35% SiC_p/2024A1复合材料的热变形行为(英文)

采用Gleeble-1500D热模拟试验机,对35%SiCp/2024A1复合材料在温度350~500°C、应变速率0.01~10s-1的条件下进行热压缩试验,研究该复合材料的热变形行为与热加工特征,建立热变形本构方程和加工图。结果表明,35%SiCp/2024A1复合材料的流变应力随着温度的升高而降低,随着应变速率的增大而升高,说明该复合材料是正应变速率敏感材料,其热压缩变形时的流变应力可采用Zener-Hollomon参数的双曲正弦形式来描述;在本实验条件下平均热变形激活能为225.4 kJ/mol。为了证实其潜在的可加工性,对加工图中的稳定区和失稳区进行标识,并通过微观组织得到验证。综合考虑热加工图和显微组织,得到变形温度500°C、应变速率0.1~1 s-1是复合材料适宜的热变形条件。     

High temperature deformation and processing map of a NiTi intermetallic alloy

The deformation behavior of a 49.8 Ni-50.2 Ti (at pct) alloy was investigated using the hot compression test in the temperature range of 700 °C–1100 °C, and strain rate of 0.001 s^?1 to 1 s^?1. The hot tensile test of the alloy was also considered to assist explaining the related deformation mechanism within the same temperature range and the strain rate of 0.1 s^?1. The processing map of the alloy was developed to evaluate the efficiency of hot deformation and to identify the instability regions of the flow. The peak efficiency of 24–28% was achieved at temperature range of 900 °C–1000 °C, and strain rates higher than 0.01 s^?1 in the processing map. The hot ductility and the deformation efficiency of the alloy exhibit almost similar variation with temperature, showing maximum at temperature range of 900 °C–1000 °C and minimum at 700 °C and 1100 °C. Besides, the minimum hot ductility lies in the instability regions of the processing map. The peak efficiency of 28% and microstructural analysis suggests that dynamic recovery (DRV) can occur during hot working of the alloy. At strain rates higher than 0.1 s^?1, the peak efficiency domain shifts from the temperature range of 850 °C–1000 °C to lower temperature range of 800 °C–950 °C which is desirable for hot working of the NiTi alloy. The regions of flow instability have been observed at high Z values and at low temperature of 700 °C and low strain rate of 0.001 s^?1. Further instability region has been found at temperature of 1000 °C and strain rates higher than 1 s^?1 and at temperature of 1100 °C and all range of strain rates.     

Characterization of hot deformation and microstructure evolution of a new metastable β titanium alloy

The hot deformation characteristics of as-forged Ti?3.5Al?5Mo?6V?3Cr?2Sn?0.5Fe?0.1B?0.1C alloy within a temperature range from 750 to 910 °C and a strain rate range from 0.001 to 1 s^?1 were investigated by hot compression tests. The stress?strain curves show that the flow stress decreases with the increase of temperature and the decrease of strain rate. The microstructure is sensitive to deformation parameters. The dynamic recrystallization (DRX) grains appear while the temperature reaches 790 °C at a constant strain rate of 0.001 s^?1 and strain rate is not higher than 0.1 s^?1 at a constant temperature of 910 °C. The work-hardening rate θ is calculated and it is found that DRX prefers to happen at high temperature and low strain rate. The constitutive equation and processing map were obtained. The average activation energy of the alloy is 242.78 kJ/mol and there are few unstable regions on the processing map, which indicates excellent hot workability. At the strain rate of 0.1 s^?1, the stress?strain curves show an abnormal shape where there are two stress peaks simultaneously. This can be attributed to the alternation of hardening effect, which results from the continuous dynamic recrystallization (CDRX) and the rotation of DRX grains, and dynamic softening mechanism.     

