Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting

Barriobero-Vila, Pere; Artzt, Katia; Stark, Andreas; Schell, Norbert; Siggel, Martin; Gussone, Joachim; Kleinert, Jan; Kitsche, Wolfgang; Requena, Guillermo; Haubrich, Jan

doi:10.1016/j.scriptamat.2020.02.043

Cited by 40 publications

(27 citation statements)

References 10 publications

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“…Mapping of melt pool data on the build-plane can reveal the typical phenomenon of overheating of “overhang” structures above the powder [ 27 ]. The overheating, as visible in the MPM data, influences the microstructure formation, which was demonstrated for a Ti-6Al-4V impeller [ 48 ]. A manual analysis of melt pool fluctuations provided an inverse relationship between the plastic elongation of Ti-6Al-4V and the total volume of 3D “melt pool events” [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

et al. 2020

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The potential of in situ melt pool monitoring (MPM) for parameter development and furthering the process understanding in Laser Powder Bed Fusion (LPBF) of CuCr1Zr was investigated. Commercial MPM systems are currently being developed as a quality monitoring tool with the aim of detecting faulty parts already in the build process and, thus, reducing costs in LPBF. A detailed analysis of coupon specimens allowed two processing windows to be established for a suitably dense material at layer thicknesses of 30 µm and 50 µm, which were subsequently evaluated with two complex thermomechanical-fatigue (TMF) panels. Variations due to the location on the build platform were taken into account for the parameter development. Importantly, integrally averaged MPM intensities showed no direct correlation with total porosities, while the robustness of the melting process, impacted strongly by balling, affected the scattering of the MPM response and can thus be assessed. However, the MPM results, similar to material properties such as porosity, cannot be directly transferred from coupon specimens to components due to the influence of the local part geometry and heat transport on the build platform. Different MPM intensity ranges are obtained on cuboids and TMF panels despite similar LPBF parameters. Nonetheless, besides identifying LPBF parameter windows with a stable process, MPM allowed the successful detection of individual defects on the surface and in the bulk of the large demonstrators and appears to be a suitable tool for quality monitoring during fabrication and non-destructive evaluation of the LPBF process.

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Section: Introductionmentioning

confidence: 99%

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

et al. 2020

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“…With a support below, a part can enhance the temperature uniformity during the building process due to heat transfer and also reduce the warping deformation of the forming part by maintaining the stress balance [ 19 ]. The use of a support is also beneficial for improving the density and mechanical properties of building parts [ 20 , 21 ]. The effects of power and scanning speed on the relative density and strength of samples with or without support are shown in Figure 4 .…”

Section: Resultsmentioning

confidence: 99%

Densification, Microstructure, and Mechanical Properties of Additively Manufactured 2124 Al–Cu Alloy by Selective Laser Melting

et al. 2020

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Owing to its high specific strength and low density, Al–Cu alloys have been extensively used in aerospace for lightweight components. Additive manufacturing techniques such as selective laser melting, which offers geometric freedom, is suitable for topology-optimized designs. In this study, the effect of processing parameters on the densification, microstructure, and mechanical properties of additively manufactured Al–Cu alloy 2124 by selective laser melting was investigated. Parameters such as laser power, scanning speed, hatch spacing, and use of a support were studied. The results revealed that a grille support with a hollow structure played a resistant role in the transfer of heat to the base plate, thus reducing the temperature gradient and lessening cracks in the building part. Smaller hatch spacing was beneficial for the achievement of a higher relative density and strength due to track re-melting and liquid phase backflow, which could fill cracks and pores during the building process. An ultimate tensile strength as high as 300 MPa of the vertically built sample was obtained at optimized processing parameters, while the elongation was relatively limited. Moreover, columnar grains were found to be responsible for the anisotropy of the mechanical properties of the as-printed 2124 alloy.

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“…[14,16,26,27] The decomposition of a¢ martensite during the cooling stage of the SLM process was not observed in this study. [3,10] According to the quantitative results obtained from the image analysis software, the average sizes of the columnar grains in the SLM sample along the Y axis and Z axis were, respectively, 55 and 398 lm. Although the width of the columnar grains in the SLM sample was close to that in the SLM solid Ti-6Al-4V alloy, the length of the former was obviously shorter than that of the latter.…”

Section: Resultsmentioning

confidence: 99%

“…ADDITIVE manufacturing (AM) is a versatile method for fabricating materials with complex three-dimensional geometry and designed pore characteristics. [1][2][3] Both nearly fully-dense materials and high-porosity cellular materials can be built by AM layer-by-layer. Powder bed fusion (PBF) with a laser beam or electron beam as the heating source is the dominant technique for AM metallic materials.…”

Section: Introductionmentioning

confidence: 99%

Compression Property, Deformation Behavior, and Fracture Mechanism of Additive-Manufactured Ti-6Al-4V Cellular Solid with a New Cuboctahedron Structure

Chen

Chiang

et al. 2020

Metall Mater Trans A

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Laser powder bed fusion is a major additive manufacturing process for manufacturing cellular metallic materials. The main objective of this study was to clarify the influences of microstructure on the compressive deformation behavior and fracture mechanism of selective laser melted (SLM) cellular Ti-6Al-4V alloy with a new cuboctahedron structure using in-situ observation in combination with the digital image correlation technique. The results indicated that the compressive stress-strain curve of the SLM specimen was serrated in the plateau regime due to the brittle struts with a¢-martensite. Nevertheless, hot isostatic pressing (HIP) at 1000°C/ 150 MPa transformed the microstructure from brittle a¢-martensite to ductile a + b dual phases. In the HIP specimen, the struts plastically collapsed layer-by-layer with increasing compressive strain and were then extruded into the surrounding pores, resulting in a smooth stress-strain curve. Furthermore, the HIP treatment also improved the energy absorption at 50 pct strain from 68.1 to 77.4 MJ/m 3 and maintained the uniformity in the width of the cellular material. These effects are advantageous to energy absorbing applications and alleviating the risk of biomedical implants.

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Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting

Cited by 40 publications

References 10 publications

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

Densification, Microstructure, and Mechanical Properties of Additively Manufactured 2124 Al–Cu Alloy by Selective Laser Melting

Compression Property, Deformation Behavior, and Fracture Mechanism of Additive-Manufactured Ti-6Al-4V Cellular Solid with a New Cuboctahedron Structure

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