Effect of trace lanthanum hexaboride and boron additions on microstructure, tensile properties and anisotropy of Ti-6Al-4V produced by additive manufacturing

Bermingham, Michael; McDonald, Stuart D.; Dargusch, Matthew S.

doi:10.1016/j.msea.2018.02.012

Cited by 125 publications

(41 citation statements)

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“…The error bars represent one standard deviation of three tests. b Change in yield stress of AM-fabricated Ti-6Al-4V by chemical addition 51,52 compared to ultrasound in this work. See Supplementary Table 3 for data and references.…”

Section: Discussionmentioning

confidence: 84%

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Grain structure control during metal 3D printing by high-intensity ultrasound

et al. 2020

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Additive manufacturing (AM) of metals, also known as metal 3D printing, typically leads to the formation of columnar grain structures along the build direction in most as-built metals and alloys. These long columnar grains can cause property anisotropy, which is usually detrimental to component qualification or targeted applications. Here, without changing alloy chemistry, we demonstrate an AM solidification-control solution to printing metallic alloys with an equiaxed grain structure and improved mechanical properties. Using the titanium alloy Ti-6Al-4V as a model alloy, we employ high-intensity ultrasound to achieve full transition from columnar grains to fine (~100 µm) equiaxed grains in AM Ti-6Al-4V samples by laser powder deposition. This results in a 12% improvement in both the yield stress and tensile strength compared with the conventional AM columnar Ti-6Al-4V. We further demonstrate the generality of our technique by achieving similar grain structure control results in the nickel-based superalloy Inconel 625, and expect that this method may be applicable to other metallic materials that exhibit columnar grain structures during AM.

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Section: Discussionmentioning

confidence: 84%

“…Deploying ultrasound, without modifying alloy composition, results in a greater increase in yield stress than alloying with B 51 , LaB 6 (ref. 51 ) and C 52 .…”

Section: Resultsmentioning

confidence: 99%

Grain structure control during metal 3D printing by high-intensity ultrasound

et al. 2020

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“…Tensile bars were machined using modified geometries of ASTM E8M (flat dogbone, 1.5mm x 5mm gauge cross-section x 16mm gauge length) and tested at a crosshead speed of 0.5mm/min. It is well known that Ti-6Al-4V components produced by additive manufacturing can be highly anisotropic and as such, the orientation selected for testing was in the horizontal direction, which is frequently reported to be the least ductile direction in Ti-6Al-4V components manufactured by WAAM in studies previously conducted by Bermingham et al (2018). Five tensile specimens were tested for each condition in this direction to assess the worst case scenario as any oxygen contamination is expected…”

Section: A C C E P T E Dmentioning

confidence: 99%

Sensitivity of Ti-6Al-4V components to oxidation during out of chamber Wire + Arc Additive Manufacturing

Bermingham

Thomson-Larkins

John

et al. 2018

Journal of Materials Processing Technology

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Reactive metals including titanium readily oxidise and should be protected from the atmosphere during Additive Manufacturing processes. This work explores the sensitivity of Ti-6Al-4V components to oxidation contamination during out of chamber Wire + Arc Additive Manufacturing when using inert gas trailing shields. Five Ti-6Al-4V components were produced with varying argon trailing shield configurations that range from ideal inert gas shielding (resulting in no surface contamination) through to very poor inert gas shielding that results in substantial surface oxidation. Despite significant changes in the degree of surface oxide contamination between each component, the overall increase in oxygen concentration in the bulk alloys was minimal and had negligible influence on the tensile strength and ductility.

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“…al. however, has found that the growth restriction actor is a useful tool in determining potential grain refining solutes for both pure titanium and its alloys [32,[49][50][51][52][53][54]. The research found that the growth restriction factor was also applicable for non-binary systems and shows its potential for use in this thesis.…”

Section: The Growth Restriction Factormentioning

confidence: 85%

“…The authors then expanded on this work by applying some of these grain refining solutes to WAAM titanium components. Trace additions of solutes such as boron and lanthanum hexaboride have been shown to refine the microstructures of Ti-6Al-4V components built using WAAM[50,67]. The addition of boron was found to homogenise α phase microstructure by eliminating grain boundary and colony α.While boron was able to reduce the widths of prior-β grains, their columnar structure remained unchanged.…”

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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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Effect of trace lanthanum hexaboride and boron additions on microstructure, tensile properties and anisotropy of Ti-6Al-4V produced by additive manufacturing

Cited by 125 publications

References 50 publications

Grain structure control during metal 3D printing by high-intensity ultrasound

Grain structure control during metal 3D printing by high-intensity ultrasound

Sensitivity of Ti-6Al-4V components to oxidation during out of chamber Wire + Arc Additive Manufacturing

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

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Effect of trace lanthanum hexaboride and boron additions on microstructure, tensile properties and anisotropy of Ti-6Al-4V produced by additive manufacturing

Cited by 125 publications

References 50 publications

Grain structure control during metal 3D printing by high-intensity ultrasound

Grain structure control during metal 3D printing by high-intensity ultrasound

Sensitivity of Ti-6Al-4V components to oxidation during out of chamber Wire + Arc Additive Manufacturing

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

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Sensitivity of Ti-6Al-4V components to oxidation during out of chamber Wire + Arc Additive Manufacturing