Titanium plate is widely recognized for its high strength, light weight, good structural rigidity and other advantages.High strength titanium alloy ti-6 al-4v can be used not only in aviation field, but also as an important candidate material for structural parts in automobile, chemical industry and other industrial fields.The formability of ti-6al-4v alloy sheet at room temperature is very limited, and the rebound after forming is very large, which brings many problems to traditional stamping and pressure forming.
Although the forming limit of ti-6al-4v alloy sheet will be increased and the rebound will be reduced under high temperature, the forming at room temperature still has great advantages in cost saving.Rolling forming is a kind of forming method which USES the rotating roll to make the metal blank deform step by step to make the workpiece, which is suitable for the structural parts with high strength and limited formability.
Because the springback Angle of the material is small in the process of rolling forming and springback compensation can be carried out by a simple and feasible method, rolling forming is an effective method for room temperature forming of ti-6al-4v alloy sheet.To this end, Ossama et al. conducted a laboratory study on the forming and springback behavior of 2 mm thick and high strength ti-6 al-4v alloy plates at room temperature after annealing at 820 ℃.
The original microstructure of the selected ti-6al-4v alloy plate was composed of 93.86% isoaxial phase and 6.14% fault phase, with an average grain size of 1.3 cm ±0.7 cm.The results of the tensile test at room temperature showed that when the anisotropy was large and the rolling direction was 45°, the yield strength of the sample was the lowest, the elongation was higher, and when the ultimate strength was reached, the sample would break quickly.The forming limit test was completed on the equipment equipped with hemispherical punch with a diameter of 60 mm.Autogrid Vario, an optical strain measurement system with four advanced CCD cameras, was used to record the complete deformation history of each sample.The deformation behavior of different strain paths was tested by designing different sample shapes.
It was found that all samples suddenly broke at the top of the hemispherical punch without obvious necking before breaking, indicating that the formability of the alloy at room temperature was very limited.The deformation behaviors of Ti-6Al-4V alloy sheet during bending and rolling were analyzed.
The results showed that the minimum bending radius of the pendulum folding bending test and v-die bending test was 9 mm, while the minimum bending radius of the rolling was 7.51 mm, an increase of more than 15%.Rolling forming allows for smaller radius sizes and less springback than simple bending forming.This is mainly due to the fact that rolling forming is a multi-step cumulative deformation process, and the progressive multiple deformation can inhibit the crack growth, and make the material deformation more sufficient than the ordinary single deformation.
In addition, the shape defects frequently occurred in the rolling process of high strength steel are relatively rare in the rolling process of ti-6al-4v alloy.It can be seen that rolling forming is a potential process of high strength titanium alloy plate for aerospace and automotive structural parts.