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Titanium alloy is widely applied in aerospace, medical, shipping and other fields due to its high specific strength and low density. The purpose of this study was to analyze the formability of Ti6Al4V alloys at elevated temperatures. An accurate constitutive model is the basic condition for accurately simulating the plastic forming of materials, and it is an important basis for optimizing the parameters of the hot forging forming process. In this study, the optimization algorithm was used to accurately identify the high-temperature constitutive model parameters of Ti6Al4V titanium alloy, and the hot working diagram was established to optimize the hot forming process parameters. The optimal forming conditions of Ti6Al4V titanium alloy are given. Ti6Al4V alloy was subjected to high-temperature compression tests at 800–1000 °C and at strain rates of 0.01–5 s−1 on a Gleeble-1500D thermal/mechanical simulation machine. Each parameter of the Hansel–Spittel constitutive model was taken as an independent variable, and the accumulated error between the stress calculated by the constitutive model and the stress obtained by experimentation was used as an objective function. Based on response surface methodology, an inverse optimization method for identifying the parameters of the high-temperature constitutive model of Ti6Al4V alloy is proposed in this paper. An orthogonal test design was adopted to obtain sample point data, and a third-order response surface approximate model was established. The genetic algorithm (GA) was applied to reversely optimize the parameters of the constitutive model. To verify the accuracy of the optimized constitutive model, the average absolute relative error (AARE) and correlation coefficient (R) were used to evaluate the reliability of optimized constitutive model. The R value of the model was 0.999, and the AARE value was 0.048, respectively, indicating that the established high-temperature constitutive model for Ti6Al4V alloy has good calculation accuracy. The flow stress behavior of the material could be accurately delineated. Meanwhile, in order to study the formability of Ti6Al4V alloy, the hot processing map of the alloy, based on a dynamic material model, was established in this paper. The optimum hot working domains of the Ti6Al4V alloy were determined within 840–920 °C/0.01–0.049 s−1 and 940–980 °C/0.11–1.65 s−1; the hot processing map was verified in combination with the microstructure, and the fine and equiaxed grains and a large amount of β phase could be found at 850 °C/0.01 s−1.

In the present work, the deformation behavior and processing maps of a low-carbon Fe-2 wt% Nb steel were studied by means of hot-compression tests at temperatures of 800–1150 °C and strain rates of 0.01–10 s−1. The hot-processing maps at different strains and corresponding microstructural evolution were constructed and discussed. The hot-deformation behaviors of two different phase regions, i.e., austenite + NbC dual-phase and ferrite + NbC dual-phase, were predicted by determining the constitutive equations using Arrhenius-type and Zener–Hollomon models. The results suggest that the hot-deformed microstructures of the material present a strong correlation with the processing parameters in the hot-processing maps. In addition, the optimum parameters based on the processing maps were obtained, and the instable and the safe domains during the hot deformation in the hot-processing maps provide solid theoretical guidance for industrial production.

The microstructure evolution and hot deformation behavior of 9Cr18Mo stainless bearing steel were studied with the hot compression test at the temperature ranging from 1 223 to 1 423 and strain rates from 0.01 to 10 s -1 . The results indicate that the 9Cr18Mo stainless steel shows strong positive strain rate sensitivity and negative temperature sensitivity. The softening mechanism is dynamic recrystallization and dynamic recovery mechanism. A constitutive equation with the strain compensation considered was developed and the prediction value is in good agreement with the experimental value. The processing map of 9Cr18Mo stainless steel was established with the Murty criteria. Combined with microstructure analysis, the optimal hot processing parameter range is between 1 050 ℃ and 1 120 ℃ and the strain rate is between 0.1 and 1 s -1 . The composition distribution of the microstructure of 9Cr18Mo stainless steel was analyzed with the EDS. In combination with the calculation results of the JMAPTPRO software, it was determined that the coarse banded carbides were not dissolved in the matrix at high temperature were composed of M 7 C 3 carbide and M 23 C 6 carbide. 利用热压缩试验研究了9Cr18Mo不锈轴承钢在变形温度为950~1 150 ℃、应变速率为0.01~10 s -1 条件下的显微组织演化和热变形行为。结果表明: 9Cr18Mo不锈钢表现出较强的正应变速率敏感性和负温度敏感性, 软化机制为动态再结晶和动态回复机制。建立了应变补偿型Arrhenius本构方程, 计算值与试验值吻合。基于Murty准则建立了9Cr18Mo不锈钢的热加工图, 结合显微组织分析, 确定了9Cr18Mo不锈钢的最佳加工参数为: 变形温度为1 050~1 120 ℃、应变速率为0.1~1 s -1 。采用EDS分析了9Cr18Mo不锈钢显微组织的成分分布, 结合JMAPTPRO软件计算结果, 确定了高温下未溶于基体的粗大带状碳化物由 M 7 C 3 型碳化物和 M 23 C 6 型碳化物组成。

