Modeling of solidification of molten metal droplet during atomization

Abstract

A mathematical model to describe the solidification behavior of an atomized droplet during flight, in terms of nucleation temperature, recalescence temperature, nucleation position, solid fraction at nucleation temperature, and droplet temperature and velocity, is formulated. The concept of transient nucleation is applied to model the short nucleation event. A maximum droplet velocity exists, beyond which the droplet velocity shows an inflection phenomenon during the flight. The velocity of smaller droplets is higher at a shorter flight distance and lower at a longer flight distance. Variations of the gas flow patterns have more effects on smaller droplets, and the effects are more significant at a longer flight distance. A minimum surface heat-transfer coefficient exists as the droplet flies. Prior to nucleation or recalescence, smaller droplets have lower temperature at a given flight distance. Smaller droplets have lower nucleation temperature. Medium-size (around 80-m) droplets fly over the shortest flight distance before the nucleation starts. Smaller droplets have a larger solid fraction at the end of recalescence. Atomization gas has more effects on the droplet momentum than on the heat content of the droplet.

Thermal Stability and Mechanical Properties of Spray-Formed and Melt-Spun Al<SUB>89</SUB>La<SUB>6</SUB>Ni<SUB>5</SUB> Metallic Glass Matrix Composites

“…Spray forming process [11][12][13][14] has been increasingly used to produce these composites in bulk dimension. [13][14][15][16] In this study, an as-spray-formed Al 89 La 6 Ni 5 nanophase composite 13) mixed together with 30% primary crystals (1 mm in diameter) was produced.…”

Microstructural evolution in spray-formed and melt-spun Al85Nd5Ni10 bulk hybrid composites

“…Spray forming [8][9][10][11] is a rapid solidification process in which the molten metal are atomized into fine droplets by high pressure nitrogen gas and then collected into a dense deposit on the substrate after a short flight distance. Its most attractive features are the ability to create refined microstructure and reduced segregation [12].…”

Microstructure and mechanical properties of a spray-formed Ti-based metallic glass former alloy

“…Spray forming makes different microstructure to different areas of the deposit because of different cooling rates during solidification and further thermal treatment from the successively deposited powders or droplets [10]. In order to analyze the structure development, the center, i.e.…”

“…On the other hand, spray forming [9][10][11][12][13][14][15] with the characteristic of rapid solidification, has been developed for the manufacture of near-net shape products. In the spray forming process, high pressure inert gas converts liquid metal stream into variously sized droplets.…”