电热合金Cr20 Ni80的热变形行为及热加工图

为了解决Cr20Ni80电热合金锻造开裂的问题,在Gleeb-1500D热模拟试验机上对该合金进行热压缩试验,研究变形温度为900~1220℃,应变速率为0.001~10 s-1条件下的热变形行为,并根据动态材料模型建立合金的热加工图.合金的真应力-真应变曲线呈现稳态流变特征,峰值应力随变形温度的降低或应变速率的升高而增加;热变形过程中稳态流变应力可用双曲正弦本构方程来描述,其激活能为371.29 k J·mol-1.根据热加工图确定了热变形流变失稳区及热变形过程的最佳工艺参数,其加工温度为1050~1200℃,应变速率为0.03~0.08 s-1.优化的热加工工艺在生产中得到验证.     

Fe16Mn0.6C TWIP钢流变应力和临界动态再结晶行为

 利用Thermecmastor-Z热模拟实验机，得到了Fe16Mn0.6C TWIP钢在变形温度850~1150℃，应变速率0.03~30s-1条件下热压缩变形的真应力应变曲线。进而研究了变形温度、应变速率对Fe16Mn0.6C流变应力和临界动态再结晶行为的影响规律。结果表明，850~1150℃范围内Fe16Mn0.6C热变形的峰值应力随温度的升高而降低，随着应变速率的增大而升高；且在应变速率为0.03 s-1和30 s-1出现明显的应力峰值，材料发生了动态再结晶。最后采用线性回归方法计算出Fe16Mn0.6C的高温变形流变应力本构方程，得出热变形激活能为469kJ/mol；并通过应变硬化速率与流变应力曲线求出了该钢种动态再结晶临界条件与Z参数之间的关系。     

2Cr12NiMo1W1V超临界汽轮机叶片用耐热钢的热变形行为

 为了解决2Cr12NiMo1W1V耐热钢在锻造过程中晶粒粗大和组织不均匀的问题，利用Gleeble-3800热模拟试验机，在变形温度为1 000～1 200 ℃、应变速率为0.01～10 s－1、变形量为70%的条件下，研究和分析了2Cr12NiMo1W1V耐热钢的高温塑性变形和动态再结晶行为。结果表明，该耐热钢的真应力-应变曲线具有动态再结晶特征。再结晶晶粒尺寸随着变形温度的增加或应变速率的降低呈增加趋势，在变形温度为1 150～1 200 ℃，应变速率为0.01 s－1时，晶粒尺寸急剧增加。在真应力-应变曲线的基础上，建立了材料热变形本构方程，其热激活能为453.74 kJ/mol。根据峰值应力绘制了合金的热加工图并获得在各加工条件下的效率值，合金的最佳热加工区间为变形温度为1 000～1 150 ℃、应变速率为0.1～1 s－1以及变形温度为1 060～1 125 ℃、应变速率为0.1～10 s－1。     

14Cr-ODS铁素体钢的热变形行为及热加工图

利用Gleeble-1500D热模拟实验机研究机械合金化法制备的14Cr-ODS铁素体钢在变形温度为1 050~1 200℃、应变速率为0.001~0.3 s 1条件下的高温变形行为,测定其真应力真应变曲线,分析流变应力随应变速率以及变形温度的变化关系。应用MATLAB软件计算最佳的应力水平参数,通过线性回归分析得出材料的变形激活能、材料常数和材料的双曲线本构方程,构造14Cr-ODS铁素体钢的热加工图。结果表明:14Cr-ODS铁素体钢的流变应力随温度升高而减小,随应变速率增加而增大;其变形激活能为501.11 kJ/mol,最佳应力水平参数为0.007,应力指数为4.08;加工失稳温度区域为1 050~1 100℃,应变速率区域为0.1~0.3 s 1;适合加工的条件是变形温度为1 150℃,应变速率为0.1 s 1。     

Cu-Cr-Zr合金的热变形行为

采用Gleeble-3500热模拟实验机对Cu-Cr-Zr合金进行了压缩变形实验,分析了在变形温度为25~700℃、应变速率为0.0001~0.1000s-1的条件下流变应力的变化规律,利用扫描电镜及透射电镜分析合金在热压缩过程中的组织演变及动态再结晶机制。结果表明:Cu-Cr-Zr合金在热变形过程中发生了动态再结晶,且变形温度和应变速率均对流变应力有显著的影响,流变应力随着变形温度的升高而降低,随着应变速率的增加而升高,说明该合金属于正应变速率敏感材料;当变形温度为400~500℃时,低应变速率(0.0001~0.0010 s-1)的真应力-真应变曲线呈现动态再结晶曲线特征,高应变速率(0.01~0.10 s-1)的真应力-真应变曲线呈现动态回复特征;在真应力-真应变曲线的基础上,采用双曲正弦模型能较好地描述Cu-Cr-Zr合金高温变形时的流变行为,建立了完整描述合金热变形过程中流变应力与应变速率和变形温度关系的本构方程,确定了合金的变形激活能为311.43 kJ·mol-1。     

