Physico-chemical nanomaterials science

Microstructure, high-temperature strength and fracture toughness of Ti–Si–X composites containing refractory phases
Vasyliv B.D.1, Kulyk V.V.2, Duriagina Z.A.2,3, Lyutyy P.Ya.2, Kovbasiuk T.M.2, Trostyanchyn A.M.2, Vira V.V.4, Vavrukh V.I.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.
4 Department of Strength of Materials and Structural Mechanics, Lviv Polytechnic National University, 12 S.Bandera str., Lviv 79000, Ukraine.

State-of-the-art Ti–Si–X composites are being developed for applications in modern aircraft and rocket engines as well as power equipment owing to their comparatively low specific weight and high strength and fracture toughness in a temperature range of 20–650 °C. This work is aimed at improving mechanical characteristics of the composites, namely, strength and fracture toughness, and increasing their operating temperature range up to 700−800 °C.
Ti–Si–X composites (X=Al and/or Zr) were manufactured with electron arc smelting. The content of alloying elements varied in a wide range (0.8–2.5 wt% Al, 5–8 wt% Zr). Strength tests of specimen series were carried out under three-point bending in a temperature range of 20 °C to 1000 °C. Fracture toughness tests of single-edge notch beam specimens were performed in a temperature range of 20 °C to 900 °C. The chemical and phase compositions of the composites were determined, as well as their microstructure and failure micromechanisms in relation to mechanical behavior were analysed.
Based on the dependences of strength and fracture toughness on testing temperature for the specimen series as well as the microstructure and failure micromechanism analyses, it was found that the Ti5Si3 and complex (Ti, Zr)5Si3 refractory phases play a crucial role in enhancing fracture toughness of all the specimen series in the high-temperature (700–800 °C) range.