Texture evolution of 440 MPa grade Nb-bearing high strength IF steel during rolling and annealing process

The texture evolution from rolling process to annealing process of 440 MPa grade Nb-bearing high strength IF steel (IF-HSS) was studied. Moreover, the texture of different section in thickness direction of steel sheet after annealing was investigated. Macro-texture measurements using XRD shows that hot rolling texture in Nb-bearing IF-HSS includes a weak γ-fiber and α-fiber, of which main texture components are {001}<110>,{111}<110> and {111}<112>. It is worthy of note that the γ-fiber skeleton line formed after hot rolling. During cold rolling, the absolute maximum shifts to {111}<112> along the γ-fiber and the maximum along the α-fiber shifts to {112} <110>. During recrystallization annealing process, the weaker α-fiber and stronger γ-fiber cold rolling texture transformed to a very strong γ-fiber annealing texture. After annealing the main components from surface to mid-section along thickness display the same character for both α-fiber and γ-fiber, while textures intensity at 1/4 section is higher than that of surface and mid-section.     

Superplastic deformation behavior and mechanism of 1420 Al-Li alloy sheets with elongated grains

True stress-true strain curve, microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains. From the true stress-true curve, the stress increases with the increase of strain to 0.15, then dramatically decreases with the increase of strain to 0.80, and finally keeps almost a horizontal line. Meanwhile, initial elongated grains are gradually changed into equiaxed grains and the initial strong Brass {0 1 1} 〈2 1 1〉 and S {1 2 3} 〈6 3 4〉 orientations are turned into nearly random orientation with increasing strain. All these results suggest that dislocation activity is the dominant mechanism during the first stage, then dynamic recrystallization occurs, and grain rotation is expected as an accommodation for grain boundary sliding (GBS). At larger strains, grain boundary migration (GBM) becomes necessary to accommodate GBS.     

Microstructure evolution of single crystal copper wires in cold drawing

The deformation microstructure evolution of single crystal copper wires produced by OCC method has been studied with the help of TEM, EBSD and OM. The results show that there are a small number of dendrites and twins in the undeformed single crystal copper wires. However, it is difficult to observe these dendrites in deformed single crystal copper wires. The structure evolution of deformed single crystal copper wires during drawing process can be divided into three stages. When the true strain is lower than 0.94, macroscopic subdivision of grains is not evident, and the microscopic evolution of deformed structure is that the cells are formed and elongated in drawn direction. When the true strain is between 0.94 and 1.96, macroscopic subdivision of grains takes place, and the number of microbands located on {111} and cell blocks is much more than that with the true strain lower than 0.94. When the true strain is larger than 1.96, the macroscopic subdivision of grains becomes more evident than that with the true strain between 0.94 and 1.96, and S-bands structure and lamellar boundaries will be formed. From EBSD analysis, it is found that part of 〈100〉 texture resulting from solidifying is transformed into 〈111〉 and 〈112〉 due to shear deformation, but 〈100〉 texture component is still kept in majority. When the true strain is 0.94, the misorientation angle of dislocation boundaries resulting from deformation is lower than 14°. However, when the true strain arrives at 1.96, the misorientation angle of some boundaries will be greater than 50°, and the peak of misorientation angle distribution produced by texture evolution is located in the range between 25° and 30°. Supported by the National Natural Science Foundation of China (Grant Nos. 50471098 and 59971033), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2003E101), and the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institution of MOE, China     

Modeling texture development during cold rolling of IF steel by crystal plasticity finite element method

With the consideration of slip deformation mechanism and various slip systems of body centered cubic (BCC) metals,Taylor-type and finite element polycrystai models were embedded into the commercial finite element code ABAQUS to realize crystal plasticity finte element modeling,based on the rate dependent crystal constitutive equations.Initial orientations measured by electron backscatter diffraction (EBSD) were directly input into the crystal plasticity finite element model to simulate the development of rolling texture of interstitial-flee steel (IF steel) at various reductions.The modeled results show a good agreement with the experimental results.With increasing reduction,the predicted and experimental rolling textures tend to sharper,and the results simulated by the Taylor-type model are stronger than those simulated by finite element model.Conclusions are obtained that rolling textures calculated with 48 {110}<111>+{ 112}<111>+{123}<111> slip systems are more approximate to EBSD results.     

