Crystallization of Ti33Cu67 metallic glass under high-current density electrical pulses

Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, Kutateladze str, 18, Novosibirsk 630128, Russia. .
Nanoscale Research Letters (Impact Factor: 2.78). 08/2011; 6(1):512. DOI: 10.1186/1556-276X-6-512
Source: PubMed


We have studied the phase and structure evolution of the Ti33Cu67 amorphous alloy subjected to electrical pulses of high current density. By varying the pulse parameters, different stages of crystallization could be observed in the samples. Partial polymorphic nanocrystallization resulting in the formation of 5- to 8-nm crystallites of the TiCu2 intermetallic in the residual amorphous matrix occurred when the maximum current density reached 9.7·108 A m-2 and the pulse duration was 140 μs, though the calculated temperature increase due to Joule heating was not enough to reach the crystallization temperature of the alloy. Samples subjected to higher current densities and higher values of the evolved Joule heat per unit mass fully crystallized and contained the Ti2Cu3 and TiCu3 phases. A common feature of the crystallized ribbons was their non-uniform microstructure with regions that experienced local melting and rapid solidification.
PACS: 81; 81.05.Bx; 81.05.Kf.

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    ABSTRACT: Heating of conductive materials by electric current is used in many technological processes. Application of electric pulses to metallic glasses induces their fast crystallization, which is an interesting and complex phenomenon. In this work, crystallization of the Fe83B17 amorphous alloy induced by pulses of electric current produced has been studied using X-ray diffraction and transmission electron microscopy. Ribbons of the alloy were directly subjected to single pulses of electric current 250 µs long formed by a capacitor discharge. As the value of \(\smallint I^{2} {\text{d}}t\) was increased from 0.33 to 2.00 A2 s, different crystallization stages could be observed. The crystallization began through the formation of the nuclei of α-Fe. At high values of \(\smallint I^{2} {\text{d}}t\), α-Fe and tetragonal and orthorhombic Fe3B and Fe23B6 were detected in the crystallized ribbons with crystallites of about 50 nm. Thermal annealing of the ribbons at 600 °C for 2 min resulted in the formation of α-Fe and tetragonal Fe3B. It was concluded that pulses of electric current produced by a capacitor discharge induced transformation of the Fe83B17 amorphous phase into metastable crystalline products.
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