On the observation of annealing twins during simulating β-grain refinement in Ti–6Al–4V high deposition rate AM with in-process deformation

Donoghue, Jack; Davis, Alec; Daniel, Christopher S.; Garner, Alistair; Martina, Filomeno; Fonseca, João Quinta da; Prangnell, P.B.

doi:10.1016/j.actamat.2020.01.009

Cited by 35 publications

(19 citation statements)

References 42 publications

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“…[2,29,30] Why interpass rolling is so effective in refining the grain structure, when applying relatively low applied plastic strains (< 20 pct), is still the subject of on-going research. However, Donoghue et al [31,32] suggested that deformation and rapid re-heating can cause twinning of the b grains when they re-grow, though this is understood to be normally less favorable in Ti64. [33] In addition, when rolling is applied cyclically to each added layer, it is particularly effective because it breaks up the grain structure in each layer and prevents the competitive re-growth through multiple added layers that is required to produce columnar structures.…”

Section: Inter-pass Deformationmentioning

confidence: 99%

“…The mechanisms by which the new b-grain orientations first form within the peened layer have not been investigated here in detail and are the subject of another publication. [32] However, to refine the grain size, new b-grain orientations must be generated as a result of the deformation induced by the surface peening process, and/or when the b phase re-grows during the a fi b transformation. Parallel studies [32] on the origin of the relatively low plastic strain required to obtain high levels of b-grain refinement in WAAM inter-pass rolling have used simulations and rapid heating experiments to investigate the refinement mechanism in more detail.…”

Section: E the Effectiveness Of B-grain Refinement By Surface Peeningmentioning

confidence: 99%

“…[32] However, to refine the grain size, new b-grain orientations must be generated as a result of the deformation induced by the surface peening process, and/or when the b phase re-grows during the a fi b transformation. Parallel studies [32] on the origin of the relatively low plastic strain required to obtain high levels of b-grain refinement in WAAM inter-pass rolling have used simulations and rapid heating experiments to investigate the refinement mechanism in more detail. This work suggests that, under the unusual rapid heating conditions present in the WAAM process, some new grain orientations originate from heterogeneities within the deformed state, such as at prior b-grain boundaries, but other grain orientations can also arise from deformation-induced annealing twinning.…”

Section: E the Effectiveness Of B-grain Refinement By Surface Peeningmentioning

confidence: 99%

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The Effectiveness of Grain Refinement by Machine Hammer Peening in High Deposition Rate Wire-Arc AM Ti-6Al-4V

Hönnige

Davis

et al. 2020

Metall Mater Trans A

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Surface deformation, applied in-process by machine hammer peening (MHP), has the potential to refine the coarse columnar b-grain structures normally found in high deposition rate Wire-Arc Additive Manufacturing (WAAM) processes with Ti alloys like Ti-6Al-4V. Effective refinement, as well as a reduction in texture strength, has been achieved in relatively thick sections and to a depth that is greater than that expected from the surface deformation induced by MHP. By application of MHP to each deposition track, the average b-grain size could be reduced from cm's to less than 0.5 mm. Systematic experiments have been performed to investigate the origin of this interesting effect, which included 'stop-action' trials and separation of the strain and temperature gradients induced by the two process steps. The maximum depth of the plastic deformation from MHP required to generate new b-grain orientations was determined by electron backscatter diffraction local average misorientation analysis to be < 0.5 mm, which was less than the melt pool depth in the WAAM process. Nevertheless, new b-grain orientations were observed to form within the peened layer ahead of the approaching heat source as the peak temperature rose above the b transus, which then grew into the less deformed core of the wall as the temperature rose. This allowed the new grain orientations to penetrate deeper than the melt pool depth and survive to act as substrates for epitaxial growth at the fusion boundary during solidification, resulting in significant grain refinement.

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Section: Inter-pass Deformationmentioning

confidence: 99%

Section: E the Effectiveness Of B-grain Refinement By Surface Peeningmentioning

confidence: 99%

Section: E the Effectiveness Of B-grain Refinement By Surface Peeningmentioning

confidence: 99%

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The Effectiveness of Grain Refinement by Machine Hammer Peening in High Deposition Rate Wire-Arc AM Ti-6Al-4V

Hönnige

Davis

et al. 2020

Metall Mater Trans A

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Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured Mild Steel by Welding with Trailing Hammer Peening

Xiong

Qin

et al. 2021

steel research int.

