镍基合金大锻件成形过程流变行为与晶粒尺寸预测

基于IN718合金热态成形过程中流动应力软化特征,采用动态再结晶软化本构模型来描述锻造过程中变形-传热-微观组织演变的相互作用。借助DEFORM-3D二次开发,将本构模型和微观演变模型进行耦合,模拟预测了IN718合金在多道次锻造过程中流变行为与晶粒尺寸演变,为大锻件锻造热力参数的合理制定与控制提供了依据。     

基于多场耦合分析的TC4叶片精锻成形的微观组织模拟

针对TC4钛合金叶片精锻过程,运用三维刚粘塑性有限元模拟方法,采用能反映微观组织演变对材料流动应力影响的本构关系和Yada形式的微观组织预测模型,实现了TC4叶片精锻过程的有限元变形-传热-微观组织演变耦合分析,模拟预测了叶片精锻成形的微观组织,获得了叶片精锻成形的晶粒尺寸和体积分数的分布规律,并分析了变形温度对晶粒尺寸和体积分数的影响,为合理确定叶片精锻工艺和控制叶片质量提供了一定的依据。     

Strain-rate hardening behavior of superalloy IN718

In order to produce superior feed stock for the forging of turbine disks and other components, it is necessary to better understand the effect of deformation parameters on the hot deformation behavior of IN718 during thermomechanical processing. Superalloy IN718 is a strain-rate sensitive material. In the present work, isothermal constant speed compression tests of superalloy IN718 were conducted using a computer-controlled MTS machine at temperatures of from 960 to 1040°C, with initial strain rates of from 0.001 to 1.0 s⁻¹, to engineering strains of from 0.1 to 0.7. The variation of flow stress with initial strain rate was analyzed in the paper. It was found that there was an obvious power-law relationship between flow stress and initial strain rate. From the results of these tests, a mathematical model showing the strain-rate hardening behavior of superalloy IN718 at elevated temperatures was developed. At the same time, the flow stress calculated from the model was compared with experimental results and the effect of deformation parameters on the related coefficients was analyzed.     

Effects of forging parameters on uniformity in deformation and microstructure of AZ31B straight spur gear

The effects of forging parameters on the deformation and microstructure distributions of as-forged straight spur gears were investigated by finite element (FE) simulation and statistical analysis method. Spur gear forging using the movable cavity die design was investigated by integrating the FE method with the microstructure evolution models for AZ31B magnesium alloys. The required inputs such as flow stress curves and microstructure evolution models, were obtained through the Gleeble thermal mechanical testing and quantitative metallography analysis method. Numerical simulation and experimental examination confirm that both the deformation and microstructure are non-uniformly distributed in the as-forged gears. Decreasing deformation temperature or increasing strain rate is beneficial to obtaining fine-grained microstructure but is harmful to the uniformity in deformation or microstructure. The level of the non-uniformity results from the complex shape of gear and the friction between the billet and dies, which is closely associated with the characteristics of flow stress curve.     

基于显微组织演化的本构关系的有限元变形-传热-组织演化耦合分析方法

为了使本构关系能体现热态塑性成形过程中变形-传热-组织演化之间的复杂交互作用,作者提出了一种根据显微组织演化建立材料本构关系的方法。以这种本构关系为媒介,作者进一步提出了一种热态塑性成形过程的有限元变形-传热-组织演化耦合分析方法,并建立了软件系统DHTMECA。应用DHTMECA对GH4169合金涡轮盘在液压机上锻造过程进行了变形-传热-组织演化耦合分析。计算结果表明,DHTMECA不仅可以揭示热态塑性成形过程中坯料的形状和尺寸以及坯料内热力参数的演化规律,而且能够提供热态塑性成形过程中坯料内动态再结晶过程的细节,从而在过程仿真方面为实现锻造过程最优控制和锻件组织最优化奠定基础。而这些功能是DE-FORM,AUTOFORGE,SUPERFORGE等商业有限元软件所不具备的。     

Adhesion Strength of HVOF Sprayed IN718 Coatings

The adhesion strength of high-velocity oxyfuel thermally sprayed coatings is of prime importance when thick coatings are to be sprayed in repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses, and adhesion strength were explored. The most important process parameters that influence HVOF sprayed IN718 coating adhesion strength on IN718 substrate material were identified. Residual stress distributions were determined using the modified layer removal method, and adhesion strength was measured using an in-house-developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure, and adhesion strength were established. Particle temperature, particle velocity, substrate preparation, and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for repair applications.     

