Solidification and microstructure evolution during spray atomization and deposition of Ni3Al

In this article, the thermal history and cooling rate experienced by gas-atomized Al-based amorphous powders were studied via numerical simulations. Modeling simulations were based on the assumption of Newtonian cooling with forced convection, as well as an energy balance, which involves gas dynamics, droplet dynamics, and heat transfer between gas and droplet. To render the problem tractable, phase transformations, crystal nucleation, and growth were not taken into account in the analysis of the solidification of Al droplets; instead, an energy balance approach was formulated and used. The numerical results and associated analysis were used to optimize processing parameters during gas atomization of Al-based amorphous powder. The results showed that the cooling rate of droplets increases with decreasing powder size and can reach in excess of 10 5 K/s for powder <20 lm in diameter. Gas composition has a more significant influence on cooling rate than gas pressure, and 100 pct He has the highest cooling effect. The results also showed that the cooling rate increases with increasing melt superheat temperature.

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“…[21,[26][27][28][29] The mass probability density function p(d) of the droplet-size distribution can be expressed by [30][31][32] …”

Section: A Droplet Size Distributionmentioning

confidence: 99%

Gas Atomization of Amorphous Aluminum: Part I. Thermal Behavior Calculations

Zheng

Lin

Zhou

et al. 2009

Metall Mater Trans B

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“…Then the high temperature annealing in the mushy zone [44][45][46] or the low cooling rate (<10 K/s) within the asdeposited preforms [44,46,47] …”

Section: Discussion Of the Phase Transformation And Microstructural Fmentioning

confidence: 99%

Microstructure modification and related mechanism of spray‐formed Fe‐bearing hypereutectic Al‐Si alloys

Hou

Cai

Cui

et al. 2010

Materialwissenschaft Werkst

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The Fe-bearing hypereutectic Al-Si alloys with/without Cr/(Cr+Mn) addition have been prepared by Spray Forming (SF) process. With 2 wt.% Cr addition, the short-rod b-Al 5 FeSi phase in sprayformed Al-25Si-5Fe-3Cu (wt.%, denoted as 3C) alloy can be substituted by particulate aAl(Fe,Cr)Si phase with sizes less than 5 -6 lm. But small quantity of blocky b-Al 5 (Fe,Cr)Si phase still appears in Cr-added hypereutectic Al-Si alloy. When (2Cr+1Mn) (wt.%) are added simultaneously into 3C alloy, almost all the short-rod b-Al 5 FeSi phase or blocky b-Al 5 (Fe,Cr)Si phase disappear, instead, the a-Al(Fe,Cr,Mn)Si phase become the only Fe-bearing phase. During heat treatments, the other two spray-formed hypereutectic Al-Si alloys (besides SF-3C alloy) are thermodynamically stable for the appearance of high thermodynamically stable particulate aAl(Fe,Cr)Si/a-Al(Fe,Cr,Mn)Si phase. Also the phase transformation occurred during the heating/ cooling process of the present hypereutectic Al-Si alloys are investigated and the mechanism of microstructural formation of the spray-formed alloys are discussed.Keywords: Spray Forming / hypereutectic Al-Si alloy / microstructure / thermal stability / phase transformation / Schlüsselwörter: Sprühkompaktieren / hypereutektische Al-Si-Lebierung / thermische Stabilität / Phasenumwandlung /

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“…The gas velocity during impact on the melt stream and the gas flow rate ( depend on atomization pressure and the design of ⅐ G) the atomizer, which can be estimated as follows. On the basis of earlier studies on atomization nozzles used in our laboratory, [27] these types of nozzles can be treated as convergent-divergent ones. It is assumed that the atomizer manifold is large enough so that the velocity of gas in the manifold is considered to be nearly zero.…”

Section: Gas Atomized Droplet Size Distributionmentioning

confidence: 99%

“…The droplet size distribution for a variety of gas-atomized metals and alloys has been widely reported to follow a lognormal distribution. [2,[23][24][25][26][27][28] Accordingly, the mass probability density function (g(d )) of droplet size distribution can be expressed as follows: [29,30,31] …”

Section: Gas Atomized Droplet Size Distributionmentioning

confidence: 99%

Modeling of porosity during spray forming: Part I. Effects of processing parameters

Cai

Lavernia

1998

Metall Mater Trans B

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In this article, a porosity model is developed based on particle packing theory, fluid mechanics, and particle thermal and dynamic behavior during spray forming. According to this model, the amount of porosity in as-deposited materials can be estimated on the basis of the average fraction of solid in the incident spray and the solid particle packing density. A porosity coefficient ⌽ is introduced. By using this model, the effects of deposition distance, atomization gas pressure, melt flow rate, and melt superheat on porosity are investigated. The amount of porosity demonstrates distinct V-shaped variations with the processing parameters. Finally, the optimal processing parameters for achieving low porosity are discussed on the basis of the calculated results.

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Solidification and microstructure evolution during spray atomization and deposition of Ni3Al

Cited by 68 publications

References 21 publications

Gas Atomization of Amorphous Aluminum: Part I. Thermal Behavior Calculations

Gas Atomization of Amorphous Aluminum: Part I. Thermal Behavior Calculations

Microstructure modification and related mechanism of spray‐formed Fe‐bearing hypereutectic Al‐Si alloys

Modeling of porosity during spray forming: Part I. Effects of processing parameters

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