Ti－17合金热变形图与显微组织的对应关系

基于Ｐｒａｓａｄ等人提出的动态模拟材料模型，建立了Ｔ－１７合金在温度８０５～９４５℃、应变速率０．００１～８０ｓ（－１）范围内的热变形图。通过对能量耗散率η和组织变化分析，研究了组织稳定和失稳的参数范围。结果表明、热变形图与（α＋β）区和β区变形所得的组织完全吻合。

3003铝合金热变形机制及其加工图

对经高效熔体处理的3003铝合金进行变形温度为300～500℃、应变速率为0.01～10.0 s-1的等温压缩热模拟实验。采用材料动态模型建立该合金的热加工图,并结合OM和TEM等测试方法对热变形后的微观组织进行分析,确定了该合金的热变形机制图。结果表明:该合金加工失稳区为变形温度300～380℃、应变速率1.0～10.0 s-1的区域,热变形加工的最佳工艺参数为变形温度380～430℃、应变速率1.0～10.0 s-1,在该区域合金主要发生动态再结晶。

常规综合熔体处理的3003铝合金热变形加工图

以Gleeble-1500热/力模拟试验得到的热压缩变形数据为基础,根据DMM模型和Prasad失稳准则,分别建立功率耗散图和热加工失稳图,探讨常规综合熔体处理的3003铝合金在热压缩变形过程中热变形加工图的变化规律。结果表明:常规综合熔体处理的3003铝合金的最佳加工区域出现在中高温、中高应变速率的热变形条件下,最大功率耗散率为39.28%;在低温、高应变速率区均出现加工失稳现象,热变形加工时应尽量避免此区域。

高效综合熔体处理3003铝合金的热变形加工图

根据动态材料模型和Prasad失稳准则,利用Gleeble-1500型动态热/力模拟试验机对高效综合熔体处理的3003铝合金进行了等温热压缩试验,分别建立了功率耗散图、热加工失稳图和热变形加工图,探讨了在热压缩变形过程中该铝合金的变形规律。结果表明：3003铝合金的最佳加工区域出现在中高温、中高应变速率的热变形条件下,最大功率耗散率为55.64%;在变形温度573-648K、应变速率0.4-10s^-1的区域,以及变形温度698-773K、应变速率0.01-0.1s^-1的区域会出现加工失稳现象,热变形加工时应尽量避免此区域。

Hot deformation behavior of extruded AZ80 magnesium alloy

The hot deformation behavior of extruded AZ80 magnesium alloy was studied through hot compression tests performed at temperatures ranging from 250 to 450 ~C with strain rates varying from 0.001 to 10 s-1. The flow stress was corrected due to the deformation heating. The Zener-Hollomon parameter （Z parameter） and processing map were established to describe the hot deformation behavior. The results indicate that the applicable deformation should be conducted at the strain rate of 0.1 s-~ and the temperature range of 350-400 ~C. Besides, the relationship between the microstructure evolution and Z parameter was also discussed. High temperature and low strain rate result in a low Z parameter, which leads to full dynamic recrystallization （DRX） and large DRX grain size in the microstructure. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 400 ~C and the strain rate of 0.1 s 1.

Hot deformation behavior of TC11/Ti-22Al-25Nb dual-alloy in isothermal compression

The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Based on the experimental data,the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained.The apparent activation energy of deformation is calculated,which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90.The efficiency of power dissipation η changes obviously with the variation of deformation conditions.Under the strain rates of 0.01,0.1 and 1 s-（-1）,the value of η increases with increasing the true strain for different deformation temperatures.While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s-（-1）.The optimum processing condition is（t（opi）=1060℃,ε（opi）=0.1 s-（-1）） with the peak efficiency of 0.51.Under this deformation,dynamic recrystallization（DRX） is observed obviously in the microstructure of welding zone.Under the condition of 1060℃ and 0.001 s-（-1）,the deformation mechanism is dominated by dynamic recovery（DRV） and the value of η decreases sharply（η=0.02）.The flow instability is predicted to occur since the instability parameter ξ（ε）becomes negative.The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s-（-1） and the temperature of 900-1060℃.