Simulation of Microstructure for Hot Pack-Forging of a High Nb Containing TiAl Alloy

利用Deform-3D软件对高铌TiAl合金包套锻造过程中的微观组织演变进行模拟。为得到模拟所需参数,在1100～1250℃和0.001～0.5 s-1的条件下对合金进行了热压缩试验。在所得试验数据的基础上,利用一种间接方法建立了合金的动态再结晶模型,并利用Avrami形式的方程对再结晶分数进行描述。采用Cingara硬化模型及所建立的再结晶分数模型构建了合金的流变应力本构模型。模拟结果显示,由于锻造过程中摩擦的存在、热量的损失以及简单单向镦粗变形的锻造方式,使得坯料中的微观组织分布不均匀。通过模拟结果与实验结果的比较,证明所建立的有限元模型能够有效地预测高铌TiAl合金在包套锻造过程中的组织演变。     

Coupled quantitative simulation of microstructural evolution and plastic flow during dynamic recrystallization

A new modelling approach that couples fundamental metallurgical principles of dynamical recrystallization (DRX) with the cellular automaton (CA) method has been developed to simulate the microstructural evolution and the plastic flow behaviour during thermomechanical processing with DRX. It provides an essential link for multiscale modelling to bridge mesostructural dislocation activities with microstructural grain boundary dynamics, allowing accurate predictions of microstructure, plastic flow behaviour, and property attributes. Variations of dislocation density and growth kinetics of each dynamically recrystallizing grain (R-grain) were determined by metallurgical relationships of DRX, and the flow stress was evaluated from the average dislocation density of the matrix and all the R-grains. The growth direction and the shape of each R-grain were simulated using the CA method. The predictions of microstructural evolution and the flow behaviour at various hot working conditions agree well with the experimental results for an oxygen free high conductivity (OFHC) copper. It is identified that the oscillation of the flow stress–strain curve not only depends on thermomechanical processing parameters (strain rate and temperature) but also the initial microstructure. The mean size of R-grains is only a function of the Zener–Hollomon parameter. However, the percentage of DRX is not only related with the Zener–Hollomon parameter, but also influenced by the nucleation rate and the initial microstructure.     

基于改进BP神经网络的TA15钛合金近β锻造组织预测模型

文章以训练结果的误差均方差与误差和降低为目标,通过循环和判断语句改进了MATLAB人工神经网络(ANN)工具箱的BP算法,实现BP网络多结构、多次循环训练,建立了TA15钛合金近β锻造变形参数(变形温度、应变速率和变形量)和变形水冷(WQ)及后续热处理(再结晶退火或高低温强韧化处理)后的组织特征参数(等轴α相的含量、平均晶粒直径和轴比,条状α相的含量和厚度)之间关系的BP人工神经网络模型。结果表明,针对近β锻造组织预报输入参数多,输入-输出参数高度非线性,该模型可以有效避免传统BP模型容易陷入局部极小值点的缺点,可较准确的得到各工艺参数组合下的组织特征参数;模型预测结果可以用于近β锻造不同工艺参数组合下组织特征参数的预报,及其演化规律的分析。     

基于Murty判据的Ti-6.5Al-3.5Mo-1.5Zr-0.3Si钛合金α β相区热变形机制及工艺优化

根据Murty失稳判据,利用原始等轴组织的TC11钛合金在780～990℃和0.001～70s-1范围内的等温恒应变速率压缩实验数据,建立了该合金的加工图.依据加工图研究了TC11钛合金的变形机制和变形缺陷与变形热力参数之间的关系.结果表明,在780～990℃和0.001～0.01 s-1范围是超塑性变形区;在780～990℃和高于0.01 s-1范围,易出现β相裂纹和空洞、局部流动以及绝热剪切等流变失稳现象.根据加工图分析,结合微观组织观察结果,并考虑变形抗力的大小,确定出了较佳的变形热力参数范围为850～940℃和0.001～0.01 s-1,最佳的变形热力参数在900℃和0.001 s-1附近.     

GH4169合金惯性摩擦焊接过程组织计算与预测

以高性能航空发动机涡轮盘和压气机盘为背景，采用有限元数值模拟方法，对GH4169合金模拟件的惯性摩擦焊接过程进行了分析与计算，基于金属塑性变形的物理基础，建立了GH4169合金惯性摩擦焊接过程显微组织的演化模型；通过高温合金在热成形过程中的再结晶发生条件，再结晶体积分数、晶粒尺寸与热力参数（应变速率、应变程度、成形温度）之间的映像关系，对惯性摩擦焊接热力影响区的再结晶组织进行了模拟计算。从而为合理地制定焊接热力规范，提高GH4169合金的焊接性能和接头质量提供了参考。     

Prediction of microstructure evolution during high temperature blade forging of a Ni−Fe based superalloy,Alloy 718

The mechanical properties of the Ni−Fe-based Alloy 718 depend very much on grain size, as well as the strengthening phases, γ’ and γ. The grain structure of the superalloy components is mainly controlled during thermo-mechanical processes by the dynamic, meta-dynamic recrystallization and grain growth. In this investigation, the evolution of the grain structure in the process of two-step blade forging was experimentally and numerically dealt with. The evolution of the grain structure in Alloy 718 during blade forging was predicted using a 2-DFE simulator with implemented constitutive models on dynamic recrystallization and grain growth. The comparison of the simulated microstructure with the actual grain structure of the forged parts validated the prediction of the grain structure evolution. The effect of dynamic recrystallization on the evolution of grain structure is highlighted in this article.     

