Investigation into Surface Defects Arising in Hot-Rolled SUP 11A Grade Spring Billets

Silicomanganese grade billets are the most commonly used steels for manufacture of automobile leaf springs. However, Cr-Mn-B grade steel known by trade name of SUP 11A grade is replacing the conventional silicomanganese grades such as 60Si7 or 65Si7 steels because it has become a competitive alternative in the market. Three heats of SUP11A grade spring steel were made through BOF-VAD-CC route and continuously cast into 125 × 125 mm billets. Some of the billets contained blowholes and piping. Rolling of selected billets into 85 × 15 mm flats revealed occasional slivers, seams, and a few shallow hairline surface cracks. A detailed metallurgical investigation was carried out to understand the genesis of these defects. A pearlite-free ferritic microstructure near the cracks combined with the presence of dispersed inclusions resulting from internal oxidation in the vicinity of cracks and the presence of scales within the shallow discontinuous short-length longitudinal cracks indicated that these defects resulted from pre-existing subsurface blowholes lying within 1 mm of billet surface. Reduction of the gas content of liquid steel in the mold, optimization of electromagnetic stirring (EMS) current, and control of superheat are some of the broad measures identified to improve the cast quality of SUP 11A spring steel billets and minimize the rejection of rolled flats.     

论绿色企业在我国的实现途径

首先讨论了绿色企业的定义并阐述了绿色企业在现代社会中的意义和作用,结合我国的实际情况提出了４条建设绿色企业的建议,最后展望了绿色企业在我国的前景。     

Discrimination Between Cracks and Recrystallization in Steel Using Nonlinear Techniques

One major problem in ultrasonic NDT for steel products and welding inspection is that standard linear methods are often unable to distinguish the nature of signals. Partially recrystallized grains, voids, small cracks or inclusions in the piece under investigation could produce indications very similar in terms of acoustic energy reflected and ultrasonic peaks envelope. Here, we analyze the nonlinear response to ultrasonic excitations of steel bars with both kind of imperfections purposefully generated. Using the Scaling Subtraction Method as a tool for the analysis, we show differences in the nonlinear signature, which can be used to distinguish nondestructively a crack/delamination from a region with imperfect grains formation, with possible applications of this technique in the production cycle.     

A Study to Relate Slab Surface Defects with FeO-Type Slivers in Hot Rolled Product

Journal of Failure Analysis and Prevention - Slivers are a common defect observed in rolled steel products such as plates and strips. This is one of the causes of rejection for applications...     

非饱和砂浆氯离子传输与pH分布相关性研究

研究了非饱和砂浆在氯盐溶液中持续浸泡、干湿循环作用下的氯离子传输和pH分布,并考虑了碳化作用对氯离子传输的影响,重点分析了氯离子传输与pH分布的相关性.研究结果表明:干燥砂浆在NaCl溶液中持续浸泡不同时间后,氯离子浓度分布与pH分布没有表现出明显的相关性;然而,在干湿循环作用下,非饱和砂浆的氯离子传输与pH分布密切相关,砂浆近表层氯离子浓度的减小与pH下降具有一致性;非饱和预碳化砂浆经干湿循环之后的氯离子浓度分布与pH分布具有相同的特征,均呈"S"型,碳化作用使砂浆的pH分布发生改变,进而影响了氯离子传输行为.     

果品蔬菜冰点同可溶性固形物含量关系的研究

果实可溶性固形物含量测定方法简单,冰点测定方法复杂,将果实可溶性固形物含量同冰点的关系建立起回归模型,可以根据可溶性固形物含量快速估算出冰点,对于果品蔬菜的冷藏和冷冻加工具有重要意义.利用T型热电偶、HP34970A数据采集仪和计算机联用,测定了24个品种果品蔬菜活组织的冰点温度以及鸭梨汁、葡萄汁和番茄汁的冰点温度,利用PR-101型折光仪测定了果实可溶性固形物的含量.结果表明,果实可溶性固形物含量和冰点温度呈高度相关,其回归方程为Y=-0.167X-0.566.24个品种果品蔬菜活组织均有典型的冰点曲线.马奶葡萄比马奶葡萄汁的冰点温度低1.2℃.     

球磨氧化铝晶粒尺寸与显微应变的关系

研究了高能球磨氧化铝的晶粒尺寸和显微应变。发现球磨后氧化铝的显微应变（ε）与晶粒尺寸（Ｄ）符合逆变关系,即晶粒尺寸越小,显微应变越大。显微应变与晶粒尺寸的倒数成线性关系,在ε～１／Ｄ图上出现双斜率。表明球磨不同阶段,显微应变增加的机制不同。     

Ti-V-Cr系阻燃钛合金厚板组织与力学性能对比研究

研究了WSTi3515S合金和TB12合金的大型铸锭成分和组织均匀性,对比分析了两种Ti-V-Cr系阻燃钛合金厚板的力学性能。结果表明:采用真空自耗电弧熔炼技术制备的Ti-V-Cr系阻燃钛合金3t级大型铸锭成分均匀;利用大型挤压机和大型快锻机制备的阻燃钛合金大尺寸厚板组织和性能均匀;两种合金的室温拉伸、硬度、冲击和540℃高温拉伸等性能相当,WSTi3515S合金在540℃条件下的热强性能较好;V和C元素有利于提高合金的热强性能,且C元素还能细化组织。     

