Mg-9Gd-3Y合金热变形行为与本构关系

为了解决Mg-9Gd-3Y合金在热塑性变形过程中的本构关系问题,对Mg-9Gd-3Y合金进行了不同变形温度（653～753K）下采用不同应变速率（0.01～10s-1）的热压缩试验,利用载荷/位移数据建立真应力/真应变曲线和本构方程.结果表明：动态再结晶在晶界处较易发生,流变曲线显示出典型的动态再结晶特征,以及应力水平与变形温度和应变速率的关系.本构方程预测出的流变应力数据与相应的试验结果较一致.     

Flow stress behavior and processing map of Al-Cu-Mg-Ag alloy during hot compression

The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.     

Constitutive analysis of AZ31 magnesium alloy plate

The plastic deformation simulation of AZ31 magnesium alloy at different elevated temperatures (from 473 to 723 K) was performed on Gleeble-1500 thermal mechanical simulator at the strain rates of 0.01, 0.1, 1, 5 and 10 s-1 and the maximum deformation degree of 80%. The relationship between the flow stress and deformation temperature as well as strain rate was analyzed. The materials parameters and the apparent activation energy were calculated. The constitutive relationship was established with a Zener-Holl...     

AZ81E镁合金的高温流变应力模型及热加工图研究

在应变速率为0．003—3．0s^-1、温度为340～430℃的变形条件下,采用Gleeble-1500热模拟机对AZ81E镁合金进行高温热压缩变形特性研究。结果表明：流变应力随变形温度的升高和应变速率的降低而减小,峰值应力随温度的降低和应变速率的升高向应变较大处转移,进入稳态阶段的临界应变明显增大。结合Arrhenius方程并引入Zener-Hollomon参数,构建AZ81E镁合金的高温流变应力模型,其平均变形激活能为166．15kJ／mol。根据材料动态模型,计算并分析AZ81E镁合金的热加工图。利用热加工图确定热变形的流变失稳区,获得试验参数范围内的热变形过程最佳工艺参数：热加工温度范围为380～420℃,应变速率范围为0．01～0．03S^-1.     

Effect of twinning on flow stress during initial stage of hot compression of twin roll cast Mg-5.51Zn-0.49Zr alloy

A Thermecmastor-Z hot deformation simulator,optical microscopy,XRD and TEM were employed to characterize the flow stress behavior and microstructure of twin roll cast ZK60 magnesium alloy during initial stage of hot compression at elevated temperature of 300 ℃ and 400 ℃ and a given strain rate of 10-2s-1.The results suggest that flow stress drop during initial stage of hot compression at 300℃,generally led by dynamic recrystallization,is attributed to twinning,correspondingly to dynamic recrystallization as...     

37Mn5钢热变形行为与流变应力模型研究

利用Gleeble-1500热模拟实验机研究37Mn5钢在变形温度为800～1150℃、变形速率为0．1～10s^-1条件下的热压缩变形行为。采用应变硬化率-应力曲线图较精确地获得峰值应力,并用双曲正弦方程描述37Mn5钢热压缩变形过程中的峰值应力与Zener—Hollomon参数的关系。回归分析得到方程中变形激活能及各材料常数的值,获得37Mn5钢在高温条件下的流变应力本构方程。结果表明,采用该本构方程计算出的流变应力值与实验所得应力值非常接近。     

Al-Mg-Si合金热压缩变形的流变应力方程

为了给制定和优化热加工工艺参数提供理论依据,采用Gleeble-1500热模拟机研究了含锆Al-Mg-Si合金在变形温度为653~803 K、变形速率为0.01~10s^-1条件下的热压缩变形的流变应力行为,并通过回归法建立材料变形的流变应力数学模型.结果表明：该合金为正应变速率敏感材料,真应力-真应变曲线存在明显的稳态流变特征;流变应力随着变形速率的增加以及变形温度的降低而增加;在较低变形温度条件下,真应力〖CDF*3〗真应变曲线为动态回复曲线;在较高变形温度条件下真应力-真应变曲线为动态再结晶曲线.该合金流变应力σ可用包含Arrhenius项的Zener Hollomon参数的函数来描述,式中A、α和n的值分别为1.89×10¹⁰s^-1、0.024MPa^-1和7.46,热变形激活能Q为166.85kJ/mol.     

