FORMATION OF AMORPHOUS STRUCTURES AND THEIR CRYSTALLIZATION IN CU–TI SYSTEM BY HIGH-ENERGY BALL MILLING

Abstract

The paper presents the research findings on the formation of amorphous structures in the Cu–Ti system and their subsequent crystallization by highenergy ball milling (HEBM). Copper powders (PMS-V grade with an average particle size d = 45÷100 μm, GOST 4960-75) and titanium powders (PM99.95, d = 2,0÷4,5 μm, TU 48-19-316-80) were chosen as original components for obtaining Cu-Ti amorphous powders. The high-energy ball milling of Cu + Ti powder mixtures was carried out using the Activator- 2S laboratory planetary ball mill (disc rotation rate – 694 rpm; rotation rate of drums – 1388 rpm) for 1 to 30 minutes. The surface morphology and the micro-, nano- and atomic-crystalline structure of activated Cu + Ti powder mixtures were studied by X-ray diffraction (XRD) methods using the DRON-3M, diffractometer by scanning electron microscopy using the Zeiss Ultra + + microscope (Germany) with energy dispersive analysis, and by high resolution transmission electron microscopy (TEM) using the Titan microscope (USA). Thermal characteristics of phase transformations (temperature, heat of reaction, amorphouscrystalline transition) were determined by differential scanning calorimetry using the DSC 204 F1 instrument in a linear heating mode of up to450 °Cat a rate of 20 deg/min. Amorphous Cu-Ti powders were obtained by using high-energy ball milling for 20 min. According to X-ray diffraction data, the fraction of the amorphous phase in the material was 93 %. TEM-based studies showed that the material consisted mainly of an amorphous phase with an insignificant content of nanocrystalline regions sized from 2 to 8 μm. It was found that crystallization of the Cu–Ti amorphous phase occurred in the temperature range of 336–369 °C with the heat of reaction equal to 79,78 J/g.