Impact of Microstructure on the Mechanical Behavior of Ti–Al–Ni Composite in a Wide Temperature Range (20–800 °C)

Titanium based composites are widely used for manufacturing critical high-temperature components of rocket and aircraft engines as well as power generation equipment. They have advantages over conventional titanium alloys in operating temperature which can be higher by 150–350 °C exhibiting thus improved temperature stability and comparatively high fracture toughness at elevated temperatures. Therefore, they can operate in a temperature range of 20 °C to above 700 °C. This work is aimed at studying the effect of microstructure on mechanical behavior of Ti–Al–Ni composite in a wide temperature range (20–800 °C). Ti–Al–Ni composite was manufactured by melting using an electric arc furnace. Chemical composition of the material was as follows: Al (1.8 wt%), Ni (40 wt%), Ti (balance). Beam specimens were cut from ingots, ground, and polished to reach a satisfactory surface quality. Then, a fracture toughness test of single-edge notch beam specimens was performed in a temperature range of 20–800 °C. The microstructure and fractographic studies were carried out using a scanning electron microscope. The phase composition of the material was also estimated. Peculiarities of a temperature-dependent change in fracture toughness of the composite were then analyzed and related to its microstructure and fracture micromechanisms. A significant increase in fracture toughness of the material was revealed in a temperature range of 700–800 °C. The role of separate phases in reaching such a high level of fracture toughness for Ti–Al–Ni composite was discussed. This material is regarded to be promising for high-temperature (700–800 °C) applications.