Mg-10Gd-4.8Y-2Zn-0.6Zr合金本构方程模型及加工图

采用Gleeble-1500热模拟实验机在温度为623～773K,应变速率为0.001～1s-1条件下对Mg-10Gd-4.8Y-2Zn-0.6Zr(wt%)合金进行热压缩实验,研究了该合金热变形行为及热加工特征,建立了该合金热变形时的本构方程和加工图.结果表明,该合金高温变形时的峰值应力随着应变速率的降低和变形温度的升高而显著减小;变形激活能为289.36kJ/mol;合金高温变形时存在两个失稳区,分别是变形温度为770～773K,应变速率为0.1s-1左右的区域,和变形温度小于750K,应变速率小于0.03s-1的区域;合金的最佳热加工温度为750～773K,应变速率为0.001～0.01s-1.     

锌合金高温变形行为及加工图

在Gleeble-1500D热模拟机上采用等温压缩实验研究Zn-8Cu-0.3Ti锌合金的高温流变行为,获得锌合金在变形温度为230～380℃、应变速率为0.01～10 s-1和变形程度为50%条件下的真应力—应变曲线,根据动态材料模型(DMM)建立锌合金的热加工图。结果表明:Zn-8Cu-0.3Ti锌合金在实验条件下具有正的应变速率敏感性,流变应力随着应变速率的增大而增大,随着变形温度的升高而减小,该合金的流变应力行为可用Arrhenius方程来描述。在本研究条件下,Zn-8Cu-0.3Ti锌合金在热变形时存在一个失稳区,即应变速率0.2 s-1以上的区域;在应变速率小于0.001 s-1和340～370℃温度范围内,最大功率耗散系数为0.53,该安全区域内合金的变形机制为动态再结晶。     

高温环境下Mg-Zn-Zr-Ce合金的变形行为研究

研究了Mg-6Zn-0.5Zr-0.5Ce镁合金的显微结构和热变形行为,并构建了该合金的热加工图。结果表明,铸态和退火态Mg-6Zn-0.5Zr-0.5Ce镁合金主要由α-Mg基体和分布在晶界和晶粒内部的第二相构成。随着真应变的不断变大,流变应力先变大后下降,并逐渐趋于平稳。加工失稳区位于ε=0.1¹.0 s-1,T=5231.0 s-1,T=523⁵73 K区域,ε=1.0 s-1,T=673 K,η=44%是Mg-6Zn-0.5Zr-0.5Ce镁合金最佳的加工条件。     

Al-Zn-Mg-Sc-Zr合金的热变形行为及加工图

在Gleeble-1500热模拟试验机上对Al-5.5Zn-1.5Mg-0.2Sc-0.1Zr铝合金进行高温等温压缩实验,研究该合金在变形温度为300～500℃、应变速率为0.01～10s-1条件下的流变行为,建立合金高温变形的本构方程和加工图,采用电子背散射衍射(EBSD)分析变形过程中合金的组织特征.结果表明流变应力随变形温度的升高而降低;当应变速率ε=10s-1,变形温度为300～500℃时,合金发生了动态再结晶.Al-5.5Zn-1.5Mg-0.2Sc-0.1Zr合金的高温流变行为可用Zener-Hollomon参数描述.在热变形过程中,随着真应变增加,合金的变形失稳区域增大.该合金适宜的变形条件如下变形温度300～360℃、应变速率0.01～0.32s-1,或变形温度380～500℃、应变速率0.56～10s-1.     

铸态Mg-8Zn-1Al-0.5Cu-0.5Mn镁合金的热变形行为和热加工图（英文）

采用热压缩实验研究Mg-8Zn-1Al-0.5Cu-0.5Mn镁合金在温度为200~350°C、应变速率为0.001~1 s-1条件下的热变形行为。结果表明,流变应力随着应变速率的增加而明显增大,随着变形温度的升高而减小。同时,采用回归分析的方法建立预测合金流变应力的模型,该模型与实验结果能较好地吻合。以动态材料模型为基础建立合金的热加工图,从加工图中可以看出,随着应变的增大,合金的非稳态区域变大,合金在高温和低应变速率下具有良好的加工性。     

Mg-6Zn-1Mn镁合金的热压缩变形行为及加工图

采用Gleeble-1500热/力模拟试验机进行压缩试验,研究了Mg-6Zn-1Mn合金在变形温度250～450℃、应变速率0.001～10 s-1范围内的流变应力行为,采用Zener-Hollomon参数法构建合金高温塑性变形的本构关系;并以热压缩试验为基础,建立并初步分析了Mg-6Zn-1Mn合金的DMM加工图。结果表明:Mg-6Zn-1Mn合金在热压缩过程中发生了明显的动态回复与动态再结晶,流变应力随应变速率的增加而增加,随温度的升高而降低;流变应力的预测值与试验值较吻合;建立的加工图表明合金高温变形时存在2个失稳区域,而在温度325～425℃、应变速率0.01～0.365 s-1范围内出现1个非失稳区、功率耗散峰值区,该区域最适合Mg-6Zn-1Mn合金进行热加工。     

