2-DIMENSIONAL CHARACTER OF AN AMORPHOUS STATE IN A EUTECTOID REACTIONOF A TI-40 AT PERCENT AL-ALLOY

Morphological and crystallographic features of an amorphous state appe aring in an initial stage of a eutectoid reaction in a Ti-40 at. % Al alloy have been investigated by transmission electron microscopy. Dark field images with different electron incidences, which were taken by using a part of a halo ring, indicate that the shape of the amorphous- state region is basically a plate, the normal of which is parallel to the [00.1] direction of the D0(19) structure. In addition, lattice fri nges corresponding to the (00.2) plane are often observed in the amorp hous region. On the basis of these data, it is concluded that a lattic e destruction in the amorphous region mainly occurs in the (00.1) plan e of the D0(19) matrix.