CRYSTALLIZATION PROCESS OF ELECTRON IRRADIATION-INDUCED AMORPHOUS PHASE IN NITI ALLOY

Electron irradiation at a low temperature produces the amorphous phase in NiTi alloy. The crystallization process of the amorphous phase was studied by means of in-situ experiment using HVEM. It is divided into three characteristic stages of the crystallization process. First, the broad and obscure boundary between the amorphous and the crystalline region becomes narrower and clearer. Second, the small crystals appear in the amorphous region near the boundary at 523 K. They grow towards the centre of the amorphous region with increasing the annealing temperature and the annealing time. The orientations of individual crystals are almost the same as the orientation before the irradiation.