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Clarifying the formation of equiaxed grains and microstructural refinement in the additive manufacturing of Ti-Cu

Authors :
Alec I. Saville
Adriana Eres-Castellanos
Andrew B. Kustas
Levi Van Bastian
Donald F. Susan
Dale E. Cillessen
Sven C. Vogel
Natalie A. Compton
Kester D. Clarke
Alain Karma
Amy J. Clarke
Source :
Materials & Design, Vol 248, Iss , Pp 113440- (2024)
Publication Year :
2024
Publisher :
Elsevier, 2024.

Abstract

Controlling microstructural evolution in metallic additive manufacturing (AM) is difficult, especially in producing refined as-built grains instead of coarse, directional grains. Traditional solutions involve adding inoculants to AM feedstocks, but titanium (Ti) alloys cannot employ this approach without producing detrimental secondary phases. Ti-Cu (Ti-copper) alloys offer a solution through constitutional supercooling and/or solid state thermal cycling under AM conditions. This work analyzes a compositionally graded directed energy deposition (DED) Ti-Cu build, single-melt laser tracks, and dilatometric heat treatments to evaluate if, when, and by what mechanism(s) microstructural refinement occurs. Refinement by inoculation of unmelted powder particles was also considered. Constitutional supercooling produced no net microstructural refinement as any equiaxed dendrites which form are remelted with new deposition. This finding agreed with solidification modeling of powder bed fusion-laser beam (PBF-LB) and DED builds. Solid state thermal cycling refined microstructures only during ex-situ dilatometric heat treatments, suggesting build parameter optimization is needed to achieve refinement in-situ. Accidental heterogeneous nucleation on unmelted Ti powder, originating from the different thermophysical properties of Ti and Cu, provided the most significant microstructural refinement. This work systematically assesses the microstructural refinement mechanisms of Ti-Cu in AM builds and offers insights into microstructural control in eutectoid alloys.

Details

Language :
English
ISSN :
02641275
Volume :
248
Issue :
113440-
Database :
Directory of Open Access Journals
Journal :
Materials & Design
Publication Type :
Academic Journal
Accession number :
edsdoj.9bfbbad9fe7e428fae619797f39f2abc
Document Type :
article
Full Text :
https://doi.org/10.1016/j.matdes.2024.113440