Hot forming technology of titanium alloy
At present, metal plastic deformation can be divided into cold forming (below recrystallization temperature and no recovery process), hot deformation (above recrystallization temperature) and warm deformation (between the above two) according to the working temperature of material plastic deformation. In the forming process of titanium alloy sheet, hot forming is the most mature and widely used forming technology, mainly including electric furnace heating, resistance heating and induction heating methods.
The hot forming technology of titanium alloy is to heat the titanium alloy plate to the proper forming temperature, using the characteristics of plastic deformation softening of titanium alloy at high temperature (yield strength drop, elongation increase), to achieve the forming of complex titanium alloy parts. At present, the research on hot forming of titanium alloy is mainly focused on forming equipment, forming process, microstructure, forming performance and forming limit.
Titanium alloy pulse current assisted forming technology
Since the 1990s, a large number of experiments and theoretical studies have been carried out on electroplasticity of Al, Ti, Ni, Cu and other materials, and a series of related electroplasticity effect theories have been put forward.
Compared with joule thermal effect of traditional heat-assisted forming, electric-assisted forming technology also has pure electroplastic effect, skin effect and magnetic compression effect, that is, electric-thermo-mechanical coupling effect of multiple fields, which has an impact on the microstructure and mechanical properties of materials. At the same time, the current assisted forming process has the advantages of low equipment complexity, fast heating rate, high electric-thermal conversion rate, high heating uniformity, and has a broad development prospect in the field of plastic processing of room temperature metal difficult to form, and is expected to be applied in bending, drawing, rolling, bulging, progressive forming and other forming processes.
Electromagnetic assisted forming technology of titanium alloy
Electromagnetic forming technology is a high rate forming method which makes use of metal plastic deformation under the action of magnetic force in strong pulse magnetic field. In order to analyze the structural response of Gr.5 titanium alloy plate under different deformation speeds, Li et al. studied the microstructure under high-speed deformation and compared it with that under quasi-static deformation. They found that under dynamic loading, the grain size of Gr.5 titanium alloy plate did not change significantly, but the grain was elongated. Due to material flow and impact, the hardness distribution of samples is not uniform, but the texture does not change significantly.
In Gr.5 titanium alloy high-speed deformation process, when the deformation is small, the plastic deformation is dominated by dislocation slip mechanism. When the amount of deformation increases, in addition to dislocation slip mechanism, twinning mechanism is also activated, and the twinning plane is (1011), which is conducive to plastic deformation, but the number is small.