Texture of deformed Cu-Cr-Zr alloys

The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were explored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}<331> and {110}<112> were predominated, whereas, those of {113}<332> and {112}<111> were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (>0.5wt%). However, in the samples with a lower Zr content (<0.1wt%), the texture contents of {113}<332>, {112}<111>, and {111}<110> were in the majority.     

Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (λN) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These λN laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of λN lath. The first is a genuinely {111} twin, and λN and α keep the accurate K-S relationship, and each λN and α form a sharp and smooth λN/α interface of {335}λN//{341}a, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of λN due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the λN and the (-matrix deviate from the accurate K-S OR, and the OR between two λN twin components deviate from the genuine {111} twin relationship. In addition, the λN/α interface of the second type of λN is not as sharp or smooth as that of the first one.     

多晶铜轴对称变形织构的纵向塑性各向异性

应用Taylor类多晶体塑性模型对轴对称变形下多晶铜的变形织构进行了数值模拟,分析了变形过程中多晶铜屈服应力的各向异性演化情况;计算分2步:先对随机分布多晶集合体进行轴对称拉伸,然后分别沿已变形的多晶集合体的各方向再进行拉伸变形,得到了屈服应力的取向分布及纵向塑性各向异性的直观图像,为变形织构塑性各向异性力学行为的宏观模型描述提供了一个数值实验。     

体心立方晶体{110}<1■1>滑移系棱锥在确定独立滑移系时的应用

本文运用塑性理论和{110}〈1■1〉滑移系棱锥分析了体心立方晶体中{110}〈(?)〉滑移系的独立性,描述了各类滑移系组的组合规律及其晶体学特征。     

谈体心立方晶体{110}<1■1>滑移系全位错的滑移方式

本文从体心立方点阵中抽取一个滑移系棱锥来描述12个(110)(1(?)1)滑移系。根据滑移系棱锥可以清晰识别正交和斜交滑移面;本文讨论了在斜交{110)滑移面上螺位错和刃位错的滑移行为。     

Microstructure and texture evolution during warm compression of the magnesium alloy AZ31

The evolution of the microstructure and texture with strain during compression at 150℃ of the magnesium alloy AZ31 has been investigated using the electron backscattered diffraction (EBSD) technique. The initial samples were chosen to have a strong basal plane texture with the crystal c-axes perpendicular to the compression direction. The EBSD data provide evidence concerning the relative activity of both {10-12} extension twinning and slip, and suggest that non-basal slip is important in samples deformed to a strain of more than 0.2. The relative contributions of the twinning and the slip during deformation have been discussed based on the results above.     

CSP冷轧薄板退火工艺的研究

采用EBSD分析方法,对CSP试验钢冷轧板退火过程中组织转变和再结晶织构的演变进行分析,结果表明,试验用钢的再结晶过程属于定向形核理论,试验钢的再结晶形核阶段在{111}112冷轧基体上形成了{111}110和{110}100再结晶形核,在{111}110变形晶粒晶界形成{111}112新晶粒核心,{111}112和{111}110织构相互生成.在晶粒长大阶段消耗的大量的{100}110织构,且生成了{112}110织构.     

