Production of Rapidly Solidified Al–Si Alloy Powder by the Rotating-Water-Atomization Process and Its Structure

Abstract

The rotating-water-atomization process developed by the authors was applied to production of rapidly solidified powder containing Si between 7.1% and 23.7%. The particle shape was not spherical but tear-drop-like. The size distribution and the mean particle diameter were independent of Si content. The structure of an as-atomized particle was composed of finely dispersed Al and/or Si primary crystals in the eutectic matrix, and primary Si was hardly observed for Si contents less than 16%Si. The number of primary Si increased with increasing Si content. The variation, with Si content, of the lattice parameter of as-atomized particles showed a minimm at 16.3%Si. Two exothermic reactions were observed at about 500 K and 650 K, respectively, by DSC thermal analysis. Heat generatd at about 500 K was maximum at 16.3%Si and it was consistent with the lattice parameter variation. Coarsening of Si crystals at 723 K was very fast at the initial stage of annealing, and afterwards it was proportional to t1/3.

Chemical leaching of rapidly solidified Al–Si binary alloys

“…1(b) was formed by either microsegregation of Si in the primary ␣-Al phase during rapid solidification or the existence of a little Si phase. These results agreed with our previous results [11]. …”

“…3. The exothermic reaction was due to the precipitation of the Si phase from the supersaturated ␣-Al phase as described in a previous paper [11]. The total heat generated by the exothermic reaction was evaluated from the hatched area in Fig.…”

“…There are only few reports on leaching for this system. A highly supersaturated ␣-Al(fcc) solid solution of Si can be obtained by rapid solidification [11]. The supersaturated ␣-Al solid solution means that the Si atoms substitutionally occupy the lattice sites of the ␣-Al phase.…”