HC1150/1400MS马氏体钢的高温本构模型

利用Gleeble1500热模拟试验机在温度范围600~900℃、应变速率范围10-2~10 s-1等对HC1150/1400MS马氏体钢试件进行等温拉伸试验,进而构建了马氏体钢热加工过程的数值模拟需要的高温本构模型,用以根据应变、应变速率及变形温度预测流动应力。试验得到该材料奥氏体组织在不同温度及应变速率下的真应力、真应变曲线,显示材料的流动应力随变形温度的降低和应变速率的提高而增大,随变形温度的升高和应变速率的降低而减小。选用修正的Arrhenius双曲正弦模型对其高温力学行为进行描述,采用四次多项式拟合获得Arrhenius本构方程中参数α,β,n1,n,ln A,Q与应变的对应关系,最终确定包含变形温度及应变速率的流变应力计算方程。采用拟合度表示计算应力与实测应力的相关性,拟合度结果表明该本构模型对HC1150/1400MS马氏体钢高温流动应力的预测较准确。     

铸态GH2132合金热变形行为和热加工图EI北大核心CSCD

利用Gleeble−3500热模拟机的热压缩实验,研究了铸态GH2132合金在变形温度为1173~1423 K和应变速率为0.001~10 s^(−1)条件下的热压缩变形行为和微观组织演化规律,分析该合金在不同变形条件下的热变形激活能Q值、应变速率敏感指数m值、温度敏感指数s值的变化规律,基于动态材料模型(DMM)建立热加工图,结合微观组织确定出最佳热加工参数。结果表明:随着变形温度的升高、应变速率的降低,流变应力减小,GH2132合金为应变速率和温度敏感型材料。提高变形温度、降低应变速率有利于获得均匀分布的等轴晶粒。结合热加工图和高温变形微观组织确定,铸态GH2132合金合理的热变形参数所对应的变形温度和应变速率区间分别为1295~1418 K和3.07~10 s^(−1)。     

低碳马氏体不锈钢热变形行为及本构方程

为研究低碳马氏体不锈钢的热变形行为，利用Gleeble-3800热模拟试验机对该材料进行不同温度的压缩变形试验，利用流变应力曲线构建了基于Arrhenius双曲正弦模型的本构方程，并建立试验材料的热加工图，最后对比分析试验材料在不同变形条件下的显微组织。结果表明，材料在高变形温度与低应变速率下变形时主要发生动态再结晶现象，在低变形温度与高应变速率下变形时主要发生加工硬化现象，流变应力的理论值与实测值的线性相关系数为0.995 5,验证了本构方程的准确性；结合热加工图分析和显微组织观察，得出该材料的失稳工艺窗口区域为变形温度1 020～1 120℃、应变速率0.01～1 s^-1;材料的最佳工艺窗口区域为变形温度900～1 150℃、应变速率0.003～0.01 s^-1。变形温度的提高有利于将粗大变形组织逐渐转变成细小的等轴组织，应变速率的降低同样有利于发生动态再结晶，但过低则会延长变形时间，导致再结晶晶粒逐渐长大与粗化。     

异形汽轮机叶片高温应变演化及实验研究

针对1Cr12Ni2W1Mo1V异形汽轮机叶片,通过热模拟实验获得了该材料的真应力-真应变曲线。建立了该材料的双曲正弦本构关系方程。揭示了其高温变形力学行为和流动应力变化的微观机理。对不同温度、不同变形程度和不同应变速率条件下试样的组织进行了观察。结果表明:随着变形温度的升高,材料的变形抗力减小,应力应变曲线趋于平缓;随着应变速率的提高,材料的变形抗力增大,峰值应变增加;晶粒截距和马氏体宽度都随着温度的升高而增大,随着应变速率和应变的增大而减小。     

Cu-Cr-Zr合金的高温热压缩变形行为

采用Gleeble-1500D热模拟试验机,对Cu-Cr-Zr合金在应变速率为0.001~10 s-1、变形温度为650~850℃的高温变形过程中的变形行为(流变应力和显微组织)进行研究。根据动态材料模型计算并分析该合金的热加工图,并结合变形显微组织观察确定该合金在实验条件下的高温变形机制及加工工艺。结果表明:流变应力随变形温度的升高而减小,随应变速率的提高而增大。从流变应力、应变速率和温度的相关性,得出该合金高温热压缩变形时的热变形激活能(Q)为392.5 kJ/mol,同时利用逐步回归的方法建立该合金的流变应力方程。利用热加工图确定热变形的流变失稳区,并且获得了实验参数范围内热变形过程的最佳工艺参数:温度范围为750~850℃,应变速率范围为0.001~0.1 s-1,并利用热加工图分析了该合金不同区域的高温变性特征以及组织变化。     

FGH96合金的热塑性变形行为和工艺

通过高温热压缩实验,得到了不同温度和不同应变速率条件下热等静压FGH96合金的真应力-应变曲线,在此基础上,建立了FGH96合金热塑性变形过程中的热加工图.通过对材料微观组织、应力应变响应及热加工图的对比分析,确定了优化的热塑性锻造窗口,提出了FGH96合金细晶盘坯锻造工艺.根据优化的热塑性锻造窗口,利用等温锻造工艺锻造出无开裂的细晶粒盘坯.     

