A study of precipitation in DO3 ordered Fe-Al-Nb alloy

Precipitation and ordering has been examined in Fe3Al-base alloy with a small addition of Nb. At low temperatures the alloy shows DO3 order with no precipitation, at least for short annealing times. At intermediate temperatures, 700-750 degrees C, planar precipitates of a phase with L2(1) structure form, which transform at longer times and high temperatures to blocky precipitates of the stable Laves phase of C14 structure. The L2(1) precipitates form on {001} planes, coherently with the ordered matrix, while the C 14 particles form in a {(1) over bar 010}(C14)//{(1) over bar 01}(matrix) relationship with < 1 (2) over bar 1o >(C14) approximately parallel to the < 010 >(matrix) and < 0001 >(C14) approximately parallel to the < 101 >(matrix). These particles grow relatively quickly in the intermetallic matrix, and hence are unsuitable for matrix strengthening at temperatures above about 750 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.