Ti-Y2O3 Composites with Nanocrystalline and Microcrystalline Matrix

Mechanical milling of a Ti-2 pct Y 2 O 3 powders mixture led to the synthesizing of a composite powder with a nanocrystalline Ti matrix having a mean crystallite size of 19 nm. Both the nanocomposite powder prepared through milling and the initial mixture of powders were consolidated by hot pressing under the pressure of 7.7 GPa at the temperature of 1273 K (1000 °C). The transmission electron microscopy (TEM) investigations of the bulk sample produced from milled powder revealed that Y 2 O 3 equiaxial particles of less than 30 nm in size are distributed uniformly in the Ti matrix with a grain size in the wide range from 50 nm to 200 nm. The microhardness of the produced nanocrystalline material is 655 HV0.2, and it significantly exceeds the hardness of the microcrystalline material (the consolidated initial mixture of powders), which is equal to 273 HV0.2. This finding confirms that reducing the grain size to the nanometric level can have a beneficial influence on the hardness of titanium alloys. Dispersion hardening also contributes to the hardness increase.