The Challenges Associated with the Formation of Equiaxed Grains during Additive Manufacturing of Titanium Alloys

John, D. H. St; McDonald, Stuart D.; Bermingham, Michael; Mereddy, S.; Prasad, Arvind; Dargusch, Matthew S.

doi:10.4028/www.scientific.net/kem.770.155

Cited by 31 publications

(11 citation statements)

References 15 publications

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“…[21][22][23][24] However, there are limited reports of incorporating the model with AM solidification conditions. [25,26] In addition, the interaction of multiple thermal cycles during AM makes the solidification process more complex than conventional solidification processing.…”

Section: Metal Fusion Additive Manufacturing (Am) Ismentioning

confidence: 99%

Grain Refinement of Alloys in Fusion-Based Additive Manufacturing Processes

Zhang

Prasad

Bermingham

et al. 2020

Metall Mater Trans A

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159

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Section: Metal Fusion Additive Manufacturing (Am) Ismentioning

confidence: 99%

Grain Refinement of Alloys in Fusion-Based Additive Manufacturing Processes

Zhang

Prasad

Bermingham

et al. 2020

Metall Mater Trans A

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159

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“…Generally, deep dimples are attributed to the decrease of resistance to dislocation sliding. [ 34,35 ] However, the size of dimples became shallower, and the number of secondary cracks increased with boron addition (Figure 10d–f). As reported by Zhang et al, [ 27 ] the excess TiB particles in Ti–6Al–4V manufactured by direct laser deposition embrittled the alloy and reduced the ductility.…”

Section: Resultsmentioning

confidence: 99%

Effects of Trace Boron Addition and Different Arc Types on Microstructure and Mechanical Properties of TC11/TC17 Dual Alloy Fabricated by Wire Arc Additive Manufacturing

et al. 2022

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Wire arc additive manufacturing (WAAM) provides an efficient and low‐cost potential for manufacturing TC11/TC17 dual titanium alloy. In this work, six deposition samples were fabricated for the test of microstructure and mechanical properties by the combination of trace boron addition and different arc types (direct current (DC), high frequency pulsed current (HC), low frequency pulsed current (LC)). Results show that the epitaxial growth β columnar grains were formed except for the combination of low frequency pulsed current and trace boron addition (LCB). A special microstructure of coarser α phases surrounding thin α phases was formed by the effect of LC arc or trace boron addition. Some TiB particles exhibited a specific orientation relationship with surrounding α phases, but not all: (0001)α||(001)TiB and <11‐20>α||[010]TiB. About mechanical properties, the elongation decreased with trace boron addition, and comprehensive mechanical properties of LC method was better than that of DC or HC methods whether it contained trace boron or not, with tensile strength of 1057 MPa and elongation of 14.4% in the longitudinal direction. Meanwhile, the strength of LCB group is highest than that of other groups, which is caused by the refined β grains and the uniform distribution of TiB particles.

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“…The widths of α laths have been observed to influence the yield strengths of additively manufactured Ti-6Al-4V structures in accordance with the Hall-Petch relationship[71]. Since the β phase influences α-colony size and orientation, the lower widths of the prior-β grains in the longitudinal direction may have increased the yield strength in that direction[39].…”

mentioning

confidence: 63%

“…It was identified that, to refine AM samples to the same degree as cast microstructures, a potent nucleant must be identified that can work in conjunction with the solutes. These findings led to a publication by StJohn et al [39] that focused on the challenges of obtaining an equiaxed microstructure during the additive manufacturing of titanium. This publication utilised research conducted as part of this candidature as a foundation to determine conditions that promoted the growth of equiaxed grains during AM.…”

Section: Chapter 6 Outcomes Conclusion and Future Workmentioning

confidence: 99%

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Effect of alloy composition on the microstructure of titanium alloys produced by wire & Arc Additive Manufacturing

Mereddy¹

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Additive Manufacturing (AM) technologies seek to minimise material waste in the manufacturing industry. Such technologies are able to be used with various plastics, metals and composites and can impact a multitude of industries. Users of titanium and its alloys can benefit from additive manufacturing due to the challenges present in the subtractive fabrication of titanium components. While AM is a solution to the issue of high material waste observed in titanium manufacturing, most AM technologies suffer from columnar, anisotropic microstructures that hinder their widespread use. A review of recent literature has highlighted the need for the development of an effective grain refining solution to additively manufactured titanium components. Solute addition was chosen as the method of grain refinement due to its success in cast titanium. Silicon and carbon additions were found to be effective in refining the microstructure of AM titanium components. The addition of up to 0.75wt% silicon to commercially pure titanium manufactured by wire and arc AM resulted in a significant reduction of the prior-β grain size. Additions of up to 0.41wt% carbon were also made to Ti-6Al-4V components built using wire and arc AM. Microstructural analysis revealed that the prior-β grain size and α-lath length reduced by a factor of 5-6. The addition of 0.1wt% carbon proved to be the most effective in increasing yield and tensile strengths, with an improvement of 9% over unalloyed Ti-6Al-4V. For higher levels of carbon, strength and ductility both decreased. The addition of 0.1% carbon also resulted in a 7% increase in maximum compressive strength when compared to unalloyed Ti-6Al-4V. The effectiveness of both solutes showed that grain refiners utilised for cast titanium can also be applied in AM processes. However, while both solutes refined microstructure to a degree, columnar grains remained. It was determined that potent nucleant particles must be added in conjunction with solutes to achieve a homogenous equiaxed microstructure in AM titanium components. This research has also shown that the interdependency theory and the growth restriction factor are both applicable to the wire and arc AM process. These theories can be utilised by future researchers to further investigate the grain refinement of AM titanium. The experimental methodologies developed during the course of this research can also aid future researchers. The findings from this research can be utilised in future research to develop commercially viable grain refiners for not only titanium, but other materials as well. The effectiveness of silicon and carbon can also be tested using other AM technologies to further understand the mechanisms of grain refinement during AM.

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The Challenges Associated with the Formation of Equiaxed Grains during Additive Manufacturing of Titanium Alloys

Cited by 31 publications

References 15 publications

Grain Refinement of Alloys in Fusion-Based Additive Manufacturing Processes

Grain Refinement of Alloys in Fusion-Based Additive Manufacturing Processes

Effects of Trace Boron Addition and Different Arc Types on Microstructure and Mechanical Properties of TC11/TC17 Dual Alloy Fabricated by Wire Arc Additive Manufacturing

Effect of alloy composition on the microstructure of titanium alloys produced by wire & Arc Additive Manufacturing

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