THE EFFECT OF ULTRA-FINE ALLOYING ELEMENTS ON THE PHASE COMPOSITION, MICROSTRUCTURE, HIGH-TEMPERATURE STRENGTH AND FRACTURE TOUGHNESS OF Ti–Si–X AND Ti–Cr–X COMPOSITES

Advanced Ti-based composites are promising for applications in components of modern aircraft and rocket engines as well as other power equipment owing to their high strength-to-weight ratio and fracture toughness in a temperature range of 20 °C to 650 °C. 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, Sn, C) has been studied. For comparison, mechanical behavior of Ti–Cr–X composite (X=Al and/or C) has been studied. As-cast and thermo-mechanically deformed series of beam specimens were examined. Strength tests of specimens were performed under three-point bending in a temperature range of 20 °C to 1000 °C. Single-edge notch beam (SENB) tests under three-point bending of specimen series were carried out in a temperature range of 20 °C to 900 °C for estimating fracture toughness of materials. 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 achieving good high-temperature strength and fracture toughness of the studied composites was substantiated.