一种非调质连杆用高碳微合金钢的热变形行为

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.     

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。     

胀断连杆用高钒中碳钢的动态再结晶行为

利用Gleeble 3800热模拟试验机进行单道次压缩试验,研究了1种新型胀断连杆用高钒中碳钢37MnSiVS在900~1 150℃温度区间和0.1~10s-2变形速率条件下的动态再结晶行为。结果表明:试验料的热变形特征与传统的中碳微合金钢基本一致,较高的温度和较低的应变速率有利于发生动态再结晶。试验料在变形温度低于1 000℃时开始发生再结晶的时间进一步延长。透射电镜(TEM)观察结果表明,试验料中的钒主要以固溶态的形式存在于奥氏体中,从而影响奥氏体的动态再结晶行为。所获得的试验料的热变形激活能为364.9kJ/mol,并得出了其热变形方程及动态再结晶晶粒尺寸与Zener-Hollomon参数之间的关系式。     

Hot Deformation Behavior of a New 9%Cr Heat Resistant Steel G115

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 Z_e 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 Z_s 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.     

Study on dynamic recrystallization behavior of hot rolled TRIP steel produced by CSP process

The dynamic recrystallization behavior of hot rolled TRIP steel produced by CSP process was studied by means of Gleeble-3500 thermal simulation testing machine in the temperature range of 950-1150℃ with the strain rate of 0.1-10s-1 and the strain of 65%. And the effect of initial austenite grain size on the dynamic recrystallization behavior of TRIP steel was explored. The results show that the finer initial austenite grain size, the higher deformation temperature and the lower strain rate, the more positive austenite dynamic recrystallization of TRIP steel. Moreover, it is found that when the coarse grained samples (initial austenite grain size is 767.54μm) deform in the range of 1050℃ to 1150℃, the austenite dynamic recrystallization will take place, and the dynamic recrystallization activation energy of TRIP steel is deduced as 361539.17J/mol. The Zener-Hollomon parameter equation as a function of strain rate and temperature is determined. And the model of critical strain for dynamic recrystallization, the flow stress model of austenite at high temperature and the grain size model for dynamic recrystallization are also established. The calculation results are coincided well with the experimental results.     

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。     

CSP热轧TRIP钢动态再结晶行为研究

摘要：采用Gleeble-3500热模拟试验机,在温度为950~1150℃、应变速率为0.1~10s-1和变形量为65%的条件下研究了CSP热轧TRIP钢的动态再结晶行为,探讨了初始奥氏体晶粒尺寸对TRIP钢动态再结晶行为的影响。研究结果表明,初始奥氏体晶粒尺寸越小,变形温度越高,应变速率越慢时,TRIP钢中奥氏体越易发生动态再结晶。其中,粗晶试样（初始奥氏体晶粒尺寸为767.54μm）在1050~1150℃内变形时,将发生动态再结晶。其热变形激活能为361539.17J/mol,确定了Zener-Holloman参数与应变速率和温度的关系式,建立了动态再结晶临界应变模型、高温奥氏体流动应力模型和动态再结晶晶粒尺寸模型,理论模拟结果与试验结果吻合较好。     

Hot Compression Behavior of AsCast Precipitation Hardening Stainless Steel

 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 0001-1 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.     

20CrMnTiH钢唯象本构模型及动态再结晶行为

 采用Gleeble-3800热模拟试验机对20CrMnTiH钢进行了等温热压缩试验,研究了该钢在变形温度为850～1 150 ℃、应变速率为0.01～10 s－1条件下的高温热变形行为,运用数学回归方法和热力学不可逆原理,建立了20CrMnTiH钢应变补偿的唯象本构方程和动态再结晶模型,并对该应变补偿的唯象本构模型进行了有效验证。在真应力-真应变曲线中,变形温度和应变速率对20CrMnTiH钢的流变应力影响显著,表现出正的应变速率敏感性和负的温度敏感性;由本构模型计算得到的流变应力值与试验值两者之间有很好的相关性[(R＝0.976 64),]平均相对误差为5.544 2%;在应变硬化速率与流变应力关系曲线中,利用单一参数法和求解拐点法获得了不同变形条件下动态再结晶的临界应力[σc]和临界应变[εc]值,建立了临界应力、临界应变和Zener-Hollomon参数的数学模型[ε≥εc＝][0.007 9 lnZ－0.153 23,]且临界应变[εc]随着温度补偿应变速率因子[Z]的增加而增加。     