Correlation Between Structure and Ferromagnetism in Cobalt-Doped CdSe Nanorods

The present study deals with the investigation on structural and magnetic properties of pure and Co-doped CdSe nanorods synthesized by solvothermal route. The effects of Co-doping on structural, optical, and magnetic properties of nanorods have been explored using X-ray diffraction (XRD), transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, energy dispersive spectroscopy (EDS), diffuse reflectance spectroscopy, electron spin resonance (ESR), and vibrating sample magnetometer (VSM), at room temperature. TEM images show that the synthesized nanorods having length in range of 80–150 nm and diameter of 10–20 nm. No ferromagnetic resonance signal has been observed in ESR spectra, indicating the absence of exchange interactions in pure and doped nanorods. The lattice contraction, increase in band gap, and ferromagnetic behavior have been observed with Co-doping concentration up to 5 %. However, at 10 % Co-doping concentration, reverse trend in above properties has been observed. The study reveals that there is a strong correlation between structural and magnetic properties of Co-doped CdSe nanorods.     

Correlation Between Charge Order and Second-Neighbor Hopping in Cuprate Superconductors

The correlation between the charge-order wave vector Q _CD and second-neighbor hopping t ^′ in cuprate superconductors is studied based on the t- t ^′- J model. It is shown that the magnitude of the charge-order wave vector Q _CD increases with the increase of t ^′, and then the experimentally observed differences of the magnitudes of the charge-order wave vector Q _CD among the different families of cuprate superconductors at the same doping concentration can be attributed to the different values of t ^′.     

激光熔化沉积成形缺陷及其控制方法综述

激光增材制造技术作为一种新型的快速成形技术,在快速精准成形的同时,还能够满足个性需求,这种成形方式完全颠覆了传统减材制造的成形理念,因而很快成为最能代表当今信息化时代的一种制造技术。常见的激光增材制造技术主要有以送粉为特征的激光熔化沉积技术(Laser melting deposition,LMD)和以粉末铺床为特征的选区激光熔化技术(Selective laser melting,SLM)。激光熔化沉积技术是采用同步送粉的方式通过大功率激光将同种或不同种的粉末熔化,然后逐行逐层地进行扫描堆积成形。利用这种方法所制备的零件不仅形状复杂,而且各项力学性能均优于铸件。相对于选区激光熔化技术,激光熔化沉积技术具有三大优势:(1)成形尺寸不受限制,可进行大尺寸的零件制造;(2)可以实现不同成分和比例的梯度材料成形;(3)可以进行零件修复与再制造。激光熔化沉积成形过程是一个涉及温度场、应力场等多物理场的耦合过程,由于材料急热、急冷的特点使得利用激光熔化沉积法制备的零件组织为非平衡态组织,过程复杂,不稳定性因素多,因此制件容易出现翘曲变形、熔合不良、尺寸精度不高、开裂等宏观缺陷,内部也容易产生气孔、夹杂、裂纹等微观缺陷,其中激光熔化沉积制备的零件中较大残余应力的存在使得裂纹对其性能的影响更为显著。当前,研究者们主要通过工艺实验及数值模拟研究了产生缺陷的原因,在一定程度上找出了产生气孔、熔合不良、裂纹等缺陷的主要影响因素,并针对这些因素进行逐步分析,在控制粉末特性,调节激光功率、扫描速度、送粉速度、搭接率等工艺参数,引入基板预热,热处理等缺陷控制方法方面取得了一定的进展。同时还利用外界先进检测、传感技术对缺陷进行了实时监测及闭环控制,为激光熔化沉积成形缺陷的控制提供了良好的辅助手段,大大提高了激光熔化沉积成形零件的性能。本文总结了近年来国内外有关激光熔化沉积成形缺陷及其控制方法的研究进展,按照缺陷的种类进行了分类归纳,分析了缺陷形成原因及影响因素,汇总了目前研究的缺陷控制方法,并探讨了当前存在的问题和未来发展前景。     

Correlation Between Local Atomic Symmetry and Mechanical Properties in Metallic Glasses

The local atomic symmetry was investigated and discussed for understanding mechanical, vibrational and dynamical properties in metallic glasses. Local five-fold symmetry was defined based on the ratio of pentagons to the total number of faces in a Voronoi cluster analyzed by Voronoi tessellation method. It is found that the plastic deformation prefer to be initiated in the regions with less degree of local five-fold symmetry （LFFS） and propagate gradually toward the region with more degree of LFFS. On the other hand, the local structures having less degree of LFFS contribute more to the soft low-frequency modes, and thus the so-called boson peak, while those with more degree of LFFS participate more in moderate- and high- frequency modes in metallic glasses. The relationship between local atomic symmetry and structural heterogeneity, mechanical heterogeneity, and glass transition was also discussed. It is shown that local atomic symmetry could be a general structural indicator in metallic liquids and glasses for better understanding the structure-property relationship in amorphous alloys.     