To further investigate the properties of Incoloy825/P110 bimetallic composite seamless pipes, thermal deformation analysis was conducted on their billets. The thermal deformation and dynamic recrystallization (DRX) behavior of Incoloy825/P110 bimetallic composite materials were studied through hot compression tests at deformation temperatures (850–1150 °C) and strain rates (0.01–10 s −1 ). A constitutive relationship was established, and compensation and correction were made based on the differences in materials corresponding to different strain states. The hot processing map was established based on the thermal deformation behavior of bimetallic materials. In addition, the evolution of microstructure was also studied to verify the feasibility of the established hot processing map. The results show that the strain compensated Arrhenius can accurately predict the flow stress. By analyzing the microstructure using EBSD, it can be found that DRX behavior has a significant impact on the thermal processing properties of composite materials. This study provides an important theoretical basis for the production of Incoloy825/P110 bimetallic composite seamless pipes in the future.

The deteriorated plasticity arising from the insoluble precipitates may lead to cracks during the rolling of FeCrAl alloys. The microstructure evolution and hot deformation behavior of an FeCrAl alloy were investigated in the temperature range of 750–1200 °C and strain rate range of 0.01–10 s−1. The flow stress of the FeCrAl alloy decreased with an increasing deformation temperature and decreased strain rate during hot working. The thermal deformation activation energy was determined to be 329.49 kJ/mol based on the compression test. Then, the optimal hot working range was given based on the established hot processing maps. The hot processing map revealed four small instability zones. The optimal working range for the material was identified as follows: at a true strain of 0.69, the deformation temperature should be 1050–1200 °C, and the strain rate should be 0.01–0.4 s−1. The observation of key samples of thermally simulated compression showed that discontinuous dynamic recrystallization started to occur with the temperate above 1000 °C, leading to bended grain boundaries. When the temperature was increased to 1150 °C, the dynamic recrystallization resulted in a microstructure composed of fine and equiaxed grains.

In this study, a Zwick 1484 machine was employed to conduct hot compression experiments on a Mg-12Gd-3Y-0.6Zr alloy (GW123 magnesium alloy) at deformation temperatures ranging from 360 to 480 °C and strain rates from 10 −3 to 10 s −1 . A dataset comprising deformation temperature, strain, strain rate, and stress was built based on these experimental conditions, and the strain-compensated Arrhenius model and the backpropagation artificial neural network (BP-ANN) model were developed to investigate the hot deformation behavior of the GW123 magnesium alloy. The results show that the BP-ANN model has a correlation coefficient of 0.9986 and an average absolute error of 1.53, whereas the Arrhenius model has a correlation coefficient of 0.9729 and an average absolute error of 13. The reason for this result is that the BP-ANN model, by leveraging more data points (1500 in total) to optimize its adaptive parameters, can effectively capture complex nonlinear relationships between different deformation conditions simultaneously, thus providing superior accuracy in predicting the true stress–strain curve responses compared with the Arrhenius model. Furthermore, the optimal processing parameters for the GW123 magnesium alloy were determined through hot processing maps to be within the temperature range of 440–480 °C and strain rates of 10 −3  s −1 and 10 −2  s −1 .