加工图在Mo1材料热成形工艺控制中的应用

根据动态材料模型,建立了Mo1材料的加工图。利用加工图确定了试验材料热变形的流变失稳区。结果表明,变形量40%时,材料的流动应力变化以应变速率敏感性为主;变形量40%时,材料的流动应力变化以温度敏感性为主。此外,获得了合理的热加工窗口,应变为0.1时,即变形刚开始的合理热加工窗口为:980~1 375℃,10~0.01s-1;应变为0.5时,即变形到一定程度后的合理热加工窗口为:900~1 270℃,0.01~1.8s-1。     

粉末冶金高速钢的热变形行为

在Gleeble-1500D热模拟机上对粉末冶金高速钢进行了变形温度为1000~1150℃、应变速率为0.001~1.0 s-1;最大变形量为60%的等温热模拟压缩变形实验,并对不同变形温度和变形速率下变形试样进行了微观组织变化的观察。结果表明:流变应力和微观组织受变形温度和应变速率的影响显著,流变应力随变形温度的升高和应变速率的降低而降低,且流变应力在经历加工硬化阶段后均表现出加工软化,最后出现稳态流动特征。随着应变速率的减小,局部塑性流动减弱,回复与动态再结晶进行较充分,碳化物分布趋于均匀;随着变形温度的升高,扩散和动态再结晶更容易,发生连续的再结晶,晶粒容易长大粗化。综合考虑材料的微观组织和热加工图,最佳的热加工变形温度为1050~1100℃和应变速率为0.1~0.01 s-1。     

热加工工艺对GH4586合金微观组织的影响

在MTS热模拟实验机上采用热压缩实验的方法研究了在温度为950—1150℃、应变速率为0．001—1s^-1。的实验条件范围内，GH4586合金高温塑性变形过程中变形温度、应变速率及变形量等工艺参数对流变应力和微观组织的影响．结果表明，流变应力随着变形温度的降低和应变速率的提高而迅速增大．提高变形温度能够有效的促进动态再结晶过程，在1100℃以上变形时，在30％的工程应变量下即能够获得完全再结晶的锻态组织；当变形温度低于1050℃时，工程应变超过60％仍未观察到动态再结晶．在变形量与热处理制度一定的条件下，材料热处理后的晶粒度随变形温度的升高而增大．有效控制材料的变形温度是获得良好热加工塑性、降低变形抗力和获得均匀微观组织的关键措施．     

含稀土AZ31镁合金热压缩变形行为及加工图

在变形温度为250~400℃和应变速率为0.01~10s~(-1)的条件下,采用Gleeble-1500D热模拟试验机对含稀土AZ31镁合金进行等温恒应变速率热压缩试验,获得了其真应力-应变曲线。确定了该合金在稳态应力下的Arrhenius流动应力模型参数,并基于动态材料模型理论(DMM)建立了其热加工图。结果表明,该合金的流动应力随应变速率的升高和温度的降低而增大。结合热加工图和显微组织演化分析,确定其适宜的热成形工艺区域有两个:0.03~0.8s~(-1),250~325℃和0.01~0.9s~(-1),350~400℃。     

两种粘结固体润滑涂层的研究及应用

介绍了２种粘结固体润滑涂层的研制及其应用：（１）耐高温地固体润滑涂层,这种涂层可以在３００℃下长期使用。４００℃下短期使用,解决运动部件高温条件下的润滑和磨损问题。（２）高承载粘结固全润滑涂层。研究表明,这种粘结固体润滑涂层承载能力高,能够在普通润滑油难以承受的载荷下（如ＰＶ值高达４９００Ｎ,ｍ／ｓ的运行工况）起到良好的润滑作用。     

虚拟数控加工过程的研究

采用虚拟加工技术,设计了双刀架数控车床的虚拟数控加工系统,介绍了一种三维动画仿真技术及其特点。     

基于ISDN的视频会议系统在制造企业远程服务中的应用研究

概述了ISDN和视频会议系统。利用ISDN技术,通过Point-to-Point和B/S两种方式,给出了将视频会议系统应用于制造企业远程服务的两种实现方案。     

发动机气门组件机器人化装配的研究

以摩托车发动机缸盖气门组件的装配为研究对象,分析了用于回转式机器人柔性装配工作站的装配工艺规划,并对其中关键的气门锁片装配及装配质量检测进行了研究。     

柴油机电控喷油系统虚拟制造的研究

在集成统一的环境下,应用虚拟现实技术,人工智能技术和工程数据库技术等,运用虚拟制造的理论,建立了电控喷油系统虚拟制造的框架,提出了其主模型技术和综合可视化技术等关键技术并进行了研究,电控喷油系统虚拟制造的原型系统已部分实现。     

