Process Optimization and Performance Analysis of Ti-B25 Titanium Alloy Tube Extrusion
In order to accelerate the application of Ti-B25 titanium alloy in ship communication systems, this study used DEFORM-3D finite element software to simulate the tube extrusion process under the conditions of deformation temperature of 900℃ and strain rate of 0.1 s^-1 based on the constitutive equation established in the early stage and the process parameters optimized by the hot working diagram, and verified it through actual extrusion experiments. The results show that under this process condition, a Ti-B25 titanium alloy tube billet with a diameter of 62 mm × 12 mm was successfully extruded, with excellent surface quality and recrystallized grains in the structure. After solution aging treatment at 830℃/1h + 600℃/8h, the tube billet showed excellent strength-plasticity matching, which fully met the use requirements of ship antenna tubes.
I. Finite element model construction
1. Geometric model
Figure 1 shows a schematic diagram of the extruded billet and the die. The three-dimensional model of the billet, extrusion cylinder, and extrusion rod was constructed using SolidWorks software and converted into an STL file that can be recognized by DEFORM-3D software.
In order to improve the calculation efficiency, only 1/4 of the tube was finely meshed (see Figure 2) to ensure the accuracy and convergence of the simulation process.
2. Constitutive model
Based on the previous study on the high-temperature deformation behavior of Ti-B25 titanium alloy, this simulation uses a specific constitutive equation (the specific formula is omitted here and displayed in the form of a picture), which accurately describes the rheological behavior of the material at different temperatures and strain rates.
3. Parameter setting
According to the thermal processing diagram of Ti-B25 titanium alloy, the deformation temperature is selected as 900℃ and the strain rate is 0.1 s^-1. At the same time, the friction coefficient between the billet and the die is set to 0.3 and the thermal conductivity is set to 5. The simulation process uses a step size of 0.5 mm, a total of 600 steps, and the data is saved every 2 steps to ensure the exhaustiveness of the simulation results.
II. Simulation results and analysis
1. Stress field analysis
Figure 3 shows the stress field distribution of Ti-B25 titanium alloy tube billets at different stages during the extrusion process. In the early stage, the large stress is concentrated at the head and tail of the tube; as the extrusion progresses, the stress increases significantly after the front end enters the extrusion barrel, and the stress is quickly released after passing through the sizing belt. The maximum equivalent stress continues to appear at the radius of the extrusion barrel die.
2. Strain field analysis
Figure 4 reveals the strain field changes during the extrusion process. The initial strain is small, and as the tube passes through the sizing belt, the strain increases sharply, especially at the radius of the sizing belt, which is easy to form a deformation dead zone, and special attention should be paid.
3. Temperature field analysis
Figure 5 shows the temperature field distribution during the extrusion process. In the early stage, the surface of the tube billet cools down due to heat exchange, and the deformation part heats up due to the conversion of plastic deformation work into heat energy, resulting in serious uneven temperature field. The highest and lowest temperature difference is 170℃, suggesting that the deformation temperature needs to be strictly controlled and the die design needs to be optimized.
III. Tube extrusion experiment
1. Surface quality evaluation
The experiment uses the parameters of deformation temperature 900℃, strain rate 0.1 s^-1, and extrusion speed 50 mm/s for extrusion. As shown in Figure 6, the extruded tube has high straightness and smooth surface, but there are slight flaws at the front end due to sudden temperature drop and unstable deformation, which is a normal phenomenon.
2. Room temperature mechanical properties
Through solid solution aging treatment, the Ti-B25 titanium alloy tube shows excellent strength-plasticity matching, meeting the strict requirements of ship antenna tubes. This result verifies the accuracy of numerical simulation and the rationality of process parameters.
