Oscillatory instabilities and banded structures in rapidly solidified alloys

A phase-field study is presented to analyse the formation of the so-called banded structures in rapidly solidified alloys. We find that the emergence of these structures is due to an oscillatory dynamics of the solidification front driven by loss of interfacial equilibrium. The solidification pattern undergoes periodic transitions between dendritic and planar growth, as suggested by a phenomenological model, resulting in structures which are periodic along the growth direction. (C) 1999 Elsevier Science B.V. All rights reserved. PACS: 81.10.Aj; 05.70.Ln; 64.70.Dv.