大齿轮齿向误差在机测量技术

从大齿轮及其齿向测量的特殊性入手,分析了大齿轮齿向在机测量的关键问题;创新提出了利用高精度水平仪调整仪器测量基准的方法和对测量数据进行系统误差补偿的思想;研究了大齿轮齿向在机测量技术和方法。     

Hot Deformation Behavior of 6061 and 7108 Al-SiCp Composites

Hot deformation behavior of Al 6061- and Al 7108-SiC particulated composites (Al-PMMCs), prepared by stir casting with SiC particulates (SiCp) size of 8 and 15 μm and volume fraction from 0 to 20% is studied by uniaxial compression test carried out at temperature range from room temperature to 500 °C. The flow stress, work hardening behavior, and Young’s modulus are determined. Dynamic recrystallization is also studied. Work hardening and Young’s modulus are directly correlated with composite constituents, whereas the flow stress is greatly influenced by the porosity and SiCp agglomeration. The role of the SiCp in increasing the flow stress decreases by increasing the deformation temperature. The dynamic recrystallization process is stimulated by refining the SiCp and increasing their fraction in soft Al matrix. On the other hand, the PMMCs with Al6061 matrix has more potential for strain hardening than that with Al 7108 matrix. The strain hardening rate is influenced by the matrix type more than the SiCp volume fraction and size.     

Constitutive Equation and Processing Map for Hot Deformation of SiC Particles Reinforced Metal Matrix Composites

Flow behavior and microstructures of Al/15% SiCp were investigated by hot compression tests using Gleeble-1500 thermomechanical simulator at temperatures ranging from 440 to 500 °C with strain rates of 0.001-1.0 s⁻¹. The high-temperature deformation behaviors of Al/15% SiCp were analyzed based on the true stress-true strain curves. The results show that the softening mechanism at low strain rate (0.001 s⁻¹) is dynamic recovery, and at high strain rates (0.01, 0.1, and 1 s⁻¹) is dynamic recrystallization (DRX). Based on these experimental data, a set of constitutive equations for Al/15% SiCp are described by the Zener-Hollomon parameter, and the coefficients of equations are found to be functions of strain. The constitutive equations reveal the dependence of flow stress on strains, strain rates, and temperatures. Furthermore, the mean error between the experimental and the calculated flow stress was computed. The result shows that the calculated results from constitutive equations are in good agreement with the experimental results. To demonstrate the potential workability of Al/15% SiCp, the processing map was established. The stable zones and the instability zones in processing map are identified and verified through micrographs. As a result, the optimum strain rates and temperatures for effective hot working of Al/15% SiCp were determined.     

Dynamic Recrystallization Kinetics and Microstructural Evolution for LZ50 Steel During Hot Deformation

The dynamic recrystallization (DRX) behavior of LZ50 steel was investigated using hot compression tests at a deformation temperature of 870-1170 °C and a strain rate of 0.05-3 s^?1. The effects of deformation temperature, strain, strain rate, and initial austenite grain size on the microstructural evolution during DRX were studied in detail. The austenite grain size of DRX was refined with increasing strain rate and decreasing temperature, whereas the initial grain size had no influence on DRX grain size. A model based on the Avrami equation was proposed to estimate the kinetics of the DRX under different deformation conditions. A DRX map, which was derived from the DRX kinetics, the recrystallized microstructure, and the flow stress analysis, can be used to identify optimal deformation conditions. The initiation of DRX was lower than Z _c (critical Zener-Hollomon parameter) and higher than ε_c (critical strain). The relationship between the DRX microstructure and the Z parameter was analyzed. Fine DRX grain sizes can be achieved with a moderate Z value, which can be used to identify suitable deformation parameters.     

Research on Flow Stress During Hot Deformation Process and Processing Map for 316LN Austenitic Stainless Steel

In this study, the hot deformation behavior of austenitic stainless steel was investigated using Gleeble-3500 thermomechanical simulator at deformation temperatures in the range of 900-1200?°C and strain rates in the range of 0.001-10?s^?1. The effects of initial austenitic grain size and deformation conditions on hot deformation behavior of 316LN were analyzed through true stress-strain curves under different deformation conditions. Both the constitutive equation and processing map for 316LN were obtained. The results show that, with the increase of the deformation temperature and the decrease of the strain rate, the peak stress decreases, and the initial austenitic grain size has a little influence on the peak stress. The relative error between the peak stress values calculated using the constitutive equation and the values measured is less than 10%. Using the processing map, the best hot-working condition for 316LN in the range of experimental deformation parameters appears when T?=?1200?°C and $\dot{\upvarepsilon } = 0.001\,{\text{s}}^{-1}.$