Hot Deformation Behavior and Processing Map of SiCp/2024Al Composite

采用Gleeble-1500D热模拟试验机,对30%SiCp/2024A1复合材料在温度为350~500℃、应变速率为0.01~10 s-1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,30%SiCp/2024A1复合材料的流变应力随温度升高而降低,随应变速率增大而升高,说明该复合材料是一个正应变速率敏感的材料,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Q为153.251 k J/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结构,变形温度为450℃,应变速率为1 s-1是复合材料适宜的热变形条件。     

35%SiCp/Al复合材料的热加工图及变形组织

利用Gleeble-1500D热模拟试验机对35%SiCp/Al复合材料进行压缩试验,研究其在温度为350～500℃、应变速率为0.01～10 s~(-1)条件下的高温塑性变形行为。由试验得出的变形过程中的应力-应变曲线,建立了功率耗散效率图和热加工图,确定了热加工的稳定区和失稳区,观察分析了加工图中不同区域的显微组织。结果表明:35%SiCp/Al复合材料的流变应力随变形温度的降低或应变速率的升高而增加,应力-应变曲线变化主要以动态再结晶为特征。最适合热变形加工的条件是变形温度为370～420℃、应变速率为0.15～1 s~(-1)的区域,加工安全区微观组织明显改善,并出现再结晶晶粒。     

片状粉末冶金Al_2O_3/Al复合材料的热变形及加工图（英文）

采用Gleeble-1500D热模拟试验机在300~450°C、0.001~1.0 s-1条件下对不同铝片层厚度的Al2O3/Al复合材料进行变形行为研究。实验结果表明,在设定的温度下,流变应力随着应变速率的增加而增加,而在设定的应变速率下,流变应力随着温度的升高而降低。在所采用的实验条件下,片层Al2O3/Al复合材料的高温流变行为可以用双曲正弦函数来描述。Al2O3/Al-2μm和Al2O3/Al-1μm复合材料在进行真应变为0.6的热变形时最优加工工艺参数分别为300~330°C,0.007~0.03 s-1和335~360°C,0.015~0.06 s-1。而热加工图也明确了此两种复合材料的流变失稳区。     

中体分SiC_p/A1复合材料的热变形行为和功率耗散图

采用Gleeble-1500热模拟试验机对30%SiCP/2024A1复合材料在温度为623~773 K、应变速率为0.01~10 s-1变形条件下热变形流变行为进行了研究。由试验得出变形过程中的真应力真应变曲线,建立热变形本构方程和功率耗散图。结果表明,复合材料的流变应力随温度的升高而降低,随应变速率的增大而升高,说明该复合材料是一个正应变速率敏感的材料。该复合材料热压缩变形时的流变应力行为可采用Zener-Hollomon参数的双曲正弦形式来描述,热变形激活能Q为571.377 kJ/mol。高温高应变速率条件下的功率耗散系数大,该变形区发生了组织转变。     

高钛6061铝合金的热变形行为（英文）

利用应力应变曲线、热加工图,结合电子透射电子显微镜和背散射衍射技术研究在变形温度为350~510°C、应变速率为0.001~10 s-1时高钛6061铝合金的热变形行为。结果表明,该合金的热压缩变形流变峰值应力随变形温度的升高和应变速率的降低而降低;在实验参数范围内平均热变形激活能为185 k J/mol;建立了流变应力模型;该合金热变形时主要的软化机制为动态回复;根据材料动态模型获得了高钛6061铝合金的热加工图,最佳的热加工窗口温度为400~440°C,应变速率为0.001~0.1 s~(-1)。     

非真空熔铸Cu-Cr-Zr合金的热变形行为及加工图

利用Gleeble-1500热模拟实验机对非真空熔铸Cu-0.94Cr-0.34Zr合金进行高温热压缩变形,研究在变形温度为500～800℃、应变速率为0.01 ～1 s-1工作条件下该合金的流变应力行为,建立合金热变形流变应力本构方程及加工图.结果表明:流变应力随变形温度的升高而降低,随应变速率的降低而减小;可用包含Zener-Hollomon参数的Arrhenius双曲正弦关系式描述Cu-0.94Cr-0.34Zr合金的热变形行为,建立本构方程,算出其激活能为418.35 kJ/mol.依据动态材料模型,建立热加工图,确定热变形失稳区和安全热加工区域,合金最佳热加工条件为:变形温度775℃,应变速率0.01s-1.     

