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In this study, hot compression experiments were conducted on cast TC21 titanium alloy using a Gleeble-1500D thermal simulation compression tester, and the hot-compressed specimens were heat-treated. The data obtained after analyzing the thermal compression of cast TC21 titanium alloy were analyzed to construct a thermal machining diagram with a strain of 0.8 and to optimize the machining window. This study investigated the microstructure of the alloy after hot pressing experiments and heat treatment, applying the study of the microstructure evolution law of cast TC21 titanium alloy. The analysis of the tissue evolution law established the dynamic and static recrystallization volume fraction as a function of heat deformation parameters. The results show that the optimal processing window for cast TC21 titanium alloy is a deformation temperature in the range of 1373 K–1423 K and a strain rate of 0.1 s−1. The increase in deformation volume and deformation temperature both favor recrystallization and make the recrystallization volume fraction increase, but the increase in strain rate will inhibit the increase in the recrystallization degree to some extent. The dynamic and static recrystallization equations for the cast TC21 titanium alloy at different temperatures were constructed. The experimental measurements of recrystallization volume fraction are in good agreement with the predicted values.

High-temperature plastic deformation is one of the main methods for the fabrication of titanium-based alloys. Accurate determination of the mechanical constitutive relation is pivotal for the design, optimization, as well as the prediction of the mechanical behavior of materials. In this study, finite element simulations were carried out to simulate the Gleeble thermal compression experiment of titanium alloy samples, focusing on different thermocouple design parameters, including thermocouple material and wire diameter, etc. The results show that the heat dissipation of the thermocouple distorted the local temperature field of the contact point between the sample and the thermocouple, resulting in a deviation of the measured temperature. Through finite element method (FEM) simulation and analysis of the changes caused by various factors and comparison with the metallographic morphology of titanium alloy samples from relevant heat treatment experiments, it was shown that the material and wire diameter of the thermocouple, the thermal conductivity coefficient of sample, and the testing temperature of the sample all affected the measurement results. The thermal conductivity of sample had the largest influence on the measurement accuracy. Based on the finite element simulation and experimental comparison, the corresponding correction method and correction formula are proposed.

The Gleeble-3800 thermal simulation machine was used to perform hot compression experiments on a new type of β alloy, Ti-6Mo-5V-3Al-2Fe (wt.%), at temperatures of 700–900 °C, strain rates of 5 × 10−1 to 5 × 10−4 s−1, and total strain of 0.7. Transmission and EBSD techniques were used to observe the microstructure. The results show that the deformation activation energy of the alloy was 356.719 KJ/mol, and dynamic recrystallization occurred during the hot deformation. The higher the deformation temperature was, the more obvious the dislocations that occurred and the more sufficient the dynamic recrystallization that occurred, but the effect of strain rate was the opposite. When the deformation temperature was higher than the phase transition point, the recrystallized grains clearly grew up. The calculated strain rate sensitivity index of the alloy was 0.14–0.29. The constitutive equation of hot deformation of Ti-6Mo-5V-3Al-2Fe alloy was established by using the Arrhenius hyperbolic sine equation. The dynamic DMM hot working diagram with the strain of 0.7 was constructed. The relatively good hot working area of the alloy was determined to be the deformation temperature of 700–720 °C and 0.0041–0.0005 s−1.

2219 aluminum alloy is a kind of high-strength Al-Cu-Mn alloy that can be strengthened by heat treatment. Its mechanical property parameters and forming properties are greatly affected by the deformation rate, temperature and strain. Taking 2219 aluminum alloy extruded bar as the research object, the Gleeble-3500 thermomechanical simulator was used to analyze the thermal compression deformation behavior of 2219 aluminum alloy under different temperatures and strain rates. The results show that the deformation behavior of 2219 aluminum alloy under high temperatures is greatly influenced by the deformation temperature and strain rate, and the flow stress is the result of high-temperature softening, strain hardening and deformation rate hardening. According to the experiment results, the Arrhenius constitutive model and the exponential constitutive model considering the influence of temperature and strain rate, respectively, were established, and the predicted results of the two constitutive models were in good agreement with the test results. On this basis, the processing map of 2219 aluminum alloy was established. Under the same strain rate condition with an increase of the deformation temperature, the power dissipation efficiency increases gradually, and the driving force of 2219 aluminum alloy to change its microstructure increases gradually. At the same deformation temperature, the lower the strain rate, the less possibility of plastic instability.

In this work, hot compression experiments of 300M steel were performed at 900−1150 °C and 0.01−10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.