Peculiarities of Microstructure Evolution and Property Changes of Titanium Alloys In Situ during Electric Forging

The experimental studies of the parameters of hot electric forging were carried out on industrial heat resistance (α + β), (near-α), and (α″ + β) titanium alloys. It was established that simultaneous fast Joule heating with a high-density electric current and an initial temperature of hot intense plastic deformation are important parameters for the electric forging of heat resistance titanium alloys. The heating rate dependence on electric current density and thermophysical properties of metal, as well as deformation temperature dependence on axial compression stress and mechanical strength of heated metal under compression as the main parameters of electric forging, were chosen. To calculate the processing parameters, we investigated the evolution of the thermophysical properties and mechanical strength of selected titanium alloys at a heating rate of 50°C·s−1 at a temperature up to 1,200°C. Microstructural evolution and the phase transformation temperature were determined using optical and scanning electron microscopes. The results show that the grinding efficiency of the coarse-grained microstructure depends on the increase of the heating rate, and the formation of uniaxial ultrafine alpha-phase grains depends on an increase of the compressive stress or decrease in the deformation temperature. It can be argued that the compressor blades made of titanium alloys for aircraft turbojet engines had increased ductility, stability, and high-cyclic fatigue strength, as well as increased operating life at ambient temperatures. The results can be used to model and calculate the rational parameters of electric forging to improve the operational properties of the final products.