Flow behavior and processing map of PM Ti-47Al-2Cr-0.2Mo alloy

The flow stress features of PM Ti-47Al-2Cr-0.2Mo alloy were studied by isothermal compression in the temperature range from 1000 to 1150 °C with strain rates of 0.001-1 s-1 on Gleeble-1500 thermo-simulation machine.The results show that the deformation temperature and strain rate have obvious effects on the flow characteristic,and the flow stress increases with increasing strain rate and decreasing temperature.The processing maps under different deformation conditions were established.The processing maps of this alloy are sensitive to strains.The processing map at the strain of 0.5 exhibits two suitable deformation domains of 1000-1050 °C at 0.001-0.05 s-1 and 1050-1125 °C at 0.01-0.1 s-1.The optimum parameters for hot working of the alloy are deformation temperature of 1000 °C and strain rate of 0.001 s-1 according to the processing map and microstructure at true strain of 0.5.

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 ℃ 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%.

Rate controlling mechanisms in hot deformation of 7A55 aluminum alloy

The hot deformation behavior of 7A55 aluminum alloy was investigated at the temperature ranging from 300 ℃ to 450 ℃ and strain rate ranging from 0.01 s-1 to 1 s-1 on a Gleeble-3500 simulator. Processing maps were established in order to apprehend the kinetics of hot deformation and the rate controlling mechanism was interpreted by the kinetic rate analysis obeying power-law relation. The results indicated that one significant domain representing dynamic recrystallization （DRX） existed on the processing maps and lying in 410-450 ＆#176;C and 0.05-1 s-1. The conclusions of kinetic analysis correlated well with those obtained from processing maps. The apparent activation energy values calculated in the dynamic recrystallization （DRX） domain and the stability regions except dynamic recrystallization （DRX） domain were 91.2 kJ/mol and 128.8 kJ/mol, respectively, which suggested that grain boundary self-diffusion and cross-slip were the rate controlling mechanisms.

Hot deformation behavior of high Ti 6061 Al alloy

The hot deformation behavior of a high Ti 6061 aluminum alloy in the temperature range from 350 to 510 ℃ and strain rate range from 0.001 to 10 s^-1 was investigated using stress-strain curve analysis, processing map, transmission electron microscopy and electron backscatter diffraction analysis. The results show that the peak stress decreases with increasing deformation temperatures and decreasing strain rate. The average deformation activation energy is 185 kJ/mol in the parameter range investigated. The flow stress model was constructed. The main softening mechanism is dynamic recovery. The processing map was obtained using dynamic material model, and the suggested processing window is 400-440℃ and 0.001-0.1 s^-1.

Hot deformation behavior of as-quenched 7005 aluminum alloy

The compressive deformation behavior of as-quenched 7005 aluminum alloy was investigated at the temperature ranging from 250 °C to 450 °C and strain rate ranging from 0.0005 s-1 to 0.5 s^-1 on Gleeble-1500 thermal-simulation machine. Experimental results show that the flow stress of as-quenched 7005 alloy is affected by both deformation temperature and strain rate, which can be represented by a Zener-Hollomon parameter in an exponent-type equation. By comparing the calculated flow stress and the measured flow stress, the results show that the calculated flow stress agrees well with the experimental result. Based on a dynamic material model, the processing maps were constructed for the strains of 0.1, 0.3 and 0.5. The maps and microstructural examination revealed that the optimum hot working domain is 270-340 °C, 0.05-0.5 s^-1 with the reasonable dynamic recrystallization. The instability domain exhibits adiabatic shear bands and flow localization, which should be avoided during hot working in order to obtain satisfactory properties.