铸态超级双相不锈钢S32750热加工性能

 为研究热变形参数对铸态超级双相不锈钢S32750热变形行为和显微组织的影响,运用Gleeble-3800热模拟试验机对S32750进行不同温度和应变速率下的高温拉伸和压缩试验。结果表明,S32750在1000~1200℃范围内具有较好的热塑性。在变形温度较低、应变速率较低时,流变曲线表现出不同于单相不锈钢的“类屈服平台”特征;当应变速率较高或变形温度较高、应变速率较低时,流变曲线为典型的动态再结晶特征。微观组织演变显示,铁素体和奥氏体两相都发生动态再结晶,且铁素体的再结晶先于奥氏体。降低应变速率,提高变形温度,可促进动态再结晶发生。基于热变形动力学模型建立了本构方程,表观应力指数为3.99,热变形激活能为393.75kJ/mol。S32750的高温软化机制与Zener-Hollomon(Z)参数有关,随Z参数增加,热变形峰值应力增加。     

Ti-Al-Nb-W基合金高温变形过程中的组织演化

在Thermecmastor-Z动态热模拟试验机上对Ti-43Al-4Nb-1.4W和Ti-43Al-4Nb-1.4W-0.6B-0.2Y合金进行高温压缩变形实验(实验温度范围为1 050~1 150℃,应变速率范围为0.001~1 s 1),对其热变形组织进行显微分析,并利用热加工Z参数(Zener-Hollomon参数)综合描述变形温度及应变速率对材料热变形行为的影响。结果表明:2种合金在不同高温压缩变形条件下均发生不同程度的动态再结晶;随Z参数值的降低,β相逐渐由不规则形状转变为球形,且长大明显,同时,动态再结晶晶粒的体积含量也随之增加;Ti-43Al-4Nb-1.4W基合金的高温变形机制与Z参数值密切相关;在低Z值条件下,其主要变形机制为动态再结晶和β相的球化、长大;在高Z值条件下,其主要变形机制为片层的扭折、重新取向和局部动态再结晶;加入微量B和Y后,动态再结晶程度增大,这主要与颗粒诱发动态再结晶形核有关。     

HGH3126镍基合金热变形行为及组织演变

通过热压缩实验研究了HGH3126镍基合金（/%:≤0.005C,17.20Cr,4.21W,16.25Mo,5.49Fe,0.46Mn,0.20V）在变形温度为950～1200℃、应变速率为0.01～10 s^-1的热变形行为。基于Arrhenius方程和Zener-Hollomon参数模型,建立了HGH3126合金高温热变形的流变应力本构方程。通过对高温热变形后的HGH3126合金显微组织进行观察,分析了变形温度和应变速率对HGH3126合金动态再结晶行为的影响。结果表明,变形温度越高,合金动态再结晶越容易形核;应变速率越小,合金动态再结晶过程进行得越充分。当应变速率0.1 s^-1,变形温度1100℃时,该合金基本发生完全动态再结晶。     

Hot Deformation Behavior of Modified CNS-Ⅱ F/M Steel

 Modified CNS-Ⅱ F/M steel was designed for in-core components of supercritical water cooled reactor. Study on the hot deformation behavior of modified CNS-Ⅱ F/M steel is of great importance for processing parameter planning and microstructure controlling during hot deformation. The hot deformation behavior of modified CNS-Ⅱ F/M steel was investigated through isothermal hot compression test at temperature ranging from 1223 to 1373 K and strain rate 001 to 10 s-1. The true stress-true strain data gained from compression tests were used to built constitutive equation of modified CNS-Ⅱ F/M steel. The influence of strain on the accuracy of constitutive analysis was incorporated, assuming strain has a influence on material constants. A 5th order polynominal equation with very good accuracy was used to represent the influence of strain on material constant. The flow stresses calculated from the constitutive equation were compared with test values in the whole experiment range and the absolute average error for the constitutive equation in predicting flow stress is 4728%. At last, the recrystallization behavior of modified CNS-Ⅱ F/M steel was investigated. The relationship of critical strain and peak strain with Zener-Hollomon parameter were given by an experimental equation.     

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.     

Hot deformation behavior of 07Cr25Ni21NbN austenitic heat resistant steel modified using 0. 3% vanadium

Hot deformation behavior and processing maps of test steel were investigated at temperature range of 930-1230?? and the strain rate range of 0. 005-5s-1using isothermal hot compression tests by Gleeble3800 thermal- mechanical simulators. The change of microstructure of test steel with different deformation conditions was observed by means of metallographic microscope. The flow stress curve of the test steel was analyzed and its activation energy for thermal deformation was 571kJ/mol. The processing maps of the test steel were established when the true strain were 0. 4 and 0. 8, respectively. It is found that there are three boundaries of the peak area of dissipation power in processing map with the true strain of 0. 8. When the deformation temperature is 1230?? and the deformation rate is from 0. 005 to 5s-1, the microstructure of the test steel transitions from coarse serrated grains to finer equiaxed grains. When the deformation rate is 0. 5s-1 and the deformation temperature is increased from 930?? to 1230??, the microstructure changes from equiaxed structure and partially dynamic recrystallization structure to flow instability structure.     

