A cellular structure has been produced in a directionally solidified Fe-4.34 wt.% Ni alloy. Double instability at the cell tip was revealed and described as a first harmonic wave of the fundamental undulation. The Ni solute redistribution was measured just above the bottom of the tip splitting. An increase of the solute content corresponds well to the location of the tip splitting. The presence of ferrite (delta) and initiation of (delta)/austenite (gamma) transformation have been confirmed by the use of automatic crystal orientation mapping. A continuous disappearance of the subgrain structure with decreasing temperature and increasing contribution of delta/gamma transformation was observed. (C) 2003 Elsevier Science B.V. All rights reserved.