The process of amorphization induced by electron irradiation in alloys

Amorphization induced by electron irradiation in Ni–50 at% Ti crystals has been investigated by electron microscopy. In order to clarify successive stages of amorphization, micrographs were taken in vairous regions where the total dose of electrons was continuously changed. Contrast was manipulated by changing the reflecting condition. Results obtained are summarized as follows: (a) Amorphization occurs inhomogenously; (b) there is a critical size, i.e., about 5 nmø in the crystals, for observing sharp lattice images in small blocks; (c) lattice images change to short and wavy fringe contrasts when the block size becomes smaller than the critical one, and finally they disappear; and (d) boundary contrast of the blocks rapidly decreases with decreasing size, and is hardly observed when the size becomes smaller than the critical one. Based on the results, the cause of abnormal fringe contrasts in fine blocks, the amorphization process, and atomic structures of amorphous materials are discussed.