钨含量对W-Cu复合材料高温变形行为的影响

采用Gleeble-1500D热模拟试验机,在温度为650~950℃、应变速率为0.01~5 s-1、总应变量为0.7的条件下,对25%W-Cu和50%W-Cu(质量分数)复合材料的热变形行为及其热加工图进行研究和分析。结果表明:此两种复合材料的高温流动应力—应变曲线主要以动态再结晶为特征,峰值应力随变形温度的降低或应变速率的升高而增大;在真应力—应变曲线基础上建立的W-Cu复合材料高温变形本构模型较好地表征了其高温流变特性;同时,利用50%W-Cu复合材料DMM加工图分析了其变形机制和失稳机制,确定其热加工工艺参数应优先选择变形温度为650~700℃、应变速率为1~5 s-1,或者变形温度为850~950℃、应变速率为0.01~0.1 s-1。     

铸态27SiMn钢热变形行为及热加工图

利用Gleeble-1500D热模拟试验机,在应变速率为0.01~10 s-1,变形温度为1000~1150℃条件下对铸态27Si Mn钢进行等温恒应变速率压缩试验。通过真应力-真应变曲线,分析了应变速率和变形温度对流变应力的影响规律,建立了铸态27Si Mn钢热变形时的本构方程和热加工图。结果表明,铸态27Si Mn钢高温变形时的峰值应力随应变速率的增大和变形温度的降低而升高;变形激活能为Q=369.0 k J/mol;热变形失稳区域集中在变形温度1000~1060℃、应变速率为1~10 s-1的区域内;最优热加工条件为变形温度1130~1150℃,应变速率4~10 s-1的区域,此时表现为典型的动态再结晶,对应的峰值效率达到35%。     

GH3535合金的热变形和热加工图(英文)

通过热压缩实验研究GH3535合金在温度区间1000~1200°C和应变速率区间0.01~50 s-1的热变形行为。在实验数据基础上得到合金应力曲线和热加工图,且其激活能为356.3 k J/mol。热加工图分为2个区域,稳定区域发生在所有温度区间和应变速率区间0.01~1 s-1,失稳区域发生在应变速率区间1~50 s-1。显微组织观察表明,完全动态再结晶发生条件为(1150°C,0.01 s-1),(1200°C,0.01 s-1)和(1200°C,0.1 s-1),不同条件下得到的晶粒尺寸不同且有未溶解碳化物。流变失稳区域有局部流变和裂纹出现。     

Cu-0.8Mg合金高温变形行为与机制

利用Gleeble-1500D热模拟试验机对Cu-0.8Mg合金进行热变形试验,变形温度为500~850℃、应变速率为0.001~10 s-1,研究不同试验条件下合金流变应力的变化规律,分析合金的流变应力、应变速率和变形温度之间的关系,对合金的热加工图进行研究。结果表明:合金在热变形过程中,其流变应力曲线表现出典型的加工硬化、动态回复和再结晶特征,随着变形温度的升高和应变速率的降低,其流变应力和峰值应力也随之降低;合金热变形过程中的激活能为177.88 k J/mol,构建了合金的本构方程;合金在热变形过程中的最优加工参数为:变形温度为700~800℃、应变速率为0.01~0.1 s-1。     

Compressive response and microstructural evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite

The hot forming behavior, failure mechanism, and microstructure evolution of in-situ TiB₂ particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300–450 °C and strain rates of 0.001-1 s^?1. The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate, and dimple rupture of the matrix at high temperature and low strain rate. Full dynamic recrystallization, which improves the composite formability, occurs under conditions of high temperature (450 °C) and low strain rate (0.001 s^?1); the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite. Based on the flow stress curves, a constitutive model describing the relationship of the flow stress, true strain, strain rate and temperature was proposed. Furthermore, the processing maps based on both the dynamic material modeling (DMM) and modified DMM (MDMM) were established to analyze flow instability domain of the composite and optimize hot forming processing parameters. The optimum processing domain was determined at temperatures of 425-450 °C and strain rates of 0.001-0.01 s^?1, in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.     

