The influence of nanoparticles on dendritic grain growth in Mg alloys

Guo, Enyu; Shuai, Sansan; Kazantsev, Daniil; Karagadde, Shyamprasad; Phillion, A.B.; Jing, Tao; Li, Wenzhen; Lee, Peter

doi:10.1016/j.actamat.2018.04.023

Cited by 91 publications

(25 citation statements)

References 58 publications

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“…Firstly, this generates a centripetal Marangoni convection which drives any pre-existing pores to the bottom of the melt pool; secondly, the Marangoni convection deepens the melt pool and facilitates pore coalescence. Our results suggest the oxide stabilises the pores once formed, reduces the interfacial energy, and hence increases the pore size[71,72]. Given that the quantification algorithm does not take open pores into account, the sudden decrease of porosity in the second layer build (see event 1 in Pore-B2.2) indicates the formation of an open pore via pore bursting.…”

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confidence: 86%

The effect of powder oxidation on defect formation in laser additive manufacturing

et al. 2019

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Understanding defect formation during laser additive manufacturing (LAM) of virgin, stored, and reused powders is crucial for the production of high quality additively manufactured parts. We investigate the effects of powder oxidation on the molten pool dynamics and defect formation during LAM. We compare virgin and oxidised Invar 36 powder under overhang and layer-by-layer build conditions using in situ and operando X-ray Imaging. The oxygen content of the oxidised powder was found to be ca. 6 times greater (0.343 wt.%) than the virgin powder (0.057 wt.%). During LAM, the powder oxide is entrained into the molten pool, altering the Marangoni convection from an inward centrifugal to an outward centripetal flow. We hypothesise that the oxide promotes pore nucleation, stabilisation, and growth. We observe that spatter occurs more frequently under overhang conditions compared to layer-by-layer conditions. Droplet spatter can be formed by indirect laser-driven gas expansion and by the laser-induced metal vapour at the melt surface. In layer-by-layer build conditions, laser re-melting reduces the pore size distribution and number density either by promoting gas release from keyholing or by inducing liquid flow, partially or completely filling pre-existing pores. We also observe that pores residing at the track surface can burst during laser re-melting, resulting in either 2 formation of droplet spatter and an open pore or healing of the pore via Marangoni flow. This study confirms that excessive oxygen in the powder feedstock may cause defect formation in LAM.

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confidence: 86%

The effect of powder oxidation on defect formation in laser additive manufacturing

et al. 2019

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“…Their observations revealed that the growth behavior of metal dendrites is remarkably different from that of transparent organic analogs, in terms of local curvatures, solid volumes, and interfacial areas [75]. Lee and coworkers [76] have extended our understanding of these phenomena by probing dendritic solidification in nanoparticle (NP)-reinforced alloys via μXRT. Data were reconstructed through MBIR [62], which offered substantial improvement in signal-to-noise over FBP (compare Figures 3(a-b)).…”

Section: X-ray Absorption-contrast Microtomographymentioning

confidence: 99%

Characterization of metals in four dimensions

Shahani

Xiao

Lauridsen

et al. 2020

Materials Research Letters

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The ability to watch the three-dimensional (3D) evolution of structural materials is a breakthrough in non-destructive characterization. In particular, X-ray tomographic imaging techniques have found success in revealing the underlying mechanisms of microstructural transformations in partially and fully solidified metals. Here we review the most important developments in four-dimensional X-ray microscopy, focusing on absorption-and diffraction-based techniques in the laboratory and the synchrotron. In light of recent progress in this area, we identify critical issues that point to directions for future research in imaging the evolution of heterogeneous microstructures at extreme space and time scales. IMPACT STATEMENT Four-dimensional X-ray tomography has opened a new paradigm in physical metallurgy, allowing us to characterize the various epochs of microstructural evolution in 3D and as a function of time.

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“…In a recent study, we investigated the influence of SiC nano-sized particles (NP) on the nucleation and growth of dendrites in a set of Mg-Zn-Al alloys using in-situ synchrotron X-ray tomography [17]. In this study, those results are extended and compared to experiments performed on Al-Cu alloys with and without nano/micron-sized particles (MP).…”

Section: Introductionmentioning

confidence: 99%

In Situ Tomographic Observation of Dendritic Growth in Mg/Al Matrix Composites

et al. 2019

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Understanding the interaction of nano/micro-particles with evolving microstructures during solidification is critical for developing new materials with improved mechanical properties through either particulate reinforcement and/or via microstructural refinement. In this study, we investigate the influence of nanoparticles on the evolving dendrites in both Mg and Al based metal matrix composites via in situ synchrotron tomography. Ultrasonic treatment was applied during the raw material preparation to break the particle agglomeration. The solidification of primary dendrites was characterized and quantified. The results reveal the underlying physical mechanisms that enable nanoparticles to modify the grain size in both alloy systems. These insights into dendrite evolution help both to inform and validate numerical models of the solidification microstructures of metal matrix composites.

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The influence of nanoparticles on dendritic grain growth in Mg alloys

Cited by 91 publications

References 58 publications

The effect of powder oxidation on defect formation in laser additive manufacturing

The effect of powder oxidation on defect formation in laser additive manufacturing

Characterization of metals in four dimensions

In Situ Tomographic Observation of Dendritic Growth in Mg/Al Matrix Composites

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