Based on the indirect hot-stamping test system, the effect of pre-forming on the microstructure evolution (grain size, dislocation density, martensite phase transformation) and mechanical properties of the blank in indirect hot stamping is systematically studied using ultra-high-strength steel 22MnB5. It is found that the average austenite grain size slightly decreases with the increase in pre-forming. After quenching, the martensite also becomes finer and more uniformly distributed. Although the dislocation density after quenching slightly decreases with the increase in pre-forming, the overall mechanical properties of the quenched blank are not greatly affected by pre-forming under the combined effect of the grain size and dislocation density. Then, this paper discusses the effect of the pre-forming volume on part formability in indirect hot stamping by manufacturing a typical beam part. According to the numerical simulations and experimental results, when the pre-forming volume increases from 30% to 90%, the maximum thickness thinning rate of the beam part decreases from 30.1% to 19.1%, and the final beam part has better formability and more uniform thickness distribution results when the pre-forming volume is 90%.

Aluminum alloy has been used as the skin material for rail vehicles and automobiles to meet the requirements of environmental protection. The hot stamping-in-die quenching composite forming (HFQ) process is a promising technology to compensate for the poor formability of the aluminum alloy sheet at room temperature. In this paper, the high-temperature mechanical properties of 5083 aluminum alloy under various temperature (200 °C, 300 °C, 400 °C, 450 °C) and strain rate conditions (0.01 s⁻¹, 0.10 s⁻¹, 1.00 s⁻¹) were investigated by uniaxial tensile tests. The finite element software of PAM-STAMP was employed to simulate the forming process of high-speed train skin. The effects of forming method and process parameters on the minimum thickness and springback of the skin were analyzed using the Response Surface Methodology (RSM). After parameter optimization, the forming experiment verified the simulation results and the test part met the quality requirements: the thickness above 3.84 mm and the springback within 1.1 mm. Mechanical properties of the sheet before and after HFQ were examined by uniaxial tensile tests at room temperature. It can be inferred from the comparison that the yield strength of the Al5083 sheet increases, but the elongation decreases from the HFQ process.

Through the study of the thermal rheological behavior of Ti6Al4V alloy at different temperatures (500 °C, 600 °C, 700 °C, and 800 °C) and different strain rates (0.1 s⁻¹, 0.05 s⁻¹, 0.01 s⁻¹, and 0.005 s⁻¹), a constitutive model was developed for Ti6Al4V alloy across a wide temperature range in the hot stamping process. The model’s correlation coefficient reached 0.9847, indicating its high predictive accuracy. Hot processing maps suitable for the hot stamping process of Ti6Al4V alloy were developed, demonstrating the significant impact of the strain rate on the hot formability of Ti6Al4V alloy. At higher strain rates (>0.05 s⁻¹), the hot processing of Ti6Al4V alloy is less prone to instability. Combining hot processing maps with hot stamping experiments, it was found that the forming quality and thickness uniformity of parts improved significantly with the increase in stamping speed. The phase composition and microstructures of the forming parts under different heating temperature conditions have been investigated using SEM, EBSD, XRD, and TEM, and the maximum heating temperature of hot stamping forming was determined to be 875 °C. The recrystallization mechanism in hot stamping of Ti6Al4V alloys was proposed based on EBSD tests on different sections of a hot stamping formed box-shaped component. With increasing deformation, the effect of dynamic recrystallization (DRX) was enhanced. When the thinning rate reached 15%, DRX surpassed dynamic recovery (DRV) as the dominant softening mechanism. DRX grains at different thinning rates were formed through both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), with CDRX always being the dominant mechanism.

Titanium alloy hot stamping technology has a wide range of application prospects in the field of titanium alloy part processing due to its high production efficiency and low manufacturing cost. However, the challenges of forming titanium alloy parts with large depths and deformations have restricted its development. In this study, the hot stamping process of a Ti6Al4V alloy box-shaped part was investigated using ABAQUS 2020 software. The thermodynamic properties of a Ti6Al4V alloy sheet were explored at different temperatures (400 °C, 500 °C, 600 °C, 700 °C, 800 °C) and different strain rates (0.1 s⁻¹, 0.05 s⁻¹, 0.01 s⁻¹). In addition, the influence law of hot stamping process parameters on the minimum thickness of the formed part was revealed through the analysis of response surface methodology (RSM), ultimately obtaining the optimal combination of process parameters for Ti6Al4V alloy hot stamping. The experimental results of the hot stamping process exhibited a favorable correlation with the simulated outcomes, confirming the accuracy of the numerical simulation. The study on the microstructure evolution of the formed parts showed that grain refinement strengthening occurred in the part with large deformation, and the formed box-shaped parts exhibited a uniform and fine microstructure overall, demonstrating high forming quality. The achievements of the work provide important guidance for the fabrication of titanium alloy parts with large depths and deformations used in heavy industrial production.

With the vigorous development of rail transit trains around the world and the emergence of global environmental pollution and energy shortages, the world has an urgent need for manufacturing technology for lightweight aluminum alloy rail transit train components. This paper mainly studied the superplastic forming law of 5083Al for rail transit. Through the high-temperature tensile test and blowing forming experiments, the superplastic properties of 5083Al were determined. Based on this, the die design, finite element simulation, and forming experiment of the rail vehicle side window were carried out. In order to study the superplastic deformation behavior of industrial 5083Al under complex stress conditions, the influence of the depth, area ratio, and friction coefficient of the pre-forming die on the part thickness distribution is simulated. The side window is made of a high-strength 5083Al sheet in the form of bending at both ends to ensure the strength of the connection between the overall side window and the side wall skeleton. The variation law of the side wall forming height of 5083Al box-shaped parts was studied. The efficient manufacture of parts that meet quality standards was made possible by the optimization of the pressure profile. The microstructure changes of the material after superplastic forming were studied by Energy Dispersive Spectrometer (EDS) and Electron Backscattered Diffraction (EBSD).