Self-propagating crystallization waves in the TiCu amorphous alloy

Self-propagating crystallization waves are detected and experimentally demonstrated in the Ti50Cu50 amorphous alloy obtained by the melt spinning (ultrafast quenching) method. High-speed thermographic recording has shown that crystallization waves can appear spontaneously at the heating of an amorphous strip to 300-350A degrees D or at the local initiation by a hot tungsten coil of a small segment of the strip preliminarily heated to 230-250A degrees D. In the former case, the crystallization wave propagates at a velocity of similar to 7 cm/s; in the latter case, the crystallization wave propagates in a self-oscillation mode at an average velocity of similar to 1.2 cm/s. The temperature gradient across the wavefront is about 150A degrees D. The samples crystallized in the self-oscillation mode have a characteristic banded structure with a smaller grain in depression regions. The crystallization product in all samples is the TiCu tetragonal intermetallic phase.