The present paper has shown that the brittle-to-ductile transition in TiAl
intermetallic ought to be considered as a two-stage phenomenon: (1) first n
oticeable increase in ductility (at T(1)degrees C) is controlled by thermal
ly activated relaxation processes in grain boundaries. In this case, the br
ittle fracture type is retained; (2) following an increase in ductility (at
T-2 = T-1 + Delta T) is caused by thermally activated relaxation processes
within the grains (in addition to ones in grain boundaries) which lead to
the transition from brittle fracture to ductile one. (C) 1999 Elsevier Scie
nce Ltd. All rights reserved.