The anisotropy of laser melting deposition additive manufacturing Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy

Zhu, Yanyan; Tian, Xiangjun; Li, Jia; Wang, Huaming

doi:10.1016/j.matdes.2014.11.001

Cited by 151 publications

(36 citation statements)

References 20 publications

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“…However, the most significant property anisotropy was noticed in the ductility data, which was much worse when measured in the horizontal direction. Zhu et al [14] in their review about laser metal deposition (LMD) of Ti alloy point out that for some authors, the as-deposited samples exhibited higher strength and lower ductility at the longitudinal direction compared to the transverse direction, although they found themselves and from other publications diverging results. As property anisotropy is undesirable, layer building strategies on the mechanical properties of printed part have been the main focus of several works.…”

Section: Introductionmentioning

confidence: 99%

Exploring the use of switchback for mitigating homoepitaxial unidirectional grain growth and porosity in WAAM of aluminium alloys

Yehorov

Silva

Scotti

2019

Int J Adv Manuf Technol

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In this work, an alternative approach to prevent unidirectional grain growth in wire + arc additive manufacturing (WAAM) is proposed and assessed, by moving cyclically the torch forward and backward, likewise the welding technique known as switchback. A series of tests were planned with CMT (cold metal transfer) process to compare three wall-like build-ups, which uses different deposition patterns, namely, in one-way direction, reverse direction, and switchback. The same equivalent travel speed and number of deposited layers were kept among them. Longitudinal sections were taken to identify the grain growth behaviour. Finally, samples were removed from the walls for porosity evaluation. The results confirmed the characteristics of unidirectional grain growth, when one-way direction condition was employed, and the break of growth direction between layers, when reverse direction was used, yet a zigzag pattern became present. Differently, the application of switchback showed no preferential or unidirectional grain growth, suggesting less anisotropy of mechanical properties. In addition, switchback reduced porosity.

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Section: Introductionmentioning

confidence: 99%

Exploring the use of switchback for mitigating homoepitaxial unidirectional grain growth and porosity in WAAM of aluminium alloys

Yehorov

Silva

Scotti

2019

Int J Adv Manuf Technol

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“…Extensive study has been performed on these alloys in terms of structural integrity (e.g. porosity) [3][4][5], geometric integrity [3], microstructure [3][4][5][6][7][8][9][10][11][12][13][14], residual stress [15], distortion [3,15], mechanical properties and anisotropy [3,5,10,12] and the influence of laser processing condition and post-build heat treatment and hot isostatic pressing [3,5,16]. Throughout these studies, it is well understood that these alloys are liable to development of porosity especially lack-of-fusion pores at the inter-layer boundaries during DLD which are blamed for tensile anisotropy [3,5].…”

Section: Introductionmentioning

confidence: 99%

Microstructural control during direct laser deposition of a β-titanium alloy

2015

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a b s t r a c tA concern associated with Direct Laser Deposition (DLD) is the difficulty in controlling microstructure due to rapid cooling rates after deposition, particularly in beta-Ti alloys. In these alloys, the beta-phase is likely to exist following DLD, instead of the desirable duplex alpha + beta microstructure that gives a good balance of properties. Thus, in this work, a parametric study was performed to assess the role of DLD parameters on porosity, build geometry, and microstructure in a beta-Ti alloy, Ti-5Al-5Mo-5V-3 Cr (Ti5553). The builds were examined using optical microscopy, scanning electron microscopy, and X-ray diffraction. Microhardness measurements were performed to assess the degree of re-precipitation of alpha-phase following an in situ dwelling and laser annealing procedure. The study identified several processing conditions that enable deposition of samples with the desired geometry and low porosity level. The microstructure was dominated by beta-phase, except for the region near the substrate where a limited amount of alpha-precipitates was present due to reheating effect. Although the microstructure was a mixture of equiaxed and columnar beta-grains alongside infrequent fine alpha-precipitates, the builds showed fairly uniform microhardness in different regions. In situ dwelling and annealing did not cause an obvious change in porosity, but did promote the formation of alpha-precipitates.

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“…In spite of their unique assets, additive manufacturing technologies also suffer from major drawbacks when compared to traditional construction methodologies: at first, they are not scalable, contrary to, for instance, casting techniques where the mold, once it is constructed, can serve to produce quickly and efficiently thousands of copies of the desired component. What's more, because of the specific path followed by the printing nozzle or laser, the material properties of parts produced by additive manufacturing methods are not precisely controlled, and many ongoing studies aim at quantifying the induced anisotropic behavior; see for instance [1,46].…”

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confidence: 99%

Structural optimization under overhang constraints imposed by additive manufacturing technologies

Allaire

Dapogny

Estevez

et al. 2017

Journal of Computational Physics

170

103

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This article addresses one of the major constraints imposed by additive manufacturing processes on shape optimization problems -that of overhangs, i.e. large regions hanging over void without sufficient support from the lower structure. After revisiting the 'classical' geometric criteria used in the literature, based on the angle between the structural boundary and the build direction, we propose a new mechanical constraint functional, which mimics the layer by layer construction process featured by additive manufacturing technologies, and thereby appeals to the physical origin of the difficulties caused by overhangs. This constraint, as well as some variants, are precisely defined; their shape derivatives are computed in the sense of Hadamard's method and numerical strategies are extensively discussed, in two and three space dimensions, to efficiently deal with the appearance of overhang features in the course of shape optimization processes.

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The anisotropy of laser melting deposition additive manufacturing Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy

Cited by 151 publications

References 20 publications

Exploring the use of switchback for mitigating homoepitaxial unidirectional grain growth and porosity in WAAM of aluminium alloys

Exploring the use of switchback for mitigating homoepitaxial unidirectional grain growth and porosity in WAAM of aluminium alloys

Microstructural control during direct laser deposition of a β-titanium alloy

Structural optimization under overhang constraints imposed by additive manufacturing technologies

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