片层组织TC17钛合金高温变形行为研究

通过热压缩试验研究了具有初始片层组织的TC17钛合金在780~860℃和应变速率0.001~10 s-1范围内的热变形行为和组织演变。分析了该合金在两相区变形的应力-应变曲线特征,其流变应力本构关系可以用双曲正弦方程和Zener-Hollomon参数描述,得到TC17合金在两相区变形的平均激活能为488.86 kJ.mol-1。显微组织分析发现:TC17合金在两相区变形时组织演变的主要特征是片层组织球化;热变形参数严重影响片层组织球化过程的进行,加大变形量、降低应变速率以及提高变形温度可以提高片状组织的动态球化程度。     

F40MnV非调质钢的热变形行为

 采用Gleeble 1500热模拟实验机对F40MnV非调质钢在温度为1 223~1 473 K，应变速率为01~10 s-1的热变形行为进行研究。通过奥氏体再结晶动力学回归计算得到了F40MnV钢的变形激活能，峰值应力和峰值应变与Zener Hollomon参数的关系表达式。同时，得到了F40MnV钢的动态再结晶动力学方程和动态再结晶晶粒尺寸的数学模型。     

RAFM钢应变补偿本构关系及热加工图

 低活化铁素体/马氏体(RAFM)钢具有较低的辐照肿胀率和优异的力学性能,被认为是聚变堆首选的结构材料。然而,低活化钢强度高、冷塑性变形抗力大的特点,使其难以通过冷加工或低温加工实现大规模生产。使用MMS-200型热模拟试验机,在变形温度为950~1 200 ℃、应变速率为0.1~5 s-1和最大变形量为50%条件下,进行了低活化铁素体/马氏体钢(0.11C-9.4Cr-1.35W-0.22V-0.05Si-0.11Ta-0.50Mn)单道次热压缩试验,研究其热变形行为。基于动态材料模型构建了不同应变量下的低活化钢变形本构方程和热加工图,确定了最优热加工参数,结合金相结果分析了材料变形过程中微观组织演化规律,为低活化钢的热加工成形工艺及组织优化提供理论参考。结果表明,在相同应变速率下,随着变形温度升高,流变应力逐渐降低,在一定变形温度下,流变应力随应变速率增大而增大;温度和应变速率对组织的影响主要取决于变形过程中材料内部发生的动态回复和再结晶等机制的交互作用。使用六阶多项式拟合进行应变补偿建立的低活化钢变形本构方程具有较高的预测精度,平方相关系数为0.972。显微组织和热加工图分析结果表明,温度升高为再结晶提供了充足能量,材料软化机制由动态回复转变为动态再结晶;减小应变速率,能量有足够时间扩散,有利于动态再结晶的进行;在变形温度为1 060~1 130 ℃、应变速率为0.13~0.36 s-1条件下和合金耗散系数η达到36%的最佳热加工参数范围,可获取到均匀动态再结晶组织。     

0.03Nb-0.15Ti微合金化低碳高强度钢的动态再结晶

通过Gleeble 1500热模拟试验机试验研究了Nb-Ti微合金化低碳钢（/%:0.06C,0.22Si,1.80Mn,0.03Nb,0.15Ti,≤0.007N,≤0.002S）10mm带钢在850~1100℃,以应变速率0.1~20.0 s^-1,总变形量75%单道次压缩变形时动态再结晶,由真应力-真应变曲线,结合加工硬化率曲线,得出动态再结晶临界应变0.4~0.7和完全再结晶应变量1.1~1.4。该钢的热变形激活能为618.225 kJ/mol。根据试验结果得到Zener-Hollomon方程和动态再结晶状态图,利用Johnson-Mehl-Avrami（JMA）方程法得到再结晶体积分数实际值,采用Epsilon-P模型对实验数据进行回归,得到试验钢的再结晶动力学模型。     

T91钢的高温塑性变形及动态再结晶行为

采用Gleeble-1500热模拟试验机进行了T91钢的压缩试验,研究了变形温度为1100~1250℃、应变速率为0.01~1 s-1时该钢的变形行为,分析了流变应力与应变速率和变形温度之间的关系,计算了高温变形时应力指数和变形激活能,并采用Zener-Hollomon参数法构建该钢高温塑性变形的本构关系,绘制了动态再结晶图和热加工图.结果表明:在试验变形条件范围内,其真应力-真应变曲线呈双峰特征;钢中发生了明显的动态再结晶,且再结晶类型属于连续动态再结晶.T91钢的热变形激活能为484 kJ.mol-1,利用加工图确定了热变形的流变失稳区,结合力学性能,可以优先选择的变形温度为1200~1 250℃,应变速率不高于0.1 s-1.