Structural Change with Heat Treatment in the Mechanically Alloyed Cu-Ti-B Powder

Abstract

Mixtures of copper, titanium and boron powders with various contents were mechanically alloyed for 72ks by using a ball mill, and then isothermally heat-treated at the temperautre range of 673K to 1183K. For the discussion on the precipitation process in the mechanically alloyed powder, microstructural changes in the powder with the heat treatment were investigated by means of powder technique and smallangle scattering technique in the X-ray diffraction. In an early stage of the heat treatment at 673-873K, the mechanically alloyed powders form a modulated structure, i.e. existence of zone which have a well-defined interface between matrix and solute-enriched regions. Diameter of the zones formed in the powder heat-treated for 3.6 ks at these temperature range is about 6-7nm. After the heat treatment for a long time, titanium boride particles such as TiB₂, Ti₂B₅ and Ti₃B₄ form in the mechanically alloyed particles. The formation of these intermetallic compounds is accelerated with the increasing of treating temperature.