Hot deformation behavior of Al–9.0Mg–0.5Mn–0.1Ti alloy based on processing maps

Hot deformation behavior of extrusion preform of the spray-formed Al–9.0Mg–0.5Mn–0.1Ti alloy was studied using hot compression tests over deformation temperature range of 300–450 °C and strain rate range of 0.01–10 s^?1. On the basis of experiments and dynamic material model, 2D processing maps and 3D power dissipation maps were developed for identification of exact instability regions and optimization of hot processing parameters. The experimental results indicated that the efficiency factor of energy dissipate (η) lowered to the minimum value when the deformation conditions located at the strain of 0.4, temperature of 300 °C and strain rate of 1 s^?1. The softening mechanism was dynamic recovery, the grain shape was mainly flat, and the portion of high angle grain boundary (>15°) was 34%. While increasing the deformation temperature to 400 °C and decreasing the strain rate to 0.1 s^?1, a maximum value of η was obtained. It can be found that the main softening mechanism was dynamic recrystallization, the structures were completely recrystallized, and the portion of high angle grain boundary accounted for 86.5%. According to 2D processing maps and 3D power dissipation maps, the optimum processing conditions for the extrusion preform of the spray-formed Al–9.0Mg–0.5Mn–0.1Ti alloy were in the deformation temperature range of 340–450 °C and the strain rate range of 0.01–0.1 s^?1 with the power dissipation efficiency range of 38%–43%.     

Constitutive behavior,microstructural evolution and processing map of extruded Al–1.1Mn–0.3Mg–0.25RE alloy during hot compression

Hot compression tests of an extruded Al–1.1Mn–0.3Mg–0.25RE alloy were performed on Gleeble–1500 system in the temperature range of 300–500 °C and strain rate range of 0.01–10 s^?1. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener–Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al–1.1Mn–0.3Mg–0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440–450 °C and strain rate of 0.01 s^?1.     

Characterization of hot deformation behavior of Haynes230 by using processing maps

The hot deformation characteristics of Haynes230 has been investigated in the temperature range 1050–1250 °C and strain rate range 0.001–10 s^?1 using hot compression tests. Power dissipation map for hot working are developed on the basis of the Dynamic Materials Model. The map exhibits two domains of dynamic recrystallization (DRX): one occurring in the temperature range of 1200–1250 °C and in the strain rate range of 0.001–0.03 s^?1, which associated with grain coarsening; the other occurring in the temperature range of 1100–1200 °C and strain rate range of 0.001–0.01 s^?1, which are the optimum condition for hot working of this material. The average apparent activation energy for hot deformation is calculated to be 449 kJ/mol. The material undergoes flow instabilities at temperatures of 1050–1100 °C and at strain rates of 1–10 s^?1, as predicted by the continuum instability criterion. The manifestations of the instabilities have been observed to be adiabatic shear bands which are confirmed by optical observation.     

Flow curve correction and processing map of 2050 Al–Li alloy

Hot compression tests of 2050 Al–Li alloy were performed in the deformation temperature range of 340–500 °C and strain rate range of 0.001–10 s^–1 to investigate the hot deformation behavior of the alloy. The effects of friction and temperature difference on flow stress were analyzed and the flow curves were corrected. Based on the dynamic material model, processing map at a strain of 0.5 was established. The grain structure of the compressed samples was observed using optical microscopy. The results show that friction and temperature variation during the hot compression have significant influences on flow stress. The optimum processing domains are in the temperature range from 370 to 430 °C with the strain rate range from 0.01 to 0.001 s^–1, and in the temperature range from 440 to 500 °C with the strain rate range from 0.3 to 0.01 s^–1; the flow instable region is located at high strain rates (3–10 s^–1) in the entire temperature range. Dynamic recovery (DRV) and dynamic recrystallization (DRX) are the main deformation mechanisms of the 2050 alloy in the stable domains, whereas the alloy exhibits flow localization in the instable region.     