超细晶不锈钢/TiC复合材料的电化学腐蚀行为

采用Gleeble-1500热/力模拟试验机进行压缩试验,研究了Mg-6Zn-1Mn合金在变形温度250～450℃、应变速率0.001～10 s-1范围内的流变应力行为,采用Zener-Hollomon参数法构建合金高温塑性变形的本构关系;并以热压缩试验为基础,建立并初步分析了Mg-6Zn-1Mn合金的DMM加工图.结果表明:Mg-6Zn-1Mn合金在热压缩过程中发生了明显的动态回复与动态再结晶,流变应力随应变速率的增加而增加,随温度的升高而降低;流变应力的预测值与试验值较吻合;建立的加工图表明合金高温变形时存在2个失稳区域,而在温度325～425℃、应变速率0.01～0.365 s-1范围内出现1个非失稳区、功率耗散峰值区,该区域最适合Mg-6Zn-1Mn合金进行热加工.     

Al-6Zn-2Mg-0.2Sc-0.1Zr合金的热变形工艺研究

在Gleeble-1500热模拟实验机上对Al-6Zn-2Mg-0.2Sc-0.1Zr合金进行等温压缩试验,建立了该合金在变形温度为350～500℃、应变速率为1～10 s-1条件下的热加工图。利用光学显微镜和扫描电镜观察了不同变形程度下合金的组织和热裂纹,确定了适宜的变形参数。结果表明:Al-6Zn-2Mg-0.2Sc-0.1Zr合金高温变形的峰值应力随变形温度的升高而降低,其适宜的热加工温度和应变速率范围为:T440℃,1.4 s-1ε3.5 s-1,单道次变形量小于60%。     

粗晶Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr合金高温变形行为

采用Gleeble-1500热模拟机研究粗晶Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr镁合金在温度为623～803 K、应变速率为0.005～5 s-1条件下的高温变形行为。结果表明:流动应力随变形温度的降低或应变速率的升高而增加,在高温变形初始阶段,流动应力随应变的增加迅速增加,当应变超过一定值后,流变应力开始下降并逐渐趋于稳定,出现稳态流动特征;基于Arrhenius方程建立Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr合金高温流变应力本构模型;在723 K、应变速率0.05 s-1条件下,显微组织出现大晶粒被细小晶粒包围的"项链"组织特征,局部晶粒交结处出现微裂纹与孔洞;根据实验结果,合金的热加工宜在773 K左右进行。     

Mg-3.5Zn-0.6Y-0.5Zr合金高温压缩变形行为

采用Gleeble-1500D热模拟实验机,研究了Mg-3.5Zn-0.6Y-0.5Zr合金在变形温度为300~450℃、变形速率为0.002~1s-1及变形量为50%的条件下的高温压缩变形行为,分析了流变应力与应变速率、变形温度的关系,计算了高温变形时变形激活能和应力指数,建立了该合金的本构方程。结果表明:Mg-3.5Zn-0.6Y-0.5Zr合金在热变形过程中真应力随着温度的升高而降低,真应力随着应变速率的升高而升高。该合金的流动应力可以用双曲正弦函数来描述。     

Strain-dependent constitutive analysis of hot deformation and hot workability of T4-treated ZK60 magnesium alloy

The hot deformation behavior of T4-treated ZK60 magnesium alloy was investigated in a compression test conducted with a thermo-mechanical simulator at a temperature range of 523 K to 673 K and a strain rate of 0.001 s^?1 to 1 s^?1. The results show that the flow stress increases as the deformation temperature decreases and the strain rate increases. Strain-dependent constitutive relationships were developed using regression method and artificial neural network, and good agreements between the experimentally measured values and the predicted ones were achieved. The work hardening analysis and onset of dynamic recrystallization (DRX) were investigated. The processing map reveals a domain of DRX at the temperature range of 620–673 K and strain rate range of 0.001–0.01 s^?1, with its peak efficiency of 32% at 623 K and 0.001 s^?1, which are the optimum values of the parameters for hot working of the T4-treated ZK60 alloy. The strain level has a great effect on the processing maps and lower temperatures and higher strain rates should be avoided during hot working processes. DRX model indicates that DRX of ZK60 alloy is controlled by the rate of nucleation, which is slower than the rate of migration.     

