the prior β phase. The equilibrium phases (α + β) and non-equilibrium α' martensite was obtained after EBM and SLM, respectively. Although it was found that the heat transfer that occurs during the layer by layer generation of the component caused aluminum content deviations, neither methods generated any cytotoxic effects. Furthermore, in contrast to SLM, the EBM fabricated material met the ASTMF136 standard for surgical implant applications.

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Laser‐Based Directed Energy Deposition

2023

Metal Powder–Based Additive Manufacturing

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Formation and control of martensite in Ti-6Al-4V alloy produced by selective laser melting

Cited by 679 publications

References 33 publications

Influence of processing parameters on the evolution of melt pool, porosity, and microstructures in Ti-6Al-4V alloy parts fabricated by selective laser melting

Influence of processing parameters on the evolution of melt pool, porosity, and microstructures in Ti-6Al-4V alloy parts fabricated by selective laser melting

Laser and Electron Beam Additive Manufacturing Methods of Fabricating Titanium Bone Implants

Laser‐Based Directed Energy Deposition

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