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。     

Processing map and microstructure evaluation of AA6061/Al2O3 nanocomposite at different temperatures

Hot compression behavior of Al6061/Al₂O₃ nanocomposite was investigated in the temperature range of 350–500 °C and the strain rate range of 0.0005–0.5 s^?1, in order to determine the optimum conditions for the hot workability of nanocomposite. The activation energy of 285 kJ/mol for the hot compression test is obtained by using hyperbolic sine function. By means of dynamic material model (DMM) and the corresponding processing map, safe zone for the hot workability of AA6061/Al₂O₃ is recognized at temperature of 450 °C and strain rate of 0.0005 s^?1 and at temperature of 500 °C and the strain rate range of 0.0005–0.5 s^?1, with the maximum power dissipation efficiency of 38%. Elongated and kinked grains are observed at 400 °C and strain rate of 0.5 s^?1 due to the severe deformation.     

Characterization of Hot Deformation Behavior of AMS 5708 Nickel-Based Superalloy Using Processing Map

The hot deformation behavior of AMS 5708 nickel-based superalloy was investigated by means of hot compression tests and a processing map in the temperature range of 950-1200 °C and a strain rate range of 0.01-1 s^?1 was constructed. The true stress-true strain curves showed that the maximum flow stress decreases with the increase of temperature and decrease of strain rate. The developed processing map based on experimental data, showed variations of efficiency of power dissipation relating to temperature and strain rate at constant strain. Interpretation of the processing map showed one stable domain, in which dynamic recrystallization was the dominant microstructural phenomenon, and one instability domain with flow localization. The results of interpretation of flow stress curves and processing map were verified by the microstructure observations. There are two optimum conditions for hot working of this alloy with efficiency peak of 0.36: the first is at 1150 °C for a strain rate of 1 s^?1 that produces a fine grained microstructure. The second is at 1200 °C for a strain rate of 0.01 s^?1 that produces a coarse grained microstructure.     

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.     

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.     

A Study on the Hot Deformation Behavior of Cast Mg-4Sn-2Ca (TX42) Alloy

The hot deformation behavior of as-cast Mg-4Sn-2Ca (TX42) alloy has been studied using compression tests in the temperature range of 300°C to 500°C, and strain rate range of 0.0003 s^?1 to 10 s^?1. Based on the flow stress data, a processing map has been developed, which exhibited two domains of dynamic recrystallization in the temperature and strain rate ranges: (I) 300°C to 380°C and 0.0003 s^?1 to 0.001 s^?1, and (II) 400°C to 500°C and 0.004 s^?1 to 6 s^?1. While hot working may be conducted in either of these domains, the resulting grain sizes are finer in the first domain than in the second. The apparent activation energy values estimated by kinetic analysis of the temperature and strain rate dependence of flow stress in the domains 1 and 2 are 182 kJ/mol and 179 kJ/mol, respectively. Both the values are much higher than that for self-diffusion in pure magnesium, indicating that the thermally stable CaMgSn particles in the matrix cause significant back stress during the hot deformation of this alloy. The alloy exhibits a regime of flow instability at lower temperatures and higher strain rates, which manifested as flow localization.     

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.     

Hot Workability and Flow Characteristics of Aluminum-5 wt.% B4C Composite

Flow behavior of aluminum-5 wt.% boron carbide (Al-B₄C) composite was investigated by carrying out compression tests over a range of strain rates (10^?4-10⁰ s^?1) and temperatures (200-500 °C). The flow stress data obtained from these tests at true strain 0.5 were used to develop processing map. The stable and instable flow regimes in the map were characterized by the microstructural examination using Scanning Electron Microscopy and Electron Backscattered Diffraction. The optimum condition for processing of Al-5%B₄C composite was found to lie between 425 and 475 °C at the strain rate of around 10^?4 s^?1. A strain-compensated Sellars-McG Tegart constitutive equation was established to model high-temperature deformation behavior of the material.