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The microstructure of the parts manufactured by Wire Arc Additive Manufacture (WAAM) is dominated by columnar grains with large size, [1][2][3][4][5] which seriously affects the service performance and life of the parts. [2,[5][6][7] There are two kinds of viable approaches to improve the microstructure of the welds produced by Additive Manufacturing (AM): adjusting the welding process parameters [8][9][10][11][12][13] and introducing external auxiliary means. [14][15][16][17][18][19][20][21] The formation of "AMþ" hybrid AM technology by introducing external auxiliary means to assist the AM has shown good effect and prospect in solving the problem, especially the introduction of specific kinds of energy field such as the mechanical force-energy field, [14][15][16] the ultrasonic field, [17,18] the laser-energy field, [19] and the electromagnetic field. [20,21] However, the mechanical force-energy field-assisted AM technology has attracted much more attention of researchers in the researching field, for the reason of owning the following advantages: a remarkable effect, simple equipments, lower cost, and strong reproducibility, as well as a great potential in academic research and engineering application. [15,16] The interlayer rolling is the most commonly used WAAM technique assisted by mechanical forceenergy field in current researches. [1,2,[4][5][6]16,[22][23][24][25][26][27][28][29][30] The technique is equipped with heavy equipment to generate continuous rolling static pressure up to thousands of newtons. The large static pressure can drive the roller to introduce continuous and uniform plastic deformation in the additive layers which can improve the microstructure and mechanical properties of the additive layers. [16,30] Many researchers [1,2,5,16,25,26] have used this kind of technique to process different metal additive layers, studied the influence on the microstructure evolution of the additive layers under the process, and finally, revealed the influence mechanism of the microstructure evolution of the additive layers on the mechanical properties under the process.Interlayer hammer peening is another novel WAAM technique proposed in recent years, [15] which need not be assembled with heavy equipment to provide greater continuous static pressure but can combine with industrial robots well, so as to achieve a higher processing freedom. [15,31] This technique provides some new thoughts and directions for exploring and expanding the new style of "AMþ" hybrid AM technology. Different from the interlayer rolling technique, the interlayer hammer peening technique has the following characteristics: 1) the acting force is instantaneous impact force with the very short acting time, and the instantaneous contact force is great with high plastic

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Development of Microstructure and Mechanical Properties of TiAl6V4 Processed by Wire and Arc Additive Manufacturing

et al. 2022

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Wire and arc additive manufacturing (WAAM) has the potential to significantly reduce material waste due to the milling of components made of TiAl6V4 (Ti‐64). To keep up with the market development, this resource‐efficient technology is becoming increasingly important to achieve climate policy goals. Therefore, this study not only focuses on the influence of different process parameters, such as torch and wire feed speed, but also different gas mixtures on the microstructure and related mechanical properties, as well as on the scalability by investigating single‐ to multilayer welded structures. The wire feed speed is found to have a major influence on the geometry and mechanical properties. The use of different process gases, i.e., argon (Ar), helium (He), and a mixture of 70% He and 30% Ar neither significantly affect the microstructure nor the mechanical properties. It is also found that a solution heat treatment followed by an annealing step degrades mechanical properties, while an ordinary stress‐relief heat treatment leads to improved mechanical properties. It is shown that by adapting WAAM process and heat treatment parameters, mechanical properties of additively produced specimens can be achieved, which are fully comparable to milled components.

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On the observation of annealing twins during simulating β-grain refinement in Ti–6Al–4V high deposition rate AM with in-process deformation

Cited by 35 publications

References 42 publications

The Effectiveness of Grain Refinement by Machine Hammer Peening in High Deposition Rate Wire-Arc AM Ti-6Al-4V

The Effectiveness of Grain Refinement by Machine Hammer Peening in High Deposition Rate Wire-Arc AM Ti-6Al-4V

Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured Mild Steel by Welding with Trailing Hammer Peening

Development of Microstructure and Mechanical Properties of TiAl6V4 Processed by Wire and Arc Additive Manufacturing

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