优化工艺生产的9Cr-1Mo-V-Nb-N钢管静力强塑性评价

对经1 055 ℃正火和765 ℃回火优化工艺生产的9Cr-1Mo-V-Nb-N厚壁无缝钢管,进行室温和566 ℃的静力强塑性的检测和评估,就取样位置和取样方向对强塑性的影响进行了t统计检验评估及强塑性的标准偏差评估.结果表明,按优化工艺生产的9Cr-1Mo-V-Nb-N厚壁无缝钢管显著优于1 050 ℃正火和790 ℃回火原工艺生产的厚壁无缝钢管,强塑性指标及其标准偏差已达到进口P91厚壁无缝钢管的水平,表明我国9Cr-1Mo-V-Nb-N厚壁无缝钢管的制造技术已日趋成熟.     

薄带钢拉矫机浪形矫平过程机理建模及有限元验证

采用弹塑性力学分析方法,针对拉伸弯曲矫直机用于对具有初始位移缺陷(瓢曲浪形)薄带钢的浪形矫平过程进行机理建模,推导建立以带钢规格材质及初始浪形参数、拉矫工艺参数和拉矫机相关设备参数为自变量的拉矫变形过程浪形矫平功效的解析预测模型。通过定义拉矫过程中带钢宽向进入塑性变形的屈服区域边界位置作为中间变量,以及依次分别建立各项输入条件与屈服位置的关系、屈服位置与工艺条件的关系,建立浪形矫平预测模型的多变量微分方程组。为了验证该机理模型的正确性,分析初始浪形、材料强度、带钢尺寸等初始条件以及弯曲辊半径、拉矫张力等工艺条件对拉矫机对于带钢浪形的矫平改善能力的影响,并应用ABAQUS软件另行建立同样条件下薄带钢拉弯矫直过程的有限元模型,经计算并对比计算结果,两种方法的结果吻合良好。     

诱发钛合金塑性增强的分步超塑性成形法

介绍了分步超塑成形法,从成形方式上探索一种增强材料塑性的途径。分步超塑成形过程中,分别以恒速度与最大m值法,分两步先后作用于拉伸试样,通过控制初始变形方式的变形量以及各步间隙时间等,来促使材料内部产生晶粒细化、组织结构改善等,从而增强材料塑性。实验比较了单步拉伸成形与分步拉伸成形,以及分步成形中恒速法的预应变量对金属延伸率与组织的影响。结果表明:未经特殊细化处理的TC6钛合金分步拉伸,其恒速变形的工程应变为2.0时,可获得延伸率为2053%,而同温度下单步恒速与最大m值法拉伸的延伸率为753.9%与1347%;TC4钛合金在分步拉伸中恒速应变量为1.5时,可获得2147%的大延伸率。可见分步成形显著诱发了塑性增强。此外,预应变量决定着拉伸试样的晶粒组织大小。     

固溶处理对Fe-25Mn-1Al-0.2C钢组织性能的影响

设计了一种低层错能TWIP(Twinning Induced Plasticity)Fe-25Mn-1Al-0.2C钢,对该钢分别在900、1000和1100℃进行了固溶处理实验,研究了实验钢的微观组织和力学性能。结果表明:实验钢晶粒尺寸随着固溶温度的升高和时间的延长而增大。在1100℃时,退火孪晶贯穿整个晶粒。实验钢的抗拉强度随着固溶温度的升高而降低。当固溶温度为900℃时,随着真应变的增加,应变硬化率缓慢地降低。当固溶温度为1100℃时,均匀塑性变形分为三个阶段,并且观察到孪晶交割。     

奥氏体锰钢高应变速率孪生诱导塑性

研究了应变速率对奥氏体中高锰钢塑性的影响。结果表明：室温拉伸，中锰钢伸长率由低应变速率10^-3S^-1时的22．8％增加到高应变速率10^3S^-1时的67．4％，增加2倍；高锰钢伸长率由低应变速率10^-3S^-1时的49．5％增加到高应变速率10^3S^-1时的64．4％，增加30％。中高锰钢高应变速率增塑效应，主要与孪生变形大量启动有关，其断裂机制由低应变速率的沿晶断裂转化为高应变速率的晶内韧窝韧性断裂。     

金属材料塑性安定状态的研究

对圆环链用钢23MnNiCrMo54试样进行了一系列循环加载试验,并对试验后的记录结果进行了分析,同时对试样进行了透射电镜分析。试验结果表明,23MnNiCrMo54存在着安定状态现象,并且材料在安定状态发生后,金相组织位错密度有所增加。金属材料安定状态的存在能够为材料利用率的提高提供直接的实验和理论支持,提高目前金属构件设计中材料的许用能力。     

热处理模拟软件Thermal Prophet的开发与应用

Thermal Prophet是最近开发的一款具有自主知识产权的热处理数值模拟软件。本文介绍了其基本架构、技术特点和基本功能。以热作模具钢模块淬火为例应用本软件进行了模拟,得到的畸变趋势与实际测量结果一致。通过考虑和忽略相变塑性两种模拟结果的对比,分析了相变塑性对淬火畸变所起的作用,指出了相变塑性是模拟淬火过程不可忽略的重要因素。     

Al-6.5%Mg合金的半固态流变铸造及其性能

利用保温电磁搅拌制备半固态浆料,对Al-6.5%Mg合金的半固态流变铸造进行研究。实验中对该合金的常压铸造、液态压铸和半固态压铸所得铸件的显微组织、力学性能和拉伸断口进行分析比较。结果表明,常压铸造得到的Al-6.5%Mg合金组织为粗大的树枝晶,力学性能较低;与常压铸造相比,液态压铸件的树枝晶生长较为规则,枝晶得到细化,同时,液态压铸件的强度和塑性提高明显;半固态压铸的显微组织则为规则的球状晶,与液态压铸相比,半固态压铸件的强度略有提高,表现出更好的塑性。     

Atomic force microscopy observations of in situ deformed materials: application to single crystals and thin films on substrates

An experimental apparatus which consists of a compression machine interfaced with an atomic force microscope has been realized and allows the in situ observation of a sample surface under compressive stress. Taking advantage of the high resolution offered by this microscopy, the equipment is particularly suited both to analysing the fine slip line structure of deformed single crystals, providing interesting complementary information about plastic mechanisms taking place in the bulk, and to characterizing the mechanical behaviour of thin films on substrates with the investigation of the buckling phenomenon.     

Drawability assessment of BCC steel sheet by using elastic/crystalline viscoplastic finite element analyses

Elastic/crystalline viscoplastic finite element (FE) analyses were carried out to asses the drawability of three kinds of BCC steel sheets, such as mild steel, dual-phase steel and high-strength steel, in the cylindrical cup deep drawing processes. In this study, the crystal orientations were obtained by X-ray diffraction and orientation distribution function (ODF) analyses. The measured ODF results have revealed clearly different textures of sheets, featured by orientation fibers, skeleton lines and selected orientations in Euler angle coordinate space, which can be related to the plastic anisotropy. An orientation probability assignment method, which can be categorized as an inhomogenized material modeling, was used in this FE modeling. The orientations were determined from the measured ODF and assigned to FE integration points one by one. Numbers of integration points, which represent crystallites and can rotate individually, are employed to represent textures of the sheet metals for taking account of the initial and evolutional plastic anisotropy without introducing Taylor or Sachs homogenization assumption. The FE analyses showed how the fiber textures affect the strain localization and earing in the deep drawing operation. It was confirmed by comparison with experimental results that this FE code could predict the extreme strain localization and earing with good accuracy and assess the sheet drawability.