Flow behavior of Al–6.2Zn–0.70Mg–0.30Mn–0.17Zr alloy during hot compressive deformation based on Arrhenius and ANN models

The hot deformation behavior of Al–6.2Zn–0.70Mg–0.30Mn–0.17Zr alloy was investigated by isothermal compression test on a Gleeble–3500 machine in the deformation temperature range between 623 and 773 K and the strain rate range between 0.01 and 20 s^?1. The results show that the flow stress decreases with decreasing strain rate and increasing deformation temperature. Based on the experimental results, Arrhenius constitutive equations and artificial neural network (ANN) model were established to investigate the flow behavior of the alloy. The calculated results show that the influence of strain on material constants can be represented by a 6th-order polynomial function. The ANN model with 16 neurons in hidden layer possesses perfect performance prediction of the flow stress. The predictabilities of the two established models are different. The errors of results calculated by ANN model were more centralized and the mean absolute error corresponding to Arrhenius constitutive equations and ANN model are 3.49% and 1.03%, respectively. In predicting the flow stress of experimental aluminum alloy, the ANN model has a better predictability and greater efficiency than Arrhenius constitutive equations.     

Effect of Zener–Hollomon Parameter on High-Temperature Deformation Behaviors of Mg–6Zn–1.5Y–0.5Ce–0.4Zr Alloy

High-temperature compressive deformation behaviors of Mg–6Zn–1.5Y–0.5Ce–0.4Zr alloy were investigated at temperatures and strain rates ranging from 523 to 673 K and from 0.001 to 1 s~(-1),respectively.The studied alloy was mainly composed ofα-Mg,Mg _(3 )Zn _(6 )Y (I phase),Mg–Zn–Ce and Mg _(3 )Zn _(3 )Y _(2 )(W phase).The constitutive equation of Mg alloy was obtained,and the apparent activation energy (Q) was determined as 200.44 k J/mol,indicating that rare earth phase increases the difficulty of deformation.The work hardening involves three stages:(1) linear hardening stage;(2) strain hardening stage;and (3)softening and steady-state stage.During these three stages,the dislocation aggregation and tangling,dynamic recovery and recrystallization occur sequentially.To characterize the dynamic recrystallization (DRX) volume fraction,the DRX kinetics was investigated using the Avrami-type equation.The deformation mechanism of magnesium alloy under different Zener–Hollomon parameter (Z) value conditions was also studied.At high Z values and intermediate conditions,dislocations rapidly generate and pile up in the alloy.Recrystallization is hardly seen at this time.At low Z condition,the DRX occurs in the alloy.     

Cu-Ni-Si-P合金热变形行为及热加工图

采用高温等温压缩试验,对Cu?Ni?Si?P合金在应变速率0.01~5?1、变形温度600~800°C条件下的高温变形行为进行了研究,得出了该合金热压缩变形时的热变形激活能Q和本构方程。根据实验数据与热加工工艺参数构建了该合金的热加工图,利用热加工图对该合金在热变形过程中的热变形工艺参数进行了优化,并利用热加工图分析了该合金的高温组织变化。热变形过程中Cu?Ni?Si?P合金的流变应力随着变形温度的升高而降低,随着应变速率的提高而增大,该合金的动态再结晶温度为700°C。该合金热变形过程中的热变形激活能Q为485.6 kJ/mol。通过分析合金在应变为0.3和0.5时的热加工图得出该合金的安全加工区域的温度为750~800°C,应变速率为0.01~0.1 s?1。通过合金热变形过程中高温显微组织的观察,其组织规律很好地符合热加工图所预测的组织规律。     

Microstructural evolution,flow stress and constitutive modeling of Al−1.88Mg−0.18Sc−0.084Er alloy during hot compression

To explore the hot compression behavior and microstructural evolution, fine-grained Al?1.88Mg?0.18Sc? 0.084Er (wt.%) aluminum alloy wires were fabricated with Castex (continuous casting?extrusion) and ECAP-Conform, and their hot compression behavior was investigated at temperatures of 673?793 K and strain rates of 0.001?10 s^?1; the microstructures were characterized by optical microscope, X-ray diffractometer, transmission electron microscope, and electron backscattered diffractometer, and the flow stresses were obtained by thermal compression simulator. Microstructural evolution and flow curves reveal that dynamic recovery is the dominant softening mechanism. Continuous dynamic recrystallization followed by dynamic grain growth takes place at a temperature of 773 K and a strain rate of 0.001 s^?1; the yielding drop phenomenon was discovered. Hyperbolic sine constitutive equation incorporating dislocation variables was presented, and a power law constitutive equation was established. The stress exponent is 3.262, and the activation energy for deformation is 154.465 kJ/mol, indicating that dislocation viscous glide is the dominant deformation mechanism.     