Deformation behavior and processing maps of Mg-Zn-Y alloy containing I phase at elevated temperatures

The microstructure and mechanical properties of extruded Mg-Zn alloy containing Y element were investigated in temperature range of 300–450 °C and strain rate range of 0.001–1 s^?1 through hot compression tests. Processing maps were used to indicate optimum conditions and instability zones for hot deformation of alloys. For Mg-Zn and Mg-Zn-Y alloys, peak stress, temperature and strain rate were related by hyperbolic sine function, and activation energies were obtained to be 177 and 236 kJ/mol, respectively. Flow curves showed that the addition of Y element led to increase in peak stress and decrease in peak strain, and indicated that DRX started at lower strains in Mg-Zn-Y alloy than in Mg-Zn alloy. The stability domains of Mg-Zn-Y alloy were indicated in two domains as 1) 300 °C, 0.001 s^?1; 350 °C, 0.01–0.1 s^?1 and 400 °C, 0.01 s^?1 and 2) 450 °C, 0.01–0.1 s^?1. Microstructural observations showed that DRX was the main restoration mechanism for alloys, and fully dynamic recrystallization of Mg-Zn-Y alloy was observed at 450 °C. The instability domain in Mg-Zn-Y alloy was located significantly at high strain rates. In addition, the instability zone width of Mg-Zn and Mg-Zn-Y alloys increased with increasing strain, and cracks, twins and severe deformation were considered in these regions.     

Cu-Ni-Si-P合金热变形行为及热加工图

采用高温等温压缩试验,对Cu?Ni?Si?P合金在应变速率0.01~5?1、变形温度600~800°C条件下的高温变形行为进行了研究,得出了该合金热压缩变形时的热变形激活能Q和本构方程。根据实验数据与热加工工艺参数构建了该合金的热加工图,利用热加工图对该合金在热变形过程中的热变形工艺参数进行了优化,并利用热加工图分析了该合金的高温组织变化。热变形过程中Cu?Ni?Si?P合金的流变应力随着变形温度的升高而降低,随着应变速率的提高而增大,该合金的动态再结晶温度为700°C。该合金热变形过程中的热变形激活能Q为485.6 kJ/mol。通过分析合金在应变为0.3和0.5时的热加工图得出该合金的安全加工区域的温度为750~800°C,应变速率为0.01~0.1 s?1。通过合金热变形过程中高温显微组织的观察,其组织规律很好地符合热加工图所预测的组织规律。     

Thermomechanical Characterization of Mg-9Al-1Zn Alloy Using Power Dissipation Maps

A processing map is developed on the basis of the Dynamic Material Model for Mg-9Al-1Zn. The model considers the work piece as a dissipator of power and power loss variation with temperature and strain rate constitutes the power dissipation map. To this end, the thermomechanical (i.e., hot compression) characteristics of a Mg-9Al-1Zn alloy was studied in the temperature range of 250-425 °C and strain rates of 0.001-1 s^?1. The strain rate sensitivity (m), power dissipation efficiency (η), and instability parameter (ξ) are computed based on the experimental hot compression data. The deformation mechanisms of different regions in the maps are analyzed and corresponding microstructures are investigated. The processing map of Mg-9Al-1Zn alloy exhibits five workability domains. Dynamic recrystallization (DRX) was observed in three of the domains, while in the two other domains grain boundary sliding, twining, and precipitation are the dominant mechanisms. The optimum hot working conditions of Mg-9Al-1Zn alloy are located in the two domains where DRX takes place. They correspond to 375 °C/0.001 s^?1 and 380 °C/1 s^?1 with peak efficiency of 42 and 36%, respectively.     

Optimization of Hot Extrusion Process Parameters of Mg97Y2Zn1 Alloy Based on the Processing Maps

The processing maps of the Mg₉₇Y₂Zn₁ alloy have been developed for optimizing hot workability and controlling the microstructure in this paper. Compression tests were conducted in the temperature range from 250 to 450 °C and the strain rate range from 0.001 to 5.0 s^?1. The processing maps were calculated based on the flow stress behavior and analyzed according to the dynamic materials model. The maps exhibited a stability domain that occurs in the temperature of 430-450 °C for a strain rate of 0.002-0.003 s^?1 and having a maximum efficiency of 50%. A hot extrusion test was carried out to assess the prediction of the processing maps for Mg₉₇Y₂Zn₁ alloy. The influence of the extrusion temperature on the microstructure and tensile properties of the extruded alloys was analyzed to identify the optimum processing parameters. The results have shown good agreement between the regimes exhibited by the map and the microstructure of the extruded alloy.     

