Estimation of Cooling Rates During Close-Coupled Gas Atomization Using Secondary Dendrite Arm Spacing Measurement

Farrell, Leane; Mullis, Andrew M.; Adkins, Nicholas J.E.

doi:10.1007/s11663-013-9856-2

Cited by 87 publications

(55 citation statements)

References 24 publications

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“…The corresponding terminal velocities in the tube range from  2 m s -1 for a 38 µm droplet to  15 m s -1 for an 850 µm droplet. As with most previous such calculations of cooling rates for particles in-flight [21,22], the cooling rate is well approximated by a power law fit, as shown in Figure 2. The cooling rates calculated are lower (typically by around a factor of 3) than those calculated in [21], also for drop-tube cooling.…”

Section: Thermodynamic Modellingsupporting

confidence: 72%

Microstructure evolution and mechanical properties of drop-tube processed, rapidly solidified grey cast iron

Oloyede

Bigg

Mullis

2016

Materials Science and Engineering: A

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The microstructure, phase composition and microhardness of rapidly solidified grey cast iron BS1452 Grade 250 are compared against the conventionally solidified alloy. Powder samples were prepared using containerless processing via the drop-tube technique. The rapidly cooled droplets were collected and sieved into size range from ≥ 850 µm to ≤ 53 µm diameters corresponding to estimated rates of 200 K s -1 to 23,000 K s -1 . Microstructure evaluations were made by optical and scanning electron microscopy, while XRD was used for identification and analysis of evolved phases. The control sample showed extensive graphite flake formation which was absent in virtually all the droplets samples. With decreasing particle size (increasing cooling rate) we observed an increase in the proportion of Fe 3 C present and the retention of -Fe in preference to -Fe, with the proportion of retained austenite increasing with increasing cooling rate. At the highest cooling rates utilised a Martensitic or acicular ferrite structure was observed. Cooling rates of 200 K s -1 resulted in a doubling of the measured microhardness relative to the as-received (slowly cooled) material. Cooling at the highest rates achieved resulted in a further doubling of the measured microhardness.

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Section: Thermodynamic Modellingsupporting

confidence: 72%

Microstructure evolution and mechanical properties of drop-tube processed, rapidly solidified grey cast iron

Oloyede

Bigg

Mullis

2016

Materials Science and Engineering: A

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“…Figure 4a demonstrates the powder particles that are mostly spherical with very fine dendritic networks. This network might be a result of the rapid solidification, with a cooling rate of about 100 • C/s [26], during gas atomization process [18,27]. Non-etched powder particles were sectioned and imaged in Figure 4b to perform phase analysis.…”

Section: Microstructure Of the As-received Powdermentioning

confidence: 99%

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

193

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3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 • C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 • C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ -phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb 0.78 Ti 0.22 )C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.

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“…Following cooling and collection of the powder a sieving process was used to separate the powder into six size fractions, these being 212 -150 µm, 150 -106 µm, 106 -75 µm, 75 -53 µm, 53 -38 µm and < 38 µm. As particle size is the main determinant of cooling rate these span a range of cooling rates from approximately 250 K s -1 to 12,000 K s -1 [15].…”

Section: Methodsmentioning

confidence: 99%

“…Gas atomization would be expected to give cooling rates of the order 10 3 -10 5 K s -1 (see e.g. [15] and references therein) with catalytic activities in the subsequently activated catalyst more than twice that of conventional Raney-type Ni being reported [13].…”

Section: Introductionmentioning

confidence: 99%

Structure and phase-composition of Ti-doped gas atomized Raney-type Ni catalyst precursor alloys

2015

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Raney-type Ni precursor alloys containing 75 at.% Al and doped with 0, 0.75, 1.5 and 3.0 at.% Ti have been produced by a gas atomization process. The resulting powders have been classified by size fraction with subsequent investigation by powder XRD, SEM and EDX analysis. The undoped powders contain, as expected, the phases Ni 2 Al 3 , NiAl 3 and an Al-eutectic. The Ti-doped powders contain an additional phase with the TiAl 3 DO 22 crystal structure. However, quantitative analysis of the XRD results indicate a far greater fraction of the TiAl 3 phase is present than could be accounted for by a simple mass balance on Ti. This appears to be a (Ti x Ni 1-x )Al 3 phase in which higher cooling rates favour small x (low Ti-site occupancy by Ti atoms). SEM and EDX analysis reveal that virtually all the available Ti is contained within the TiAl 3 phase, with negligible Ti dissolved in either the Ni 2 Al 3 or NiAl 3 phases.

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Estimation of Cooling Rates During Close-Coupled Gas Atomization Using Secondary Dendrite Arm Spacing Measurement

Cited by 87 publications

References 24 publications

Microstructure evolution and mechanical properties of drop-tube processed, rapidly solidified grey cast iron

Microstructure evolution and mechanical properties of drop-tube processed, rapidly solidified grey cast iron

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Structure and phase-composition of Ti-doped gas atomized Raney-type Ni catalyst precursor alloys

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