Temperature Dependences of the Mechanical Properties of Microlayer Ti/TiAl3 Composites Under Cyclic Loading

The paper examines three microlayer Ti/TiAl3 materials of initial Ti-Al composition, which were produced through reactive sintering and rolling of packets consisting of alternating titanium and aluminum ribbons of varying thickness at 600, 700, and 770 & DEG;C. Young's modulus of these materials was determined under longitudinal vibrations at room temperature with a frequency of about 45 kHz and under resonant bending vibrations at high temperatures ranging from 20 to 820 & DEG;C with a frequency a hundred times lower. The temperature dependences of the elastic modulus E for the microlayer materials exhibited slopes between those of the dependences for titanium and the well- known VT25U alloy. The Ti/TiAl3 materials were heated and held at 700 & DEG;C to result in a material with stable E values, surpassing those of the VT25U alloy at temperatures up to 700 & DEG;C. The dependences of stresses in the samples on the relative power of the test installation were determined at constant temperatures of 650 and 700 & DEG;C for the microlayer Ti/TiAl3 and VT25U materials. The microlayer materials dissipated a significantly larger portion of mechanical vibration energy than the heat-resistant VT25U material. The difference in the fatigue resistance mechanisms for the microlayer and isotropic materials at high temperatures is not solely attributed to their distinct temperature dependences of Young's modulus at atomic interaction levels. The difference primarily arises from the variation in temperature-dependent cyclic strains associated with dislocations at microstructural and macrostructural levels. A fatigue crack is shown to delaminate the material in the middle of the intermetallic layers.