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Hot compression deformation behaviors of medium carbon Cr-Ni-Mo-Nb steel were investigated at deformation temperatures ranging from 1223 to 1423 Kand strain rates of 0.1,1and 5s-1.Dynamic recovery(DRV)and dynamic recrystallization(DRX)were observed during the hot compression deformation.For all of the samples,DRX occurred at deformation temperatures above 1323 Kat different strain rates,while below 1223 K,no DRX was observed.The activation energy of the tested steel was determined as 386.06kJ/mol.The ratio of critical stress to peak stress and the ratio of critical strain to peak strain were 0.835 and 0.37,respectively.Kinetic equations interpreting the DRX behavior of the tested steel were proposed,and the corresponding parameters including the volume fraction and the average grain size were determined.Moreover,the microstructures induced under different deformation conditions were analyzed. 相似文献
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Twinning induced plasticity (TWIP) steels, which rely on high Mn contents to promote twinning as the deformation mechanism, exhibit high ultimate strengths together with outstanding combinations of ultimate strength and ductility. In terms of mechanical properties, one of the most important microstructural features is grain size. The knowledge of the kinetics of recrystallization mechanisms, i.e., dynamic recrystallization (DRX) and static recrystallization (SRX), can be used in order to control the grain size of the final product by a proper rolling schedule design. The focus of this work is the characterization of the DRX kinetics of two TWIP steels. The basic composition of the steels is Fe–21Mn–0.4C–1.5Al–1.5Si, and one of them is further alloyed with 0.12% V. With this objective, compression tests were carried out at 900, 1000, and 1100°C and strain rates ranging from 1 × 10?1 s?1 to 1 × 10?4 s?1. Furthermore, metallographic observation by optical microscopy (OM) was done to assess the evolution of grain size for the different deformation conditions. According to the results, the existence of V in the composition does not affect the hot flow behavior of the steel, although recrystallization fraction and recrystallized grain size decrease for the V‐containing steel. 相似文献
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《钢铁研究学报(英文版)》2016,(3):244-252
Hot compression tests were carried out in the temperature range of 1 223-1 473 Kand strain rate range of0.01-30s-1 to investigate the flow behavior and microstructural evolution of super duplex stainless steel 2507(SDSS2507).It is found that most of the flow curves exhibit a characteristic of dynamic recrystallization(DRX)and the flow stress increases with the decrease of temperature and the increase of strain rate.The apparent activation energy Qof SDSS2507 with varying true strain and strain rate is determined.As the strain increases,the value of Qdeclines in different ways with varying strain rate.The microstructural evolution characteristics and the strain partition between the two constituent phases are significantly affected by the Zener-Hollomon parameter(Z).At a lower lnZ,dynamic recovery(DRV)and continuous dynamic recrystallization(CDRX)of the ferrite dominate the softening mechanism during the compression.At this time,steady state deformation takes place at the last stage of deformation.In contrast,a higher lnZ will facilitate the plastic deformation of the austenite and then activate the discontinuous dynamic recrystallization(DDRX)of the austenite,which leads to a continuous decline of the flow stress even at the last deformation stage together with CDRX of the ferrite. 相似文献
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45钢低温区热变形行为研究 总被引:1,自引:0,他引:1
利用Gleeble-1500热模拟试验机研究了不同变形条件对45钢低温区热变形行为的影响。试验结果表明:峰值应力随变形温度的降低和应变速率的提高而增大;当应变速率[ε]≥0.01s-1、变形温度 [t]<500 ℃时,发生动态回复;当应变速率[ε]≤1s-1、变形温度[t]≥500 ℃时,发生动态再结晶。在Sellars -Tegart方程的基础上,建立了45钢低温区加工硬化-动态回复、动态再结晶2阶段流变应力模型;根据试验结果计算拟合了模型中各参数。采用建立的流变应力模型成功预测了动态回复、动态再结晶型应力-应变曲线。利用上述模型对45钢中厚板轧后低温工业热矫直的矫直力进行了预测,其结果与实测值吻合良好。 相似文献
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通过分析不同变形温度及应变速率下低硅含磷系TRIP钢高温流变曲线的变化规律,建立了本构关系,并分析了合金元素钒对其影响。结果表明,添加0.19%钒,由于固溶钒原子的拖曳作用,使动态再结晶激活能提高~6%,同时推迟了动态再结晶的发生,使σc/σp和εc/εp值均有所提高。通过回归得到无钒钢和含钒钢的峰值应力和临界应力、峰值应变和临界应变与lnZ的关系。 相似文献
