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。     

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 behavior of AA2014 forging aluminum alloy using processing map

The hot deformation behavior of AA2014 forging aluminum alloy was investigated by isothermal compression tests at temperatures of 350–480 °C and strain rates of 0.001–1 s^?1 on a Gleeble–3180 simulator. The corresponding microstructures of the alloys under different deformation conditions were studied using optical microscopy (OM), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The processing maps were constructed with strains of 0.1, 0.3, 0.5 and 0.7. The results showed that the instability domain was more inclined to occur at strain rates higher than 0.1 s^?1 and manifested in the form of local non-uniform deformation. At the strain of 0.7, the processing map showed two stability domains: domain I (350–430°C, 0.005–0.1 s^?1) and domain II (450–480 °C, 0.001–0.05 s^?1). The predominant softening mechanisms in both of the two domains were dynamic recovery. Uniform microstructures were obtained in domain I, and an extended recovery occurred in domain II, which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries. The optimum hot working parameters for the AA2014 forging aluminum alloy were determined to be 370–420 °C and 0.008–0.08 s^?1.     

Optimization of thermal processing parameters of Ti555211 alloy using processing maps based on Murty criterion

Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001–1.000 s~(-1). The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress–strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol~(-1)in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A *60 % peak efficiency occurs at 800–850 °C/0.001–0.010 s~(-1). The other peak efficiency of *60 % occurs at C950 °C/0.001–0.010 s~(-1), which can be considered to be the optimum condition for high-temperature working of this alloy.However, at strain rates of higher than 1.000 s~(-1)and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.     

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.     

Hot working behavior of near alpha titanium alloy analyzed by mechanical testing and processing map

The hot deformation characteristics of the Ti−5.7Al−2.1Sn−3.9Zr−2Mo−0.1Si (Ti-6242S) alloy with an acicular starting microstructure were analyzed using processing map. The uniaxial hot compression tests were performed at temperatures ranging from 850 to 1000 °C and at strain rates of 0.001−1 s⁻¹. The developed processing map was used to determine the safe and unsafe deformation conditions of the alloy in association with the microstructural evolution by SEM and OM. It was recognized that the flow stress revealed differences in flow softening behavior by deformation at 1000 °C compared to the lower deformation temperatures, which was attributed to microstructural changes. The processing map developed for typical strain of 0.7 in two-phase field exhibited high efficiency value of power dissipation of about 55% at 950 °C and 0.001 s⁻¹, basically due to extensive globularization. An increase in strain rate and a decrease in temperature resulted in a decrease in globularization of α lamellae, while α lamellar kinking increased. Eventually, the instability domain of flow behavior was identified in the temperature range of 850−900 °C and at the strain rate higher than 0.01 s⁻¹ reflecting the flow localization and adiabatic shear banding. By considering the power efficiency domains and the microstructural observations, the deformation in the temperature range of 950−1000 °C and strain rate range of 0.001−0.01 s⁻¹ was desirable leading to high efficiencies. It was realized that (950 °C, 0.001 s⁻¹) was the optimum deformation condition for the alloy.     

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。     

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.     

60NiTi合金的热压缩变形与显微组织演变（英文）

采用Gleeble-3500热模拟试验机对在变形温度500～650℃和应变速率0.001～1 s^-1条件下的60NiTi合金进行热压缩变形,分析其热变形行为和显微组织,建立变形本构模型,绘制热加工图。结果表明,当压缩温度升高或应变速率降低时,峰值应力减小。合金的热变形激活能为327.89 k J/mol,热加工工艺参数为变形温度600～650℃和应变速率0.005～0.05 s^-1。当变形温度升高时,合金的再结晶程度增大;当应变速率增大时,位错密度和孪晶数量增大,Ni₃Ti相易于聚集;Ni₃Ti析出相有利于诱发合金基体的动态再结晶。动态回复、动态再结晶和孪生是60NiTi合金热变形的主要机制。     

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%.     

