Self-propagating crystallization waves in the TiCu amorphous alloy

Self-propagating crystallization waves are detected and experimentally demonstrated in the Ti$_{50}$Cu$_{50}$ 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 300–350$^\circ$C or at the local initiation by a hot tungsten coil of a small segment of the strip preliminarily heated to 230–250$^\circ$C. In the former case, the crystallization wave propagates at a velocity of $\sim$7 cm/s; in the latter case, the crystallization wave propagates in a self-oscillation mode at an average velocity of $\sim$1.2 cm/s. The temperature gradient across the wavefront is about 150$^\circ$C. 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.