Numerical simulation on forging process of TC4 alloy mounting parts

1Introduction The TC4alloy mounting part is an important part of aeronautic engine.Currently,these mounting parts are mainly manufactured by metal cutting,which is expensive and requires a lot of manufacturing time.Furthermore,in this way the forging flow…     

TC4钛合金锻件锻造过程三维热力耦合有限元模拟

某钛合金零件是应用于航空工业的重要部件,在锻造过程中由于锻件头部变形较大,整体变形不均匀,如果模具尺寸设计不当,很容易引起锻造缺陷的产生.针对以上情况,本文建立了该钛合金锻件锻造过程的三维热力耦合有限元模型,利用刚粘塑性有限元法,对锻件的变形情况进行了数值模拟,得到了变形过程中锻件的充型情况以及温度场和应力场的场量分布,并对锻造缺陷的成因进行了分析.数值模拟与锻造试验吻合较好,为生产工艺的制定提供了有效的参考.     

重型燃机叶片锻造过程的三维热力耦合有限元模拟

利用热力耦合刚粘塑性有限元法,对某重型燃机叶片的多工步锻造过程进行了数值模拟研究。通过有限元数值模拟,分析了锻造过程中的金属流线分布,得到了温度场、应力应变场等热力参数的场量分布,从而揭示了叶片锻造的变形机理。实际锻造工艺试验与数值模拟结果吻合较好,从而验证了热力耦合有限元模型的可靠性。该研究对掌握叶片锻造变形规律具有重要意义,为叶片锻造工艺的优化设计提供了参考。     

MICROSTRUCTURAL EVOLUTION AND CONTROL IN SUPERALLOY FORGINGS

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大型锻件水空交替淬火过程的数值模拟

建立了33N iCrMoV14-5钢淬火过程温度-组织-应力耦合的数学模型,用自主有限元软件模拟了淬火过程中锻件温度场、组织场、应力场的演化过程,对不同的淬火工艺进行了比较。模拟结果表明水冷-空冷交替的淬火工艺可改善锻件表面附近的淬火应力状态,同时获得足够的心部冷速。对锻件内部应力场的计算表明水空交替淬火中,相变对应力场变化的影响大于热应力。     

SA508-3钢动态再结晶过程的相场模拟

采用多相场(Multi-phase-field,MPF)模型模拟动态再结晶晶粒的生长过程,并用Kocks-Mecking(KM)方程模拟其力学行为。用热力模拟机对SA508-3钢进行了不同温度和应变速率下的热压缩试验,从热压缩流动应力-应变曲线中提取SA508-3钢动态再结晶特征参数并用于计算动态再结晶模型参数。利用所得参数对SA508-3钢的动态再结晶过程进行了多相场模拟,预测了热塑性变形过程中的组织演变和真应力-真应变曲线,与试验结果吻合较好。试验和数值结果均表明,流动应力随应变速率的增大及变形温度的降低而增大。本文的方法可用于研究其它材料的动态再结晶行为,为优化热锻工艺提供指导。     

Microstructure Homogeneity Evaluation for TC11 Blisk Forging Using Loss Function Based on Taguchi Method

整体叶盘能够显著提高航空发动机性能。整体叶盘的质量是其在航空发动机中推广应用的重要因素。而组织均匀性是影响整体叶盘内在质量的关键因素之一。本文应用锻件内热力参数均匀性建立了基于Taguchi方法的损失函数,探索整体叶盘组织均匀性数值评价方法。应用所建立的损失函数以及TC11合金整体叶盘的锻造过程有限元数值模拟结果,对TC11合金整体叶盘组织均匀性进行了数值评价,并进行了实验验证。     

Microstructure Modeling of a Ni-Fe-Based Superalloy During the Rotary Forging Process

The microstructure evolution of Ni-Fe superalloys has a great influence on the mechanical behavior during service conditions. The rotary forging process offers an alternative to conventional bulk forming processes where the parts can be rotary forged with a fraction of the force commonly needed by conventional forging techniques. In this investigation, a numerical modeling of microstructure evolution for design and optimization of the hot forging operations has been used to manufacture a heat-resistant nickel-based superalloy. An Avrami model was implemented into finite element commercial platform DEFORM 3D to evaluate the average grain size and recrystallization during the rotary forging process. The simulations were carried out considering three initial temperatures, 980, 1000, and 1050 °C, to obtain the microstructure behavior after rotary forging. The final average grain size of one case was validated by comparing with results of previous experimental work of disk forging operation. This investigation was aimed to explore the influence of the rotary forging process on microstructure evolution in order to obtain a homogenous and refined grain size in the final component.