Investigation of the processes of formation of the crystalline phase in rapid-quenched layered amorphous-crystalline ribbons produced of Ti$_{50}$Ni$_{25}$Cu$_{25}$ alloy during electric pulse treatment

The effect of electric pulse treatment (EPT) on the microstructure of rapid-quenched layered amorphous-crystalline ribbons obtained by spinning a Ti$_{50}$Ni$_{25}$Cu$_{25}$ melt on a rapid rotating copper disk has been experimentally investigated. A sequential series of samples of Ti$_{50}$Ni$_{25}$Cu$_{25}$ alloy ribbons was obtained after EPT with a single pulse of electric current with a duration of 1 ms with an increase in the degree of heating after reaching the recrystallization temperature of the amorphous part of the ribbons at an electric current density $(J)$ from 680 to 891 A/mm$^2$. Studies of the microstructure of the cross-section of the treated samples and the calorimetric effects during the course of martensitic transformations (MT) have shown that the magnitude and nature of MT are consistent with the observed microstructure of ribbons after EPT with varying degrees of annealing. An increase in $J$ during EPT and overheating leads to the formation of a more homogeneous crystal structure, characterized mainly by columnar crystals, and an increase in MT temperature. The peak temperature of the austenitic transformation in the treated samples, depending on the increase in $J$, increases from 39.0$^\circ$C in the initial state to 64.5$^\circ$C at $J$ = 891 A/mm$^2$.