铸态粗晶Ti-5553钛合金高温变形行为与机理研究

本文借助Gleeble-3800热模拟试验机系统地研究了铸态粗晶Ti-5553合金在温度700 ℃~1100 ℃、应变速率为0.001 s_^-1~10 s_^-1条件下的高温变形行为。研究结果表明合金的流变应力对变形温度和速率都有强敏感性,流变软化过程也随变形参数的改变呈现出不同的模式。通过经典的动力学模型,建立了合金高温变形的本构关系和激活能分布图,进一步基于动态材料模型构建了合金的热加工图并实现了对不同加工区间变形机制的识别。合金在低温区(700 ℃)和高速率区( 1 s_^-1)均展现出失稳变形的特征,包括外部开裂、绝热剪切带、局部流变等机制,在实际加工中应对这些加工区域进行规避。合金在800 ℃及中低速率( 0.1 s_^-1)变形下的主导机制为α相的动态析出,在中高温(900 ℃-1100 ℃)及中低速率变形下的主导机制为动态回复与动态再结晶的结合。此外,合金在高温较低应变速率(1100 ℃/0.01 s_^-1)条件的变形中表现出大范围动态再结晶的行为特点并伴随稳定的流变软化,因此此条件附近的参数区间被认定为该合金的最优加工窗口,应在实际加工中给予优先考虑。     

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.     

ZL270LF铝合金的热变形行为与组织演变

通过热压缩实验研究了ZL270LF铝合金在变形量为70%,温度为300~550 ℃,应变速率为 0.01~10 s^-1范围的热变形行为,建立了流变应力本构方程模型,绘制出了二维热加工图,确定了最佳热加工区域,采用电子背散射衍射（EBSD）和透射电子显微镜（TEM）技术研究了该合金的组织演变规律。结果表明：ZL270LF铝合金的流变应力随变形温度的升高和应变速率的降低而降低,热变形激活能为309.05 kJ/mol,最优热加工区为温度470~530 ℃、应变速率为0.01~1 s^-1。该合金在热变形过程中存在3种不同的DRX机制,即连续动态再结晶（CDRX）、不连续动态再结晶（DDRX）和几何动态再结晶（GDRX）,其中CDRX是ZL270LF铝合金动态再结晶的主要机制。     

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)。     

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.     

Hot Deformation Mechanisms of an As-Extruded TiAl Alloy with Large Amount of Remnant Lamellae

The hot deformation mechanisms of an as-extruded Ti-44Al-5V-1Cr alloy with a large amount of remnant lamellae were investigated by hot compression tests at temperatures of 900-1250 °C and strain rates of 0.001-1 s^?1. The hot processing map of the as-extruded Ti-44Al-5V-1Cr alloy was developed on the basis of dynamic materials modeling and the Prasad criteria. There were four different domains in the hot processing map, according to the efficiency of power dissipation, η. The flow soft and hot deformation mechanisms for different domains were illustrated in the context of microstructural evolution during the process of deformation. As a result, the dynamic recrystallization and superplastic deformation occurred at 1125-1150 °C near 0.001 s^?1, and this region is suitable for superplastic forming. The α phase dynamic recrystallization and dynamic recovery occurred at 1250 °C and 0.1 s^?1. The existence of small amount of the γ and β phases effectively inhibited the growth of α grains.     

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.     

Flow stress and dynamic recrystallization behavior of Al-9Mg-1.1Li-0.5Mn alloy during hot compression process

The flow stress behavior of spray-formed Al-9Mg-1.1Li-0.5Mn alloy was studied using thermal simulation tests on a Gleeble-3500 machine over deformation temperature range of 300-450 °C and strain rate of 0.01-10 s^?1. The microstructural evolution of the alloy during the hot compression process was characterized by transmission electron microscopy (TEM) and electron back scatter diffractometry (EBSD). The results show that the flow stress behavior and microstructural evolution are sensitive to deformation parameters. The peak stress level, steady flow stress, dislocation density and amount of substructures of the alloy increase with decreasing deformation temperature and increasing strain rate. Conversely, the high angle grain boundary area increases, the grain boundary is in serrated shape and the dynamic recrystallization in the alloy occurs. The microstructure of the alloy is fibrous-like and the main softening mechanism is dynamic recovery during steady deformation state. The flow stress behavior can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation with the hot deformation activation energy of 184.2538 kJ/mol. The constitutive equation and the hot processing map were established. The hot processing map exhibits that the optimum processing conditions for Al-9Mg-1.1Li-0.5Mn alloy are in deformation temperature range from 380 to 450 °C and strain rate range from 0.01 to 0.1 s^?1.     

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.