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The 34CrMo4(AISI 4130)steel is extensively utilized in the compressed natural gas cylinders.Due to the importance of thermomechanical processing in the production of these cylinders,the dynamic recrystallization(DRX)characteristics of 34CrMo4 steel were investigated.The effect of hot deformation parameters such as temperature and strain rate on the dynamic restoration processes of a 34CrMo4 alloy was studied.Hot compression tests were performed in the temperature range of 900 to 1100 ℃ and the strain rate r... 相似文献
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The 4340 steel is extensively utilized in several industries including automotive and aerospace for manufacturing a large number of structural components. Due to the importance of thermo-mechanical processing in the production of steels, the dynamic recrystallization (DRX) characteristics of 4340 steel were investigated. Namely, hot compression tests on 4340 steel have been performed in a temperature range of 900–1200 °C and a strain rate range of 0. 01–1 s?1 and the strain of up to 0. 9. The resulting flow stress curves show the occurrence of dynamic recrystallization. The flow stress values decrease with the increase of deformation temperature and the decrease of strain rate. The microstructure of 4340 steel after deformation has been studied and it is suggested that the evolution of DRX grain structures can be accompanied by considerable migration of grain boundaries. The constitutive equations were developed to model the hot deformation behavior. Finally based on the classical stress-dislocation relations and the kinematics of the dynamic recrystallization; the flow stress constitutive equations for the dynamic recovery period and dynamic recrystallization period were derived for 4340 steel, respectively. The validity of the model was demonstrated by demonstrating the experimental data with the numerical results with reasonable agreement. 相似文献
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High temperature deformation characteristics of a semiaustenitic grade of precipitation hardening stainless steels were investigated by conducting hot compression tests at temperatures of 900-1 100 ℃ and strain rates of 0001-1 s-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization (DRX) was responsible for flow softening. The correlation between critical strain for initiation of DRX and deformation parameters including temperature and strain rate, and therefore, Zener Hollomon parameter (Z) was studied. Metallographic observation was performed to determine the as deformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed. 相似文献
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用Gleeble-3500热力模拟试验机在温度为1 223~1 323 K,应变速率为0.2~10 s-1的条件下对一种非调质连杆用高碳微合金钢进行了热压缩变形试验,测得了其流变曲线,并观察了变形后的组织.试验结果表明,流变应力和峰值应变随变形温度的降低和应变速率的提高而增大.试验用钢在真应变为0.8,温度为1 223~1 323 K,应变速率为0.2~10 s-1的条件下,发生完全动态再结晶.测得试验用钢的热变形激活能为289.9 kJ/mol,并得出了其热变形方程,以及动态再结晶晶粒尺寸与Zener-Hollomon参数之间的关系和动态再结晶状态图. 相似文献
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《钢铁研究学报(英文版)》2016,(2):178-184
Hot deformation behavior of superaustenitic stainless steel S32654 was investigated with hot compression tests at temperatures of 950-1 250 ℃ and strain rates of 0.001-10s~(-1).Above 1 150 ℃,with strain rate lower than 0.1s~(-1),the flow curves exhibit nearly steady-state behavior,while at higher strain rate,continuous flow softening occurs.To provide a precise prediction of flow behavior for the alloy,the constitutive modeling considering effect of strain was derived on the basis of the obtained experimental data and constitutive relationship which incorporated Arrhenius term and hyperbolic-sine type equation.The material constantsα,n,Q and lnA are found to be functions of the strain and can be fitted employing eighth-order polynomial.The developed constitutive model can be employed to describe the deformation behavior of superaustenitic stainless steel S32654. 相似文献