30% SiC_p/2024Al复合材料的热变形行为

在Gleeble-1 500D热模拟机上采用等温压缩实验研究30%SiC_p/Al复合材料的高温压缩变形行为,获得该材料在温度为623~773 K,应变速率为0.01-10 s~(-1)的条件下的真应力-应变曲线,并在考虑摩擦和变形热效应的基础上对真应力-应变曲线进行修正。对修正后的峰值应力进行线性回归,建立该材料的本构方程。根据材料动态模型,计算并建立30%SiC_p/Al复合材料的热加工图,据此确定热变形流变失稳区。在应变速率为0.01 s~(-1)时,随热变形温度升高,该复合材料发生动态再结晶的体积分数增加。     

ODS-310合金的热变形行为及热加工图

采用Gleeble-1500D热模拟试验机研究机械合金化制备的ODS-310合金在变形温度为1 050~1 150℃、应变速率为0.001~1 s-1条件下的高温变形行为,测定其真应力-应变曲线,分析其流变应力与应变速率及变形温度三者之间的关系,并采用Zener-Hollomon参数法建立ODS-310合金的高温变形本构方程,基于动态材料模型,构造ODS-310合金的热加工图。结果表明:ODS-310合金的流变应力随变形温度降低或应变速率提高而增大;该合金热变形过程中的流变行为可用双曲线正弦模型来描述,在实验条件下的平均变形激活能为828.384 kJ/mol;真应变为0.4的热加工图表明,ODS-310合金在高温变形时存在2个加工失稳区,即变形温度为1 050~1 070℃、变形速率为0.01~1s-1的区域,和变形温度为1 130~1 150℃、变形速率为0.1~1 s-1的区域;ODS-310合金的最佳变形温度和应变速率分别为1 150℃和0.001 s-1。     

高N马氏体不锈轴承钢的热变形行为

利用Gleeble-3800热模拟试验机在温度为1 040~1 120℃,应变速率为1~20s-1的条件下进行了高N马氏体不锈轴承钢的热压缩变形试验。结合真应力-真应变曲线和热变形组织研究了变形参数对高N马氏体不锈轴承钢的热变形行为和碳氮化物演变规律的影响。结果表明:在该变形条件下,试验钢的真应力-真应变曲线为动态再结晶型。随着应变量的增大,碳化物的平均尺寸呈减小趋势,但数量有所增多。基于热变形方程计算得到的应变量为0.6时的热变形激活能Q为410.7kJ/mol。构建了包含应变量在内的流变应力方程,同时建立了高N马氏体不锈轴承钢的Zener-Hollomon参数本构方程。     

Monel K-500合金高温流变特性及其本构方程

采用Gleeble 3800热模拟实验机研究了Monel K-500合金在变形温度为850~1 100℃,应变速率为0.01~10s-1时的高温流变行为,测定了合金在不同条件下的流变应力曲线。结果表明,最大压缩变形量对合金的流变行为影响不大;变形温度相同时,合金在应变速率为0.1s-1时取得最大峰值应变;根据Arrhenius模型得到了合金的热变形本构方程。     

0.07C-0.85Mn-0.16S-0.05Bi钢的热变形行为

采用MMS-200热力模拟试验机,在变形温度950 ～1200℃以及变形速率0.01～10 s-1条件下对0.07C-0.85Mn-0.16S-0.05Bi钢进行一系列热压缩实验.结果 表明,实验钢的流变应力曲线呈现明显的动态再结晶特征,并且流变应力随变形温度的提升或者应变速率的下降而降低.根据不同变形条件下的峰值应力,由Arrhenius模型构建了峰值应力下的本构方程,计算实验钢热变形激活能Q并基于动态材料模型绘制真应变为0.1、0.3、0.5、0.7的热加工图.研究分析了实验钢在不同应变下的失稳区域和合理热加工区域,随着应变的增大,失稳区均出现在高速率变形区,且由低温高速率区向高温高速率区转变.最佳热加工参数为变形温度1020～1200℃、变形速率0.01～0.3 s-1.     

