Physico-chemical nanomaterials science

The effect of ultra-fine alloying elements on high-temperature strength and fracture toughness of Ti–Si–X composites
Vasyliv B.D.1, Duriagina Z.A.2,3, Kulyk V.V.2, Vavrukh V.I.2, Lyutyy P.Ya.2, Kovbasiuk T.M.2, Lemishka I.A.2
1 Department of Hydrogen Technologies and Alternative Energy Materials, Karpenko Physico-Mechanical Institute of the NAS of Ukraine, 5 Naukova str., Lviv 79060, Ukraine.
E-mail: mechengin1111@gmail.com
2 Department of Materials Science and Engineering, Lviv Polytechnic National University, 12 S.Bandera str., Lviv 79000, Ukraine.
3 Department of Materials Engineering, The John Paul II Catholic University of Lublin, 14 Racławickie Al., Lublin 20-950, Poland.

In contrast to conventional titanium alloys, an operating temperature of which is limited by 300–500 °C, advanced Ti-based composites possess high fracture toughness and strength under bend and tensile loading in the temperature range of 20 °C to 650 °C. Owing to their high strength-to-weight ratio, these composites are promising for applications in components of modern engines (aircraft, rocket, and internal combustion ones) as well as other power equipment (compressors, gas turbines, etc.).
However, there is a need to increase their operating temperature range up to 700−800 °C. In this work, mechanical behavior of Ti–Si–X composites (X=Al and/or Zr) have been studied in a temperature range of 20 °C to 800 °C. The content of alloying elements varied in a wide range (2–5 wt% Al, 2–5 wt% Zr). The composites were manufactured with electron arc smelting. As-cast and thermo-mechanically deformed series were examined. Beam specimens were cut of blanks, grinded, and polished to reach a good surface quality. Fracture toughness tests of specimen series were performed at a temperature of 20 °C using an indentation method. After that, single-edge notch beam tests under three-point bending of specimen series were carried out in a temperature range of 20 °C to 800 °C. Strength tests of specimen series were performed under three-point bending in a temperature range of 20 °C to 800 °C. Based on the constructed dependences of fracture toughness and strength on testing temperature for the specimen series as well as the microstructure and failure micromechanism analyses, the role of ultra-fine alloying elements in retaining high-temperature strength and fracture toughness of Ti–Si–X composites was substantiated.