RECRYSTALLIZATION AND GRAIN-GROWTH IN A B2 IRON ALUMINIDE ALLOY

Recrystallization and grain growth were studied in hot extruded B2 Fe- Al by X-ray texture measurements and Orientation Imaging Microscopy (O IM). As-extruded material contained ultra-fine grains of 02-04 mu m. S uch grains contained high dislocation densities, but mostly possessed high angle boundaries with the immediate neighbors. Depending on the a nnealing conditions, a combination of fine equiaxed and/or large colum nar grains was observed. The fine equiaxed grains were at least 10 tim es larger than the as-extruded grain size and contained lower dislocat ion densities-which points towards primary recrystallization. Large co lumnar grains were observed in samples with fast heating and/or prolon ged annealing at higher temperatures and were possibly formed by grain growth. Samples with predominantly equiaxed grain structure contained a similar texture as in the as-extruded material-a strong [110] fiber . Formation of the large columnar grains reduced the [110], but increa sed the [111] fiber. Possible selection of [111] grains for grain grow th is not due to grain size advantage, as grain size distributions of all three fibers were similar, but can be understood from the consider ation of grain boundary character distribution (GBCD) or mesotexture. (C) 1998 Elsevier Science Limited. All rights reserved.