4H-SiC外延层中堆垛层错与衬底缺陷的关联性研究

本研究探讨了同质外延生长的4H-SiC晶片表面堆垛层错(SF)的形貌特征和起因。依据表面缺陷检测设备KLA-Tencor CS920的光致发光(PL)通道和形貌通道的特点, 将SF分为五类。其中I类SF在PL通道图中显示为梯形, 在形貌图中不显示; II类SF在PL通道图中显示为三角形, 且与I类SF重合, 在形貌图中显示为胡萝卜形貌。III-V类SF在PL通道图中均显示为三角形, 在形貌图中分别显示为胡萝卜、无对应图像或三角形。研究结果表明, I类SF起源于衬底的基平面位错(BPD)连线, 该连线平行于<1$bar{1}本研究探讨了同质外延生长的4H-SiC晶片表面堆垛层错(SF)的形貌特征和起因。依据表面缺陷检测设备KLA-Tencor CS920的光致发光(PL)通道和形貌通道的特点,将SF分为五类。其中I类SF在PL通道图中显示为梯形,在形貌图中不显示; II类SF在PL通道图中显示为三角形,且与I类SF重合,在形貌图中显示为胡萝卜形貌。III-V类SF在PL通道图中均显示为三角形,在形貌图中分别显示为胡萝卜、无对应图像或三角形。研究结果表明,I类SF起源于衬底的基平面位错(BPD)连线,该连线平行于1100方向,在生长过程中沿着1120方向移动,形成基平面SF。II类和大部分的III-IV类SF起源于衬底的BPD,其中一个BPD在外延过程中首先转化为刃位错(TED),并在外延过程中延0001轴传播,其余BPD或由TED分解形成的不全位错(PDs)在(0001)面内传播形成三角形基平面SF。其余的III-V类SF起源于衬底的TED或其它。II-III类SF在形貌通道中显示为胡萝卜,而IV类SF不显示,主要区别在于外延过程中是否有垂直于(0001)面的棱镜面SF与表面相交。上述研究说明减少衬底的BPD,对减少外延层中的SF尤为重要。     

基于5A90板材的电致裂纹修复模拟研究

目的 探索进一步提升5A90板材塑性成形能力的有效途径。方法 从板材内部裂纹修复的角度出发,针对脉冲电流处理技术在5A90板材上的应用进行研究。采用数值模拟的方法对脉冲电流在板材裂纹处的作用进行分析,通过计算带裂纹板材通电后其内部电流场、温度场、应力场与位移场来模拟脉冲电流对材料内部裂纹的修复机制,并采用试验件对温度场的计算结果进行初步验证。结果 脉冲电流处理对板材内部裂纹具有一定程度的修复作用,并且可以阻碍裂纹的进一步扩展。结论 脉冲电流处理可以有效减少5A90板材的内部缺陷,并提高其塑性成形能力。     

人类心理缺陷在产品设计中的研究与应用

以人类心理学中人类心理缺陷对使用产品的心理情感反应和产品设计对人类心理缺陷的反作用为研究基础,将人类,心理学、人类心理缺陷、心理障碍以及人机工程学引入到产品设计的研究过程中,针对心理缺陷和心理障碍在人群中的概况和该人群在生活中使用产品时产生的特殊,心理反应进行分析,提出了在产品设计过程中对心理缺陷是应该避免,还是针对缺陷进行辅助改进的问题,并进一步深入研究.     

掺Dy3+铁氧体纳米磁颗粒尺寸与磁学特性的相关性

在水相体系中用化学法制备出不同尺寸的掺Dy3+铁氧体纳米磁颗粒。采用透射电子显微镜(TEM)、X射线衍射仪(XRD)、超导量子干涉仪(SQUID)表征了样品的形貌、结构、室温磁学性能。TEM图片表明,样品的形貌近似球形,平均粒径在15～24nm之间;XRD图谱表明,磁颗粒的物相以Fe3O4为主,结构为面心立方尖晶石型;SQUID测试结果表明,磁颗粒的尺寸不同则磁学特性有所不同,呈现出饱和磁化强度(Ms)随粒径增大而升高的规律;粒径小则剩余磁化强度(Mr)、矫顽力(Hc)小,粒径增大则剩余磁化强度、矫顽力升高。     

A Study on Crystal Defects in Epitaxial GaN Film by High-Order Weak-Beam Electron Microscopy

Various crystal defects in epitaxial GaN film were studied by high-order bright-field and dark-field electron microscopy. The results revealed that the film is composed of small grains in nano-meter scale. Distinct shapes of the grain boundaries and a great number of threading dislocations were shown in the experimental g/3g weak-beam images. Diffraction contrast analysis verified that the majority of threading dislocations is 1/3<11 0> edge dislocation. A unique (11 0) planar defect was observed in the specimen. The defect was identified to have a similar structure to the incipient 1/3[11 0] edge dislocation.