Hot deformation behaviors and flow stress model of GCr15 bearing steel

The hot deformation behaviors of GCr15 bearing steel were investigated by isothermal compression tests, performed on a Gleeble-3800 thermal-mechanical simulator at temperatures between 950℃ and 1150℃ and strain rates between 0.1 and 10 s^-1. The peak stress and peak strain as functions of processing parameters were obtained. The dependence of peak stress on strain rate and temperature obeys a hyperbolic sine equation with a Zener-Hollomon parameter. By regression analysis, in the temperature range of 950-1 150℃ and strain rate range of 0.1-10 s^-1, the mean activation energy and the stress exponent were determined to be 351kJ/mol and 4.728, respectively. Meanwhile, models of flow stress and dynamic recrystallization （DRX） grain size were also established. The model predictions show good agreement with experimental results.     

Constitutive Modeling and Dynamic Recrystallization Mechanisms of an Ultralow-carbon Microalloyed Steel During Hot Compression Tests

The hot deformation behavior of an ultralow-carbon microalloyed steel was investigated using an MMS-200 thermal simulation test machine in a temperature range of 1 073-1 373 K and strain rate range of 0.01-10 s~(-1).The results show that the flow stress decreases with increasing deformation temperature or decreasing strain rate.The strain-compensated constitutive model based on the Arrhenius equation for this steel was established using the true stress-strain data obtained from a hot compression test.Furthermore,a new constitutive model based on the Z-parameter was proposed for this steel.The predictive ability of two constitutive models was compared with statistical measures.The results indicate the new constitutive model based on the Z-parameter can more accurately predict the flow stress of an ultralow-carbon microalloyed steel during hot deformation.The dynamic recrystallization (DRX) nucleation mechanism at different deformation temperatures was observed and analyzed by transmission electron microscopy (TEM),and strain-induced grain boundary migration was observed at 1 373 K/0.01 s~(-1).     

Hot deformation behavior of Super304H austenitic heat resistant steel

The hot compression tests of Super304H austenitic heat resistant steel were carried out at 800-1200℃and 0.005-5 s~(-1) using a Gleeble 3500 thermal-mechanical simulator,and its deformation behavior was analyzed.The results show that the flow stress of Super304H steel decreases with the decrease of strain rate and the increase of deformation temperature;the hot deformation activation energy of the steel is 485 kJ/mol.The hot deformation equation and the relationship between the peak stress and the deforma...     

Flow stress behavior and constitutive modeling of 20MnNiMo low carbon alloy

The hot deformation behavior of 20 Mn Ni Mo low carbon alloy was investigated by isothermal compression tests over wide ranges of temperature(1223-1523 K) and strain rate(0.01-10 s~(-1)). According to the experimental true stress-true strain data, the constitutive relationships were comparatively studied based on the Arrhenius-type model, Johnson-Cook(JC) model and artificial neural network(ANN), respectively. Furthermore, the predictability of the developed models was evaluated by calculating the correlation coefficient(R) and mean absolute relative error(AARE). The results indicate that the flow stress behavior of 20 Mn NiM o low carbon alloy is significantly influenced by the strain rate and deformation temperature. Compared with the Arrhenius-type model and Johnson-Cook(JC) model, the ANN model is more efficient and has much higher accuracy in describing the flow stress behavior during hot compressing deformation for 20 Mn Ni Mo low carbon alloy.     

碳化硅颗粒增强6168铝基复合材料热变形本构关系

利用Gleeble-3500热模拟试验机研究碳化硅颗粒增强6168铝基复合材料(SiCp/6168Al)在变形温度为340~540 ℃、应变速率为0.001~10 s-1、真应变为0.7的条件下的热变形行为。结果表明:应变速率和变形温度对流变应力有明显的影响,在应变速率相同的条件下,流变应力随变形温度的升高而降低,相同的变形温度下,随应变速率的增加,流变应力也随之升高。采用双曲正弦模型求解SiCp/6168Al复合材料在不同真应变ε下的材料常数,并使用5次指数函数拟合出n、lnA、α和Q与真应变ε的关系式,建立流变应力σ与真应变ε的本构方程。利用该方程可以计算任意变形条件下的流变应力,该模型能较好地反映该复合材料的实际热变形行为。       

Hot Deformation Kinetics of Magnesium Alloy AZ31

1 IntroductionManyirreplaceable characteristics andthe abundanceof magnesiumalloyin nature have drawn a world wide at-tentionin 21st century.In contrast with the cast magne-siumalloy,wrought magnesiumalloyis much betterinitscomprehensive mechanical properties ,so a wide applica-tionis found in many fields like transportation,aeronau-tics ,electricity and communication.The flowstress of a material depends upontwo majorfactors ,namely,its own characteristics and its deforma-tionterms .The basic …     

Prediction of 2A70 aluminum alloy flow stress based on BP artificial neural network