Hot deformation behavior of novel imitation-gold copper alloy

The hot deformation behavior of a novel imitation-gold copper alloy was investigated with Gleeble–1500 thermo-mechanical simulator in the temperature range of 650–770 °C and strain rate range of 0.001–1.0 s^?1. The hot deformation constitutive equation was established and the thermal activation energy was obtained to be 249.60 kJ/mol. The processing map at a strain of 1.2 was developed. And there are two optimal regions in processing map, namely 650–680 °C, 0.001–0.01 s^?1 and 740–770 °C, 0.01–0.1 s^?1. Optical microscopy was employed to investigate the microstructure evolution of the alloy in the process of deformation. Recrystallized grains and twin crystals were found in microstructures of the hot deformed alloy.     

Thermomechanical characterization of β-stabilized Ti–45Al–7Nb–0.4W–0.15B alloy

The correlation between hot deformation parameters and the workability of β-stabilized Ti–45Al–7Nb–0.4W–0.15B (at. %) alloy was studied in the temperature range 1000–1200 °C and the strain rate range 0.001–1 s^?1. Deformation mechanisms were characterized by detailed analyses of the deformation behavior and microstructural observations. The results indicate that the deformation and recrystallization occurred preferentially in the grain boundary β phases because its good high temperature deformability enhances grain boundary sliding and migration, and thus improves the workability. Decomposition of the β phase to α₂ and γ phases partly accommodates the stress concentration and is thus beneficial in hot deformation. Appropriate deformation processing parameters were suggested based on the processing map, and were successfully applied in the quasi-isothermal canned forging of industrial-scale billets.     

Isothermal compression behavior and constitutive modeling of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

Hot compression behavior of Ti-5Al-5Mo-5V-1Cr-1Fe alloy with an equiaxed (α+β) starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain–stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800–840 °C with a strain rate of 10 s^?1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^?1 in the temperature range of 860–900 °C. The processing map analysis shows that hot working of Ti-5Al-5Mo-5V-1Cr-1Fe alloy should be conducted with the strain rate lower than 0.01 s^?1 to extend its workability.     

Effect of strain rate on hot deformation characteristics of GH690 superalloy

In order to clarify the effect of strain rate on hot deformation characteristics of GH690 superalloy, the hot deformation behavior of this superalloy was investigated by isothermal compression in the temperature range of 1000–1200 °C and strain rate range of 0.001–10 s^?1 on a Gleeble–3800 thermo-mechanical simulator. The results reveal that the flow stress is sensitive to the strain rate, and the dynamic recrystallization (DRX) is the principal softening mechanism. The strain rate of 0.1 s^?1 is considered to be the critical point during the hot deformation at 1000 °C. The DRX process is closely related to the strain rate due to the adiabatic temperature rise. The strain rate has an important influence on DDRX and CDRX during hot deformation. The nucleation of DRX can be activated by twin boundaries, and there is a lower fraction of ∑ 3ⁿ (n=1, 2, 3) boundaries at the intermediate strain rate of 0.1 s^?1.     

Research on the Hot Deformation Behavior of Al-Zn-Mg-Sc-Zr Alloy During Compression at Elevated Temperature

The flow behavior of Al-Zn-Mg-Sc-Zr alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermo-mechanical equipment. Compression tests were performed in the temperature range of 340-500 °C and in the strain rate range of 0.001-10 s^?1.The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature, and decreases with increasing temperature at a given imposed strain rate. The relationship between flow stress and strain rate and temperature was derived by analyzing the experimental data. The constitutive equation of Al-Zn-Mg-Sc-Zr alloy during hot compression deformation can be described by the Arrhenius relationship of the hyperbolic sine form. The values of A, n, and α in the analytical expression of strain rate are fitted to be 1.49 × 10¹⁰ s^?1, 7.504, and 0.0114 MPa^?1, respectively. The hot deformation activation energy of the alloy during compression is 150.25 kJ/mol. The temperature and strain rate have great influences on microstructure evolution of Al-Zn-Mg-Sc-Zr alloy during hot compression deformation. According to microstructure evolution, the dynamic flow softening is mainly caused by dynamic recovery and dynamic recrystallization in this present experiment.     

