Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V

Rakesh R. Kamath; Peeyush Nandwana; Yang Ren; Hahn Choo

doi:10.1016/j.addma.2021.102136

Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V

Rakesh R. Kamath, Peeyush Nandwana, Yang Ren, Hahn Choo

Materials for Advanced Manufacturing

Research output: Contribution to journal › Article › peer-review

10 Scopus citations

Abstract

The effect of a spot melt strategy on the solidification texture, variant selection, phase fraction, and their variations along the build height was investigated in comparison to a conventional linear melt strategy. Ti-6Al-4V alloy samples were manufactured by an electron-beam powder bed fusion process using two different melt strategies and characterized using high-energy synchrotron x-ray diffraction. The linear and spot melt cases resulted in β<100> cube and fiber textures, respectively, with the cube/fiber axis nearly parallel to the build direction. The α phase exhibited Burgers orientation relationship (BOR) with the parent β phase for both melt strategies. Although all of the key texture components and the BOR between the α and β phases were consistently observed in both cases along the build height, there were several measurable differences between the two. At the top of the build height, the β<100> build texture intensity was stronger in the linear case. However, the texture intensity in the linear case decreased gradually from the top to near the substrate, whereas the spot melt case did not show this trend. Moreover, the BOR was examined along the build height and the results showed that there is a distinct variant selection in the spot melt case, unlike the linear case. Specifically, the planar variants sharing (1̅01)_β|| (0002)_α with [2̅2̅2̅]_β and [22̅2]_β were the most prominent in the spot melt, but no preference was identified in the directional variants. The β phase fraction was slightly lower in the spot melt case compared to the linear case. In both the cases, the β phase fraction decreased moving towards the substrate but remained significantly higher than that of the powder feedstock. Overall, the novel spot melt strategy produced a more homogeneous microstructure in terms of both the phase fraction and texture across the build height.

Original language	English
Article number	102136
Journal	Additive Manufacturing
Volume	46
DOIs	https://doi.org/10.1016/j.addma.2021.102136
State	Published - Oct 2021

Funding

This research was sponsored by the Department of the Navy, Office of Naval Research under ONR award number N00014-18-1-2794. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Office of Naval Research. The research was also sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office under contract DEAC05-00OR22725 with UT-Battelle, LLC. Access to the Oak Ridge National Laboratory's (ORNL) AM equipment at ORNL's Manufacturing Demonstration Facility (MDF) was facilitated by US Department of Energy's Strategic Partnership Projects (SPP) mechanism. More information can be found at https://science.energy.gov/lp/strategicpartnership-projects. Research sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Industrial Technologies Program, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. R. R. Kamath and H. Choo are grateful for helpful comments from Prof. S. S. Babu (UTK/ORNL) and Ms. Sabina Kumar (UTK). This work is a part of the Ph.D. dissertation study of R. R. Kamath under the supervision of Prof. H. Choo at the University of Tennessee Knoxville.

Funders	Funder number
Office of Energy Efficiency and Renewable Energy, Industrial Technologies Program	DE-AC05-00OR22725
Office of Naval Research	N00014-18-1-2794
U.S. Department of Energy
Advanced Manufacturing Office	DEAC05-00OR22725
Office of Science
Office of Energy Efficiency and Renewable Energy
Argonne National Laboratory	DE-AC02-06CH11357
Oak Ridge National Laboratory
U.S. Navy
University of Tennessee, Knoxville

Keywords

Additive manufacturing
Crystallographic texture
Electron beam powder bed fusion
Melt strategy
Ti-6Al-4V

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.addma.2021.102136

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title = "Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V",

abstract = "The effect of a spot melt strategy on the solidification texture, variant selection, phase fraction, and their variations along the build height was investigated in comparison to a conventional linear melt strategy. Ti-6Al-4V alloy samples were manufactured by an electron-beam powder bed fusion process using two different melt strategies and characterized using high-energy synchrotron x-ray diffraction. The linear and spot melt cases resulted in β<100> cube and fiber textures, respectively, with the cube/fiber axis nearly parallel to the build direction. The α phase exhibited Burgers orientation relationship (BOR) with the parent β phase for both melt strategies. Although all of the key texture components and the BOR between the α and β phases were consistently observed in both cases along the build height, there were several measurable differences between the two. At the top of the build height, the β<100> build texture intensity was stronger in the linear case. However, the texture intensity in the linear case decreased gradually from the top to near the substrate, whereas the spot melt case did not show this trend. Moreover, the BOR was examined along the build height and the results showed that there is a distinct variant selection in the spot melt case, unlike the linear case. Specifically, the planar variants sharing (1̅01)β|| (0002)α with [2̅2̅2̅]β and [22̅2]β were the most prominent in the spot melt, but no preference was identified in the directional variants. The β phase fraction was slightly lower in the spot melt case compared to the linear case. In both the cases, the β phase fraction decreased moving towards the substrate but remained significantly higher than that of the powder feedstock. Overall, the novel spot melt strategy produced a more homogeneous microstructure in terms of both the phase fraction and texture across the build height.",

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author = "Kamath, {Rakesh R.} and Peeyush Nandwana and Yang Ren and Hahn Choo",

note = "Publisher Copyright: {\textcopyright} 2021 Elsevier B.V.",

year = "2021",

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Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V

Abstract

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Keywords

UN SDGs

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