Crystallization process of amorphous phase produced by ion irradiation in TiNi shape memory alloy

Thermal crystallization from amorphous TiNi has been investigated due to `in-situ' observation in a high voltage electron microscope. The specimens contained several types of nucleation sites, such as free surfaces, C-A interfaces and cracks, which enabled to comparing crystallization at each site. The heterogeneous nucleation developed at the specimen edge and the crystalline-amorphous interface, where the crystallization temperature depended on each nucleation sites. The crystal growth was liner relation at each temperature, and the activation energy from Arrhenius plot was evaluated as 2.7 eV. The preferential crystallization was observed also on precracked area, which implies some stress-assisted effect on the crystallization.