A processing diagram for high-density Ti-6Al-4V by selective laser melting
ISSN: 1355-2546
Article publication date: 23 October 2018
Issue publication date: 21 November 2018
Abstract
Purpose
Density optimization is the first critical step in building additively manufactured parts with high-quality and good mechanical properties. The authors developed an approach that combines simulations and experiments to identify processing parameters for high-density Ti-6Al-4V using the laser powder-bed-fusion technique. A processing diagram based on the normalized energy density concept is constructed, illustrating an optimized processing window for high- or low-density samples. Excellent mechanical properties are obtained for Ti-6Al-4V samples built from the optimized window.
Design/methodology/approach
The authors use simple, but approximate, simulations and selective experiments to design parameters for a limited set of single track experiments. The resulting melt-pool characteristics are then used to identify processing parameters for high-density pillars. A processing diagram is built and excellent mechanical properties are achieved in samples built from this window.
Findings
The authors find that the laser linear input energy has a much stronger effect on the melt-pool depth than the melt-pool width. A processing diagram based on normalized energy density and normalized hatch spacing was constructed, qualitatively indicating that high-density samples are produced in a region when 1 < E* < 2. The onset of void formation and low-density samples occur as E* moves beyond a value of 2. The as-built SLM Ti-6Al-4V shows excellent mechanical performance.
Originality/value
A combined approach of computer simulations and selected experiments is applied to optimize the density of Ti-6Al-4V, via laser powder-bed-fusion (L-PBF) technique. A series of high-density samples are achieved. Some special issues are identified for L-PBF processes of Ti-6Al-4V, including the powder particle sticking and part swelling issues. A processing diagram is constructed for Ti-6Al-4V, based on the normalized energy density and normalized hatch spacing concept. The diagram illustrates windows with high- and low-density samples. Good mechanical properties are achieved during tensile tests of near fully dense Ti-6Al-4V samples. These good properties are attributed to the success of density optimization processes.
Keywords
Acknowledgements
The authors thank Wayne King for generating the results of the Eagar-Tsai simulations and Cheng Saw for performing XRD measurements. The experimental setup for the single tracks was put together by Paul Alexander. Both the single track and pillars were built at Fineline (NC, USA). The authors also thank Steve Burke for coordinating the builds. The processing of the single-track plate and density pillars was completed by Cheryl Evans, Edwin Sedillo, Sharon Torres and David Urabe. Inspiring discussion with Saad Khairallah is acknowledged. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Citation
Wang, Y.(M)., Kamath, C., Voisin, T. and Li, Z. (2018), "A processing diagram for high-density Ti-6Al-4V by selective laser melting", Rapid Prototyping Journal, Vol. 24 No. 9, pp. 1469-1478. https://doi.org/10.1108/RPJ-11-2017-0228
Publisher
:Emerald Publishing Limited
Copyright © 2018, Emerald Publishing Limited