Abstract
It is necessary to better understand the composition–processing–microstructure relationships that exist for materials produced by additive manufacturing. To this end, Laser Engineered Net Shaping (LENS™), a type of additive manufacturing, was used to produce a compositionally graded titanium binary model alloy system (Ti-xW specimen (0 ≤ x ≤ 30 wt pct), so that relationships could be made between composition, processing, and the prior beta grain size. Importantly, the thermophysical properties of the Ti-xW, specifically its supercooling parameter (P) and growth restriction factor (Q), are such that grain refinement is expected and was observed. The systematic, combinatorial study of this binary system provides an opportunity to assess the mechanisms by which grain refinement occurs in Ti-based alloys in general, and for additive manufacturing in particular. The operating mechanisms that govern the relationship between composition and grain size are interpreted using a model originally developed for aluminum and magnesium alloys and subsequently applied for titanium alloys. The prior beta grain factor observed and the interpretations of their correlations indicate that tungsten is a good grain refiner and such models are valid to explain the grain-refinement process. By extension, other binary elements or higher order alloy systems with similar thermophysical properties should exhibit similar grain refinement.
Original language | English |
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Pages (from-to) | 3594-3605 |
Number of pages | 12 |
Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
Volume | 48 |
Issue number | 7 |
DOIs | |
State | Published - Jul 1 2017 |
Externally published | Yes |
Funding
The authors gratefully acknowledge the support of the National Science Foundation (DMREF-1435872, 1606567, 1434462), in which an MGI strategy is adopted. The authors also acknowledge the engagement of industrial partners through the Center for Advanced Non-Ferrous Structural Alloys (CANFSA), an NSF Industry/University Cooperative Research Center (I/UCRC) between the Iowa State University and the Colorado School of Mines. This article is intended to appear as one of two companion articles. This article focuses on the experimental methods associated with additive manufacturing of Ti-xW specimens, and the companion article by Rolchigo et al. is focused on the simulation of solidification associated with additive manufacturing.
Funders | Funder number |
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NSF Industry/University Cooperative Research Center | |
National Science Foundation | DMREF-1435872, 1624748, 1434462, 1606567 |
Colorado School of Mines | |
Iowa State University |