Hot deformation behavior and microstructural evolution of beta C titanium alloy in β phase field

The hot deformation behavior of beta C titanium alloy in β phase field was investigated by isothermal compression testson a Gleeble？3800 thermomechanical simulator. The constitutive equation describing the hot deformation behavior was obtained anda processing map was established at the true strain of 0.7. The microstructure was characterized by optical microscopy （OM）,scanning electron microscopy （SEM） and electron back-scattered diffraction （EBSD） technique. The results show that the flow stressincreases with increasing strain rates, and decreases with increasing experimental temperatures. The calculated apparent activationenergy （167 kJ/mol） is close to that of self-diffusion in β titanium. The processing map and microstructure observation exhibit adynamic recrystallization domain in the temperature range of 900-1000 ℃ and strain rate range of 0.1-1 s^-1. An instability regionexists when the strain rate is higher than 1.7 s^-1. The microstructure of beta C titanium alloy can be optimized by proper heattreatments after the deformation in the dynamic recrystallization domain.

Processing map and hot deformation mechanism of novel nickel-free white copper alloy

Hot compression test of a novel nickel-free white alloy Cu?12Mn?15Zn?1.5Al?0.3Ti?0.14B?0.1Ce (mass fraction, %) was conducted on a Gleeble?1500 machine in the temperature range of 600?800 °C and the strain rate range of 0.01?10 s?1. The constitutive equation and hot processing map of the alloy were built up according to its hot deformation behavior and hot working characteristics. The deformation activation energy of the alloy is 203.005 kJ/mol. An instability region appears in the hot deformation temperature of 600?700 °C and the strain rate range of 0.32?10 s?1 when the true strain of the alloy is up to 0.7. Under the optimal hot deformation condition of 800 °C and 10 s?1 the prepared specimen has good surface quality and interior structure. The designed nickel-free alloy has very similar white chromaticity with the traditional white copper alloy (Cu?15Ni?24Zn?1.5Pb), and the color difference between them is less than 1.5, which can hardly be distinguished by human eyes.

Hot deformation behavior of homogenized Al-3.2Mg-0.4Er aluminum alloy

The hot deformation behavior of the homogenized Al?3.2Mg?0.4Er aluminum alloy was investigated at 573?723 K under strain rates of 0.001?1 s?1. On the basis of compression experimental results, an accurate phenomenological constitutive equation that coupled the effects of strain rate, deformation temperature and strain was modeled. Furthermore, a kinetic model of dynamic recrystallization and processing map were also presented. The results show that the flow stress of the studied Al?3.2Mg?0.4Er alloy can be predicted accurately using the proposed constitutive model. The evolution of microstructure and the volume fraction of dynamic recrystallization can be described exactly in terms of S-curves with the proposed kinetic model. Moreover, the processing maps for hot working at different strains were constructed, suggesting the optimum processing conditions for this alloy are 573 K, 0.001 s?1 and 723 K, 0.001?0.1 s?1.

Flow instability criteria in processing map of superalloy GH79

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79.

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

Hot deformation behavior and processing maps of as-cast Mg-8Zn-1Al-0.5Cu-0.5Mn alloy

The hot deformation behavior of as-cast Mg-8Zn-1Al-0.5Cu-0.5Mn alloy was studied by hot compression tests at temperatures of 200-350 °C and strain rates of 0.001-1 s-1.The results show that the flow stress increases significantly with increasing strain rate,and decreases as the temperature increases.The flow stress model based on the regression analysis was developed to predict the flow behavior of Mg-8Zn-1Al-0.5Cu-0.5Mn alloy during the hot compression,and the model shows a good agreement with experimental results.Meanwhile,the processing maps were established according to the dynamic materials model.The processing maps show that the increase of strain enlarges the instability domains,and the alloy shows good hot workability at high temperatures and low strain rates.

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℃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℃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℃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 ofαlamellae,whileαlamellar kinking increased.Eventually,the instability domain of flow behavior was identified in the temperature range of 850-900℃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℃and strain rate range of 0.001-0.01 s-1 was desirable leading to high efficiencies.It was realized that(950℃,0.001 s-1)was the optimum deformation condition for the alloy.

Research progress on microstructure evolution and hot processing maps of high strength β titanium alloys during hot deformation

High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.