A hot compression test was conducted across a range of temperatures (350, 400, 450, and 500 °C) and varying strain rates (0.001–10 s−1) to explore the hot compression behavior of the 6063 alloy. Hot processing maps were obtained based on the stress–strain curves. Optimal processing parameters were identified as residing within the intervals of (470–500 °C, 0.01–0.1108 s−1), achieving a maximum dissipation efficiency of 0.4, which is of great importance for perfecting hot processing. The microstructure evolution was characterized using an optical microscope and a transmission electron microscope. The initial grains were elongated under compressive deformation, and the density of dislocation rose with increasing strain rate and decreasing temperature. Dynamic recovery serves as the main dynamic softening mechanism during hot compression.

In this paper, a series of hot compression tests were carried out by using a Thermecamastor-Z thermomechanical simulator in the temperature range of 1020 ~ 1140 °C and a strain rate range of 0.01 ~ 1 s −1 . The microstructure evolution mechanism for the GH4742 nickel-based superalloy during hot compression was studied using electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) techniques. Constitutive models for the γ + γ' double-phase and γ single-phase regions are established. The hot deformation activation energies for γ + γ' double-phase and γ single-phase microstructures are determined to be 828.996 kJ/mol and 230.707 kJ/mol, respectively. Furthermore, the internal relationship between the flow stress, hot processing map, and dynamic recrystallization (DRX) mechanism is analyzed. The results show that the high Z value is mainly located in the instability region, and the DRX mechanism is dominated by discontinuous dynamic recrystallization (DDRX), supplemented by continuous dynamic recrystallization (CDRX), particle-stimulated nucleation (PSN), and the strong pinning of γ' precipitates, which delays the development of DRX. At moderate Z values, the DRX mechanism involves the combined effect of DDRX and weak CDRX, PSN, and γ' precipitate pinning, while at low Z values, the DRX mechanism mainly involves DDRX. The transition for the DRX mechanism is extremely sensitive to the Z value.

In order to accurately obtain the deformation characteristics and suitable thermal deformation conditions of TA15N titanium alloy and guide the design of deformation process parameters, a Gleeble 1500D was used to conduct hot compression tests on the thermal deformation behavior of a deformed TA15N titanium alloy under the condition of a strain rate of 0.01–10 s−1 and a deformation temperature of 850–1090 °C. The constitutive equations for the deformed TA15N titanium alloy based on the Arrhenius formula were developed, and the reliability of the constitutive equations was verified. A thermal processing map of the deformed TA15N titanium alloy was established by using the dynamic materials model (DMM). The research results show that the flow stress of the TA15N alloy decreased with an increase in deformation temperature and a decrease in strain rate. By utilizing electron backscattered diffraction (EBSD), the microstructural evolution and deformation process were analyzed. As the value of η decreased, dynamic recovery (DRV) gradually replaced dynamic recrystallization (DRX). This study supplies a relatively reliable processing interval for the new TA15N titanium alloy.

Multiple hot-compression tests were carried out on the 6082 aluminum (Al) alloy using a Gleeble-1500 thermal simulation testing machine. Data on flow stresses of the 6082 Al alloy at deformation temperatures of 623 to 773 K and strain rates from 0.01 to 5 s−1 were attained. Utilizing electron backscatter diffraction (EBSD) and a transmission electron microscope (TEM), the dynamic recrystallization behaviors of the 6082 Al alloy during hot compression in isothermal conditions were explored. With the test data, a hot-working processing map for the 6082 Al alloy (based on dynamic material modeling (DMM)) was drawn. Using the work-hardening rate, the initial critical strain causing dynamic recrystallization was determined, and an equation for the critical strain was constructed. A dynamic model for the dynamic recrystallization of the 6082 Al alloy was established using analyses and test results from the EBSD. The results showed that the safe processing zone (with a high efficiency of power dissipation) mainly corresponded to a zone with deformation temperatures of 703 to 763 K and strain rates of 0.1 to 0.3 s−1. The alloy was mainly subjected to continuous dynamic recrystallization in the formation of the zone. According to the hot-working processing map and an analysis of the microstructures, it is advised that the following technological parameters be selected for the 6082 Al alloy during hot-forming: a range of temperatures between 713 and 753 K and strain rates between 0.1 and 0.2 s−1.