Microstructure evolution and hot deformation behavior of Cu−3Ti−0.1Zr alloy with ultra-high strength

The hot compression deformation behavior of Cu–3Ti–0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble–3500 thermal-mechanical simulator at temperatures from 700 to 850 °C with the strain rates between 0.001 and 1 s⁻¹. The results show that work hardening, dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation. The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol. The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result, and the hot processing maps are established based on the dynamic material model. The optimal hot deformation temperature range is between 775 and 850 °C and the strain rate range is between 0.001 and 0.01 s⁻¹.     

Constitutive Modeling of Dynamic Recrystallization Behavior and Processing Map of 38MnVS6 Non-Quenched Steel

The dynamic recrystallization behavior of 38MnVS6 non-quenched steel was investigated by hot compression tests on a Gleeble1500 thermomechanical simulator. True stress-strain curves and deformed specimens were obtained in the temperature range of 850-1200 °C and the strain rate range of 0.01-10 s^?1. By regression analysis of the experimental results, the critical strain model and austenite grain size model for dynamic recrystallization were established as a function of Zener-Hollomon parameter. The dynamic recrystallization kinetic model for 38MnVS6 non-quenched steel was established on the basis of the modified Avrami equation. In addition, based on the dynamic material model, the processing map of the steel was established at the strain of 0.5. It was found that the unstable phenomena of the steel did not appear at the deformation conditions. The processing map exhibited a domain of complete dynamic recrystallization occurring in the temperature range of 950-1200 °C and the strain rate range of 0.01-5 s^?1, which were the optimum parameters for the hot working of the steel.     

Microstructure and hot deformation behavior of A356/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite fabricated by infiltration method

The hot deformation behavior of an A356/Al₂O₃ composite fabricated by the infiltration method was characterized in the temperature range of 300-500 °C and strain rate range of 0.001-1/s using compressive tests. The composite consists of an Al-Si based matrix and nano-sized Al₂O₃ particulates. A constitutive model was established based on the hyperbolic sine Arrhenius type equation and its hot workability was evaluated by means of processing maps based on Dynamic Material Modeling. The activation energy for hot deformation was calculated to be 223 kJ/mol, which is higher than the activation energy for self-diffusion of pure aluminum (142 kJ/mol). The optimum processing condition for the hot working of the composite was found to exist at 500 °C with a strain rate of 1/s, where a dynamic recrystallized microstructure was observed and the maximum efficiency was exhibited in the processing map. Voids were frequently detected at 500 °C with lower strain rates, deteriorating the workability of the composite.     

新型无镍白色铜合金的热加工图及其热变形机制(英文)

采用Gleeble-1500热模拟实验机在温度为600~800°C、应变速率为0.01~10 s-1的热变形条件下对新型无镍白色Cu-12Mn-15Zn-1.5Al-0.3Ti-0.14B-0.1Ce(质量分数,%)合金进行热压缩模拟实验;根据该合金热变形行为及热加工特征,建立该合金热变形的本构方程和热加工图。该合金热变形过程中变形激活能为203.005 k J/mol。当真应变为0.7时,合金热加工图中存在一个失稳区,此区域的变形温度为600~700°C,应变速率为0.32~10 s-1。在较适宜的热变形条件(800°C、10 s-1)下获得的合金具有良好的表面质量和内部组织。同时,该无镍合金具有与传统镍白铜Cu-15Ni-24Zn-1.5Pb合金相近似的白色色度和肉眼不易察觉的色差(小于1.5)。