Abstract
This paper presents a new production method for a spherical and monocrystalline aluminum powder. Aluminum powder of irregular particle shapes was mixed with silica nanoparticles and heated to a temperature above the melting point of aluminum. Due to its molten state, high surface tension, and poor wettability, the aluminum particles were transformed into liquid and spherical droplets separated by silica nanoparticles. The spherical shape was then retained when the aluminum particles solidified. The influence of the processing temperature on the particle shape, phase composition, and microstructure was investigated. Moreover, calorimetric, X-ray diffraction, grain size, and scanning electron microscopy with electron backscatter diffraction (SEM-EBSD) measurements of the particles’ microstructure are presented. It is proven that, by this means, a spherical and monocrystalline aluminum powder can be efficiently created directly from an air-atomized irregular powder. The observed phenomenon of particles becoming round is of great importance, especially when considering powder preparation for powder-based additive manufacturing processes.
Highlights
A large and growing interest is focused on powder-based additive manufacturing, especially among those industrial fields where the method can be of great importance, such as aviation or high-end motor vehicles [1]
We report a secondary powder-processing method allowing for the rounding of irregular powder particles by utilizing the combination of the properties listed above
Silica was used as a separator among the aluminum particles in order to prevent their agglomeration at elevated temperatures
Summary
A large and growing interest is focused on powder-based additive manufacturing, especially among those industrial fields where the method can be of great importance, such as aviation or high-end motor vehicles [1]. For individual industrial applications, such as the manufacture of metal parts through metal injection molding, selective laser melting (SLM) or combustion, characteristics such as shape and particle-size distribution are basic requirements among many others, e.g. bulk chemical composition, surface composition, and cohesion [2,3,4,5]. Used industrial methods of manufacturing spherical (or nearly spherical) aluminum powders are heretofore based on thermal spraying, plasma spraying, or other physical means of disrupting the molten metal into separate droplets [3,8,9]. These widely used powder manufacturing methods are characterized by some deficiencies, including high energy consumption and their complexity. The products are often characterized by a wide particle-size distribution
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