Microstructure characterization of Al-cladded Al–Zn–Mg–Cu sheet in different hot deformation conditions

Al-cladded Al–Zn–Mg–Cu sheets were compressed up to 70% reduction on a Gleeble–3500 thermo-mechanical simulator with temperatures ranging from 380 to 450 °C at strain rates between 0.1 and 30 s^?1. The microstructures of the Al cladding and the Al–Zn–Mg–Cu matrix were characterized by electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). The microstructure is closely related to the level of recovery and recrystallization, which can be influenced by deformation temperature, deformation pass and deformation rate. The level of recovery and recrystallization are different in the Al cladding and the Al–Zn–Mg–Cu matrix. Higher deformation temperature results in higher degree of recrystallization and coarser grain size. Static recrystallization and recovery can happen during the interval of deformation passes. Higher strain rate leads to finer sub-grains at strain rate below 10 s^?1; however, dynamic recovery and recrystallization are limited at strain rate of 30 s^?1 due to shorter duration at elevated temperatures.     

Microstructure evolution and hot deformation behavior of Cu−3Ti−0.1Zr alloy with ultra-high strength

The hot compression deformation behavior of Cu–3Ti–0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble–3500 thermal-mechanical simulator at temperatures from 700 to 850 °C with the strain rates between 0.001 and 1 s⁻¹. The results show that work hardening, dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation. The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol. The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result, and the hot processing maps are established based on the dynamic material model. The optimal hot deformation temperature range is between 775 and 850 °C and the strain rate range is between 0.001 and 0.01 s⁻¹.     

Microstructure and mechanical properties of Mg–Zn–(Nd)–Zr alloys with different extrusion processes

The effect of Nd addition and the in?uence of extrusion processes on the microstructure and mechanical properties of Mg–6Zn–0.5Zr(ZK60) and Mg–6Zn–1.5Nd–0.5Zr(ZKNd602) alloys were investigated. Nd element can obviously re?ne the microstructure of both as-cast and asextruded Mg–Zn–Nd–Zr alloy. All of the extruded alloys exhibit a bimodal grain structure composed of equiaxed?ne recrystallized(DRXed) grains and elongated coarse un DRXed grains. It is necessary to achieve high strength,particularly the yield strength, for ZKNd602 alloy, when it is extruded with a lower extrusion temperature, a suitable extrusion ratio and a relatively lower extrusion ram speed. In this study, the ultimate tensile strength(UTS),yield strength(YS) and elongation(El) of the extruded ZKNd602 alloy were 421 MPa, 402 MPa and 6.7 %,respectively, with extrusion temperature of 290 °C, extrusion ratio of 18:1 and a ram speed of approximate0.4 mm·s~(-1). Meanwhile, the extrusion process has obvious effects on the room-temperature properties but weak effects on the high-temperature properties.     

轧制态ME20M镁合金热拉伸变形行为及加工图

在变形温度为623～773 K,应变速率为0.001～0.1 s~(-1)的条件下,通过INSPEKT Table 100 kN电子万能高温试验机对轧制态ME20M镁合金进行了热拉伸实验,分析了变形温度和应变速率对材料流动应力的影响,建立了热变形条件下的本构模型及加工图。结果表明:随着变形温度的降低和应变速率的升高,轧制态ME20M镁合金的流动应力增加;建立的本构模型预测峰值应力与实验结果吻合较好,平均相对误差为5.19%;考虑应变对本构模型中材料常数影响后的预测应力值与实验值的相关度较高,平均相对误差为6.00%;最佳热加工范围为673～773 K、应变速率0.001～0.01 s~(-1)。     

Role of activation energies of individual phases in two-phase range on constitutive equation of Zr–2.5Nb–0.5Cu alloy

Dominant phase during hot deformation in the two-phase region of Zr–2.5Nb–0.5Cu (ZNC) alloy was studied using activation energy calculation of individual phases. Thermo-mechanical compression tests were performed on a two-phase ZNC alloy in the temperature range of 700–925 °C and strain rate range of 10^?2–10 s^?1. Flow stress data of the single phase were extrapolated in the two-phase range to calculate flow stress data of individual phases. Activation energies of individual phases were then calculated using calculated flow stress data in the two-phase range. Comparison of activation energies revealed that α phase is the dominant phase (deformation controlling phase) in the two-phase range. Constitutive equations were also developed on the basis of the deformation temperature range (or according to phases present) using a sine-hyperbolic type constitutive equation. The statistical analysis revealed that the constitutive equation developed for a particular phase showed good agreement with the experimental results in terms of correlation coefficient (R) and average absolute relative error (AARE).