Promoting the columnar to equiaxed transition and grain refinement of titanium alloys during additive manufacturing
By M. Bermingham, D. StJohn, J. Krynen, S. Tedman-Jones, Mathew S. Dargusch. Acta Materialia, 2019
654 citations recorded by the source corpus.
Abstract Preventing columnar grain formation during additive manufacturing has become a significant challenge. Columnar grains are generally regarded as unfavourable as their presence can impart solidification defects and mechanical property anisotropy, however, the thermal conditions experienced during additive manufacturing make columnar grains difficult to avoid. In this work the thermal conditions during solidification (cooling rate, temperature gradients) are characterised during wire based additive manufacturing. For the selection of deposition conditions that favour equiaxed grain formation, the role of alloy constitution is explored in three classical alloy design regimes: an alloy containing no grain refiners (Ti 6Al 4V); an alloy only containing grain refining solutes (Ti 3Al 8V 6Cr 4Mo 4Zr); and an alloy containing both grain refining solute and nucleant particles (Ti 3Al 8V 6Cr 4Mo 4Zr + La2O3). Substantial refinement and equiaxed grain formation is achieved in the latter case which is attributed to β-Ti nucleation on La2O3. However, the thermal environment is dynamic during additive manufacturing and equiaxed grain formation is only achievable when temperature gradients decrease sufficiently to permit constitutional supercooling.
Subfields: Aerospace Engineering, Materials Chemistry, Mechanical Engineering
View Paper: https://www.semanticscholar.org/paper/e204cb7de6f5556326cf5af72015b4c432592983
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Citations in the corpus
- Towards understanding grain nucleation under Additive Manufacturing solidification conditions (2020, methodology): “Experimental verification of CET in AM processes include the results from Bermingham et al [41] who reported a mix of columnar and equiaxed grains in Ti-alloys with La2O3 particles produced by a wire based AM process.”
- The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review (2021, background): “The directional grain growth that occurs in titanium alloys in additive manufacturing can be reduced by an intermediate forming process [39,47,98,107,299,305,312,313], the addition of further elements like boron, silicon or other elements [303,311,317,321,322] or applying post-weld heat treatment [3”
- Grain refinement of stainless steel in ultrasound-assisted additive manufacturing (2020, methodology): “conditions, including ultrasonic [17, 35, 36] and AM [37-39] conditions.”
- Revisiting fundamental welding concepts to improve additive manufacturing: From theory to practice (2020, methodology): “Ti-6Al-4V Cr-Mo-Zr Grain refinement; Columnar to equiaxed transition [252]”