Formation of Amorphous Structures and Their Crystallization in the Cu–Ti System by High-Energy Ball Milling

Abstract

The results of the investigation into the formation of amorphous structures in the Cu–Ti system and their subsequent crystallization under the effect of high-energy ball milling (HEBM) are presented. To form amorphous Cu–Ti powders, powders of copper (MPS-V grade with average particle size d = 45–100 μm, GOST (State Standard) 4960–75) and titanium (PM99.95, d = 2.0–4.5 μm, TU (Technical Specifications) 48-19-316–80) are selected as the initial components. The HEBM of Cu + Ti powder mixtures is performed using an Aktivator-2S laboratory planetary ball mill (at revolution rates of discs of 694 rpm and drums of 1388 rpm) for 1–30 min. The investigations into the surface morphology and micro-, nano-, and atomic crystalline structure of activated Cu + Ti powder mixtures are fulfilled by X-ray structural analysis (XSA) using a DRON-3M diffractometer, scanning electron microscopy using a Zeiss Ultra+ microscope (Germany) with the application of energy dispersive analysis, and high-resolution transmission electron microscopy (TEM) using a Titan microscope (United States). The determination of thermal characteristics of phase transformations (temperature, heat of reaction, and amorphous-to-crystalline transition) are performed by differential scanning calorimetry using a DSC 204 F1 device in the mode of linear heating to 450°C at a rate of 20 K/min. The Cu–Ti amorphous powders were fabricated using HEBM for 20 min. The XSA data evidence that the fraction of the amorphous phase in the material was 93%. The TEM investigations showed that the material preferentially consists of the amorphous phase with an insignificant content of nanocrystalline regions 2–8 nm in size. It is found that the Cu–Ti amorphous phase crystallizes in a temperature range of 336–369°C, and the heat of reaction is 79.78 J/g.