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The hot deformation behavior of a new heat resistant steel G115 designed for 650 °C ultra-supercritical (USC) power plants was experimentally studied. Hot compression test was carried out in the temperature range of 900 — 1200 °C and the strain rate range of 0.1 — 20 s?1 by using Gleeble-3800 thermal-mechanical simulator, and the corresponding flow curves were obtained. Experimental results show that the flow stress increases with the decrease of deformation temperature and the increase of strain rate. The hot deformation activation energy of G115 steel was determined to be 494 kJ/mol and the constitutive equation was also obtained. For convenience of the practical application, a good approximate equation was obtained for calculating the peak stress values of G115 steel under different deformation conditions. At the strain value of 0. 9, natural logarithm of the critical Zener-Hollomon parameter Ze of G115 steel was determined to be in the scope of 49. 67 and 50. 65, above which there will be no dynamic recrystallization (DRX). And natural logarithm of the critical Zener-Hollomon parameter Zs of G115 steel was determined to be in the scopes of 45. 58 and 46. 27, below which full DRX may occur. Then, the status diagram of dynamic microstructures of G115 steel was established. In addition, the strain rate sensitivity of G115 steel is not constant during the test temperature range and it increases linearly from 900 to 1200 °C. Therefore, hot deformation at higher temperatures would obtain better workability. 相似文献
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En-xiang PU Wen-jie ZHENG Zhi-gang SONG Jin-zhong XIANG Xian-ping WEI 《钢铁研究学报(英文版)》2014,21(10):975-982
Hot compression tests were conducted on a Gleeble-3800 machine in a temperature range of 950 to 1200 ℃ and a strain rate range of 0. 001 to 10 s-1 in order to study the hot deformation behaviour of superaustenitic stainless steel 654SMO. The results show that peak stress increases with decreasing temperature and increasing strain rate, and the apparent activation energy of this alloy was determined to be about 494 kJ/mol. The constitutive equation which can be used to relate the peak stress to the absolute temperature and strain rate was obtained. The processing maps for hot working developed on the basis of flow stress data and the dynamic materials model were adopted to op- timize the hot workability. It is found that the features of the maps obtained in the strain range of 0.2 to 1.0 are fun- damentally similar, indicating that the strain does not have a substantial influence on processing map. The combina- tion of processing map and mierostructural observations indicates that the favorable hot deformation conditions are located in two domains of processing map. The first domain occurs in the temperature range of 980 to 1035 ℃ and strain rate range of 0. 001 to 0.01 s-1 with a peak efficiency of 55%. The second domain appears in the temperature range of 1 120 to 1 180 ℃ and strain rate range of 0.3 to 3 s-1 with peak efficiency of 35%. Compared to other stable domains, the specimens deformed in these two domains exhibit full dynamic recrystallization grains with finer and more uniform sizes. An instability domain occurs at temperatures below 1 100 ℃ and strain rate above 0.1 s-1 , and flow instability is manifested in the form of flow localization. 相似文献
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《钢铁研究学报(英文版)》2016,(12):1342-1348
A hot compression experiment (1 073-1 473 K,strain rates of 0.001-10 s-1 )of SA508GR.4N low alloy steel was performed using a Gleeble-3800 thermal-mechanical simulator,and the hot deformation behavior of the steel was investigated by analyzing both the true stress-true strain curves and its microstructures.The thermal de-formation equation and hot deformation activation energy (Q)of SA508GR.4N steel were obtained by regression with a classic hyperbolic sine function.The hot processing map of SA508GR.4N steel was also established.An em-pirical equation for the stress peak was described for practical applications.The SA508GR.4N steel showed a critical Zener-Hollomon parameter (lnZc)for dynamic recrystallization (DRX)of 37.44,below which full DRX may occur. The sensitivity of the SA508GR.4N steel increased linearly with test temperature,such that higher temperatures led to enhanced workability. 相似文献