Details

Autor(en) / Beteiligte

• Johnston, M.H.
• Griner, C.S.
• Parr, R.A.
• Robertson, S.J.

Titel

The direct observation of unidirectional solidification as a function of gravity level

Ist Teil von

• Journal of crystal growth, 1980-01, Vol.50 (4), p.831-838

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

1980

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• A saturated solution of NH 4 Cl-H 2O was solidified unidirectionally on Earth at 1 g and in a suborbital rocket at 10 -5 g. In the 1 g experiment, extensive fluid flow was apparent, creating plumes which carry numerous crystallites vertically above the interface in a manner usually attributed with causing freckling in castings. During growth the interface grew into the liquid at the same rate as the individual dendrites. When solidified in low g the interface grew at a slower rate than the individual dendrites. No plumes of liquid carrying crystals were seen, but several crystals did appear and grow ahead of the interface. Growth rates, dendrite morphologies and preferred crystallographic orientations are compared for the two experiment conditions. Results indicate that solidification in low gravity produces more uniform dendrite arm spacings, and tends to be controlled by diffusion and crystallographic orientation.