Constitutive Equations for Flow Behavior of Powder-forged Fe-0.5C-2Cu Steel under Hot Compression

To investigate the hot deformation behavior of powder-forged(P/F)Fe-0.5C-2Cu steel,the hot compression tests were conducted at temperatures ranging from 900to 1 000 ℃ and strain rates from 0.1to 10s-1 using Gleeble-1500thermal simulator.The true stress-true strain curves at different temperatures and strain rates of P/F steel were obtained.It is found that dynamic recovery only occurs as strain rate is 10s-1 at 900℃,and the dynamic recrystallization is the main softening mechanism.The flow stress increases with decreasing temperature and increasing strain rate.The experimental data are employed to develop constitutive equations on the basis of the Arrheniustype equation by introducing the strain with nonlinear fitting.The flow stresses predicted by the proposed constitutive equations are in good agreement with the experimental values,and the correlation coefficient(R2)and the average absolute relative error(AARE)are 0.995 25and 3.07%respectively.These results indicate the proposed constitutive equations can effectively describe the hot deformation behavior of the material.     

Hot Deformation Behavior of Nickel-Based Superalloy GH4720Li

 The hot deformation characteristics of GH4720Li alloy were studied at the temperature of 1100-1170 ℃ and strain rate of 001-1 s-1 using Gleeble hot compression tests. True stress-true strain curves and deformation microstructures were investigated. Constitutive equation was established using the hyperbolic law. Processing map for hot working was also developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate. The results show that dynamic recrystallization is the dominant softening mechanism during hot deformation. Fully recrystallized grain is obtained at strain of 07 above 1130 ℃, and coarsening occurs above 1150 ℃. The mean deformation activation energy is determined to be 512 kJ/mol. According to the low activation energy value, high dissipation efficiency parameter and fine recrystallized microstructure, 1130 ℃ is chosen as the hot working temperature for GH4720Li alloy.     

Hot Deformation Behavior of SA508GR.4N Steel for Nuclear Reactor Pressure Vessels

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.     

医用镍钛合金的制备与热压缩变形行为

采用真空感应熔炼法制备了医用Ti-50. 7%Ni合金(原子数分数), 测试了铸态合金的成分、相变点、微观组织和硬度, 并采用Gleeble-3800热模拟实验机在变形温度750~950℃、应变速率0. 001~1 s-1, 应变量为0. 5的条件下对Ni-Ti合金进行高温压缩变形, 分析其流动应力变化规律, 建立了高温塑性变形本构关系和热加工图.结果表明: 当变形温度减小或应变速率增大时, Ni-Ti合金的流动应力会随之增大.应变速率为1 s-1时, 合金的真应力-真应变曲线呈现出锯齿状特征.根据热加工图, 获得了Ni-Ti合金的加工安全区和流变失稳区, 进而确定其合理的热变形温度范围为820~880℃, 真应变速率低于0. 1 s-1.从而为制定镍钛合金的锻造工艺参数提供理论和数据基础.      

03Cr18NiMoN节镍双相不锈钢的热变形行为及热加工图

关键词：双相不锈钢； 流变曲线； 本构方程； 热加工图     

Hot Deformation Behaviors of S31042 Austenitic Heat-Resistant Steel

 The hot deformation behavior of S31042 austenitic heat-resistant steel was investigated over the temperature range of 900-1200 ℃ and strain rate range of 001-10 s-1 using hot compression tests and the corresponding flow curves were obtained. The hot deformation activation energy of the test steel is 625 kJ/mol. The hot deformation equation and the relationship between the peak stresses, deformation temperature and strain rate were set up. The Zener-Hollomon parameter under various conditions was determined. The relation between the Zener-Hollomon parameter and the microstructure evolution of test steel was discussed. With the decrease of Zener-Hollomon parameter, the microstructure of test steel transforms from deformation instability to dynamic recovery, partial dynamic recrystallization, full dynamic recrystallization with equiaxial structure, and finally to full dynamic recrystallization with mixed crystal structure. The deformation condition can be adjusted easily by utilizing the Zener-Hollomon parameter to obtain equiaxial microstructure.     

新型奥氏体耐热不锈钢C-HRA-5的热变形行为

为了获得C HRA 5钢轧制生产的最佳工艺参数,采用Gleeble 3800热力模拟试验机对C HRA 5钢进行了双道次热压缩实验。实验在变形温度范围为900~1100℃,应变速率范围为001~1s-1,道次间隙时间分别为1、5、15、30s的条件下获得C-HRA -5钢的真应力 应变曲线。采用0.2%补偿法计算得到了软化分数,且软化分数随变形温度的升高和应变速率的增大而增加。通过线性回归分析得到了MDRX的动力学方程。建立的C-HRA-5钢热加工图表明材料在1000~1100℃的范围内变形稳定。此外,道次间隙时间为5s时,C-HRA-5钢在较低温度下进行第2道次压缩的过程中不会出现失稳。     

Constitutive Modeling for Flow Behaviors of Superaustenitic Stainless Steel S32654 during Hot Deformation

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.     

Constitutive Equation Models of Hot-Compressed T122 Heat Resistant Steel

 Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate (001 to 10 s-1) and temperature (900 to 1200 ℃) with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantitatively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in austenite temperature scope.