Dynamic recrystallization-induced temperature insensitivity of yield stress in single-crystal Al1.2CrFeCoNi micropillars

High-entropy alloys, a new class of metallic materials, exhibit excellent mechanical properties at high temperatures. In spite of the worldwide interest, the underlying mechanisms for temperature dependence of mechanical properties of these alloys remain poorly understood. Here, we systemically investigate the mechanical behaviors and properties of Al_(1.2)CrFeCoNi(comprising a body-centered cubic phase) and Al_(0.3)CrFeCoNi(comprising a face-centered cubic phase) single-crystal micropillars with three orientations([100], [110], and [111]) at temperatures varying from 300 to 675 K by using in situ compression of micropillars inside a scanning electron microscope. The results show that the yield stresses of Al_(1.2)CrFeCoNi micropillars are insensitive to temperature changes, and their flow stresses and work hardening rates increase slightly with increasing temperature from 300 to550 K, which differs from the typical temperature dependence of yield/flow stresses in metals and alloys. In contrast,Al_(0.3)CrFeCoNi micropillars exhibit typical thermal softening. Furthermore, it is found that the Al_(1.2)CrFeCoNi micropillars exhibit a transition from homogenous deformation to localized deformation at a critical temperature, while the Al_(0.3)CrFeCoNi micropillars always maintain a well-distributed and fine slip deformation. Detailed transmission electron microscopy analyses reveal that dynamic recrystallization(involving dislocation tangles, and formation of dislocation cell structures and sub-grains)plays a key role in the observed temperature insensitivity of the yield stress and increasing flow stress(and work hardening rate)with increasing temperature in the Al_(1.2)CrFeCoNi micropillars, and that thermally activated dislocation slip leads to thermal softening of the Al_(0.3)CrFeCoNi micropillars. The differences in deformation modes and temperature dependence of the mechanical properties between Al_(1.2)CrFeCoNi and Al_(0.3)CrFeCoNi essentially originate from the differences in dislocation activities and slip systems since the two alloys adopt different phases. Our findings provide key insights in the temperature dependence of mechanical properties and deformation behaviors of high-entropy alloys with body-centered cubic and face-centered cubic phases.     

Structure and growth phenomena of C60 and C70 single crystals

C₆₀ and C₇₀ single crystals free from solvent contamination grew from their vapour. Large C₆₀ crystals up to a size of about 5 mm×3 mm×3 mm and C₇₀ crystals about 1 mm×1 mm×1 mm were obtained. C₆₀ crystals with fcc structure showed two types of morphological faces, namely {111} and {100}, frequently with twinning on {111} face. C₇₀ crystals obtained have a hcp structure witha=10.1 ? andc=16.7 ?. DSC and X-ray diffraction analysis indicated that C₇₀ crystal underwent phase transition below 100 C. Morphological observation suggests that the growth of C₆₀ and C₇₀ single crystals is based on layer-spreading mechanism. Synopsis of the first author Li Jing, professor, born in 1954, received Ph D degree in 1988, professional interests are physicel chemistry in metallurgy and materials, fullerene chemistry and ceramics.     

IF钢生产过程中的织构演变

对IF钢生产过程中热轧、冷轧及退火试样的织构演变进行研究。分别借助EBSD和XRD测定和计算了热轧、退火及冷轧试样的取向分布函数及相关织构组分的体积分数。结果发现,热轧板在变形过程中发生了动态再结晶,晶粒为细小的等轴晶,为后续组织发展提供了基础;热轧后试样中的织构很弱,不会影响冷轧织构组分及含量。冷轧过程是织构形成的主要过程,试样中含有4种主要的织构组分：{001}〈110〉、{111}〈110〉、{111}〈112〉和{112}〈110〉。退火过程中发生再结晶,4种冷轧织构组分在退火过程中均分别转变为{111}面织构。     

Effects and mechanism of titanium modification on structures of cast steel ZG270-500

