Perhaps your Columnar-to-Equiaxed Transition isn't what you think it is? [VIDEO ABSTRACT]

Achieving refined β-grain structures in additively manufactured (AM) titanium alloys can be difficult. Why is this? What if something unexpected is going on? We investigated one particularly...odd mechanism in Ti-6Al-4V built with wire-arc additive manufacturing. This video also covers the solidification theory background for the topic. Original research paper: https://doi.org/10.1007/s11661-024-07... Research credits: A. E. Davis, J. Wainwright, V. K. Sahu, D. Dreelan, X. Chen, J. Ding, T. Flint, S. Williams, P. B. Prangnell. Video credits: Written by Alec E. Davis. Recorded, produced, and performed by Alec E. Davis. Alec E. Davis is grateful to Jacob R. Kennedy for feedback. This work was supported by grants: NEWAM (EPSRC EP/R027218/1), and Henry Royce Institute for Advanced Materials (EPSRC EP/R00661X/1, EP/S019367/1, EP/P025021/1, and EP/P025498/1). Alec E. Davis is also appreciated for equipment loan from the @materialsavclub. Alec E. Davis links: alec.davis@manchester.ac.uk   / alec_e_davis   https://x.com/alecdavis1986 https://www.threads.net/@alec_e_davis https://www.materials.manchester.ac.uk/ https://www.royce.ac.uk/ Contents: Intro 00:00 Columnar grains & CET in Ti alloys 00:41 Solidification theory Solute partitioning 01:58 Nucleation 04:53 Achieving a CET 07:57 Columnar β grains in Ti AM 10:20 Refining β grains in Ti AM 11:38 Is a CET possible in Ti-6Al-4V high-deposition-rate AM 15:37 Increasing the feedstock rate for a CET in AM 19:45 Original research Increasing the wire feed speed in wire-arc AM 20:50 Twins?! 23:30 Melt-pool reshaping, thermal gradients & solidification rates 24:15 More twins! 25:31 Changing the maximum thermal gradient vector 28:34 Putting everything together in a schematic 32:09 Horizonal columnar grains?! 33:24 Summary 34:14