Recently ,withtherapiddevelopmentofthecompu tationtechnique ,thefiniteelementmethodisappliedmoreandmoretothenumericalsimulationofthemetalformingprocess .Therelationshipbetweenflowstressanddeformationconditionssuchasstrain ,strainratesandtemperatures,whichembodiestheresponseofamaterialtothedeformationparameters ,isveryimportantforthenumericalsimulationbyfiniteelementmethod .Butduringthehotdeformationprocess ,therearemanyfactorsthatinfluencetheflowstressofthemetal .Theeffectsofthesefactorsonthef…     

Microstructure and flow stress of Mg-12Gd-3Y-0.5Zr magnesium alloy

The microstructure and flow stress of the Mg-12Gd-3Y-0.5Zr magnesium alloy was investigated by compression test at temperatures ranging from 350 to 500 ℃ and the strain rates ranging from 0.01 to 20 s-1. The flow stress of the magnesium alloy increased with strain rate and decreased with deformation temperature. Flow stress can be expressed in terms of the Zener-Hollomon parameter Z, which describes the combined influence of the strain rate and temperature using an Arrhenius function.The values of the deformation activation energy were estimated to be 245.9 and 171.5 kJ/mol at deformation temperatures below 400 ℃ and above 400 ℃, respectively. Two constitutive equations were developed to quantify the effect of the deformation conditions on the flow stress of the magnesium alloy. The effects of deformation temperature and strain rate on the microstructure of the magnesium alloy were also examined and quantified by measuring the volume fraction of dynamically recrystallized grain Xd. Xd increased with increasing of deformation temperature. When the deformation temperature was below 475 ℃, Xd decreased with strain rate until it reached 0.15 s-1, then it increased again. When the deformation temperature was above 475 ℃, Xd increased with strain rate.     

TC6钛合金高温变形本构方程的建立

通过Gleeble-3500热模拟实验机获得了TC6钛合金在变形温度为800~980℃,应变速率为0.5~5s-1,变形程度为30%和60%时的应力-应变曲线。利用高温变形机理分析了热变形参数对流动应力的影响规律,建立了可用于锻造过程数值模拟的TC6合金高温变形的本构方程。     

热压缩铝合金LY12流变应力的影响因素分析

采用Ｇｌｅｅｂｌｅ－１５００热力模拟机高温等温压缩实验,研究了铝合金ＬＹ１２高温塑性变形时的流变应力行为,研究结果表明,应变速率和变形温度的变化明显影响合金稳态流变应力的大小,且变形温度、应变速率、变形程序对流变应力也有一定的影响。     

温度和应变速率对ZK60镁合金压缩变形行为的影响

在应变量为0.6（ε=0.6）、不同温度（523~723 K）和应变速率（0.001~10 s-1）条件下,利用Gleeble-1500D热模拟试验机,对铸态ZK60镁合金进行热压缩变形行为的研究,分析变形温度和应变速率对ZK60镁合金压缩变形行为的影响规律,即在相同应变速率条件下,随着变形温度的升高,合金的峰值应力降低。在相同温度条件下,随着应变速率的增大,合金的流变应力增大。计算其应变速率敏感指数m值为0.14和表观激活能Q值为226~254 kJ/mol。研究表明,在温度为573~673 K、应变速率为0.001~0.1 s-1时,合金发生动态再结晶。     

TC4钛合金在不同温度下的剪压缩失效

利用Fallwerk试验装置,在高应变率(102s-1)下,采用动态剪压缩试验研究TC4钛合金不同温度下的剪压缩失效现象。通过试验发现:相同温度下,流变应力随应变的增大不断增加,到达峰值后发生应力塌陷,即剪切失效;相同应变下,温度越高,材料的屈服强度和流变应力均明显下降,且峰值应力向应变增大的方向移动,即塑性变形能力逐渐加强;温度升高,材料的剪切失效能力减弱,在673 K至873 K温度区间内存在一个温度极限值。在该极限值以下,材料易发生剪切失效。同时,根据试验数据拟合了峰值应力和最大塑性应变与温度的曲线方程,为钛合金的研究提供了理论依据。     

7055铝合金高温压缩变形的流变应力

在Gleeble 1500热模拟试验机上,采用高温等温压缩试验,研究了7055铝合金在250～450℃温度范围内压缩变形的流变应力变化规律.结果表明,应变速率和变形温度的变化强烈影响合金的流变应力,流变应力随变形速率的提高而增大;随变形温度的提高而降低.7055铝合金高温变形时的流变应力可用Zener Hollomon参数来描述.