The influences of titanium modification on the solidification behavior, shrinkage characteristic and primary austenite refinement of cast steel ZG270-500 smelted in intermediate frequency induction furnace were studied. 0.15wt% titanium modification increased the fluidity of the steel liquid, enhanced the feeding capacity of cast steel, changed the dispersed shrinkage porosity to concentrated shrinkage cavity, turned the coarse dendrites into fine equiaxed grain structures and greatly reduced the primary austenite grain size. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that titanium combined with carbon to be solid phase particles TiC, with high melting point, to promote the primary austenite nucleation authentically by non-spontaneous nucleating. The crystal lattice match growing model between γ-Fe and TiC was established. The mechanism of TiC heterogeneous nucleating existed in that the primary austenite grew up by {111}γ-Fe parallel to the closest packed plane {111}TiC in the crystal orientation <110>γ-Fe//<211>TiC. The crystal planes mismatch and the lowest orientation mismatch δ<110>γ-Fe <110>TiC were 8.18%. and 2.25% respectively, almost achieving complete coherent lattice match growing of austenite on TiC.     

Cold Rolling Texture in Ordered CuZn Alloy

The texture of 80% cold rolling CuZn ordered alloy was investigated. The development of rolling texturein 50%Cu-50%Zn(at.) alloy has been characterized by a inhomogenous {111} fiber texture with strong {111} <112>component, which is significantly different from the conventional Cu-Zn alloys. The main characters of cold rollingtextures in ordered CuZn alloy are obviously similar to that in IF steel with bcc structure or ordered Fe3A1-basedalloys with imperfect B2 structure. From the rolling texture obtained by experiments and simulations,it can be estimated that main deformation mechanism are characterized by the activation of slip systems with <111> Burgersvector in CuZn ordered alloy.     

COMPUTER SIMULATION OF DISLOCATION CORES IN B2 NIAL INTERMETALLICS *

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道次压下率及几何因素对Al-Mg-Si合金冷轧织构的影响

采用取向分布函数（ODF）分析并研究了Al-Mg-Si合金在冷轧过程中织构的演变及轧制工艺对冷轧织构的影响.结果表明：Al-Mg-Si合金冷轧后,主要轧制织构组分均为Copper织构组分、 S织构组分和 Brass织构组分,另有较弱的Goss织构组分;冷轧过程中,在道次压下率和几何因素均较大的条件下会产生较强的旋转立方织构,而且继续轧制时,随着轧板的减薄,旋转立方织构会迅速减弱而且Copper、Brass、S等正常轧制织构组分迅速增强.此外,在总轧制形变量相同的条件下,随着道次压下量的提高,轧制织构减弱.     

高锰TWIP钢拉伸时织构演变和孪生弱化织构的作用

研究室温下锰的质量分数分别为26%和30%的两种晶粒较粗大的TWIP钢拉断过程中织构的演变规律及孪生弱化〈111〉织构的作用。结果表明,TWIP钢拉伸时形成较强的〈111〉织构,也形成由〈111〉取向晶粒的不同孪晶产生的接近〈100〉的弱织构,从而孪生弱化了〈111〉拉伸织构。粗的奥氏体晶粒促进孪生,从而加速〈111〉织构的弱化。拉伸过程中〈111〉取向的晶粒有利于形变孪生,〈100〉取向的晶粒不利于孪生。锰含量较低的26Mn钢出现少量的形变诱发ε-M,由于ε-M主要从〈111〉取向的形变孪晶内形成,因此也出现择优取向,形成倾转的基面织构,弱化了〈111〉织构。     

退火温度对Ti-IF钢性能及织构的影响

对冷轧压下率为80%、厚1 mm的Ti-IF钢经不同温度退火处理后进行拉伸试验,测量其塑性应变比r值。观察退火试样的显微组织,并利用电子背散射衍射技术（EBSD）对其性能和再结晶织构进行分析。结果表明,冷轧试验钢分别在780、810、840℃退火3 min后,均发生了再结晶;随着退火温度的升高,大多数晶粒尺寸由5-6μm增大到9-10μm;试验钢的r值随退火温度升高而增大;退火钢再结晶织构表现为强烈的{111}织构,主要由{111}〈110〉和{111}〈112〉两类取向晶粒组成。