The rare earth element cerium (Ce) was added to cast binary Ti-44 at.% Al a
lloys by arc melting in the range of 0.05 to 0.3 atomic percent. It was obs
erved that the as-cast structures of the ingots consisted of the usual thre
e zones of fine equiaxed grains near the mould wall, columnar grains growin
g away from the mould wall and coarse equiaxed grains near the center. Ce g
reatly promoted the growth of columnar grains and reduced their diameters.
The ingots were subsequently heat treated to obtain well-defined fully lame
llar structures. The material containing no rare earth displayed large equi
axed lamellar colonies of average size of > 1400 mu m; the material with 0.
05 at.% addition of Ce consisted of lamellar colonies of as fine as similar
to 440 mu m. The finest grain size of this material was 320 mu m at the to
p position in the ingot. (C) 2000 Kluwer Academic Publishers.