COLD-ROLLING AND RECRYSTALLIZATION OF (110)[110] IRON-SILICON SINGLE CRYSTALS

After70-90% cold-rolling,strong{111}〈110〉and weak {111},〈112〉 cold-rolled tex- tures and perfect{111}〈112〉 recrystallization texture were obtained in Fe-Si single crys- tals.The cold-rolled textures with different orientations possesses different ability for recov- ery because of the difference of dislocation structure and store energy alter cold-rolling.The recovery taking place at{111}〈112〉orientation region was prior to that at{111}〈110〉 orientation region.hese subgrains with{111}〈112〉 orientation became recrvstallization nuclei during their growth at expending the surrounding matrix which was sluggish in recovery process.The development of recrystallization textures may be suggested as a process of “nucleation in-situ-selective growth”.The formation of(111)textures in low carbon steel sheets has been discussed in the light of this suggestion.     

生长铜膜中孪晶形成与出现几率的分子动力学模拟

运用分子动力学和静力学方法对(111)生长铜膜中孪晶形成的原子过程与能量进行了模拟研究.所用的原子间相互作用势为Finnis-Sinclair型镶嵌原子法(EAM)势.模拟和计算分析结果表明,(111)生长铜膜表面沉积原子在不同局部可形成正常排列的fcc畴或错排的hcp畴;沉积原子处于hcp位置时体系的能量比fcc位置时要高,其增量决定了孪晶面出现几率.沉积原子错排能还受相邻{111}孪晶面的影响,其间距小于3个原子层厚时,沉积原子错排能与不形成孪晶的Al晶体表面沉积原子错排能相当,此时形成孪晶面的几率极低;随间距的增加,表面沉积原子错排能迅速降低,在间距达到约12个原子层厚以后,降到略低于完整Cu晶体{111}表面的沉积原子错排能,这表明此时出现孪晶面的几率比在完整晶体表面形成一个新的孪晶面的几率要大.     

〈111〉生长铜膜中孪晶形成与出现几率的分子动力学模拟

运用分子动力学和静力学方法对〈111〉生长铜膜中孪晶形成的原子过程与能量进行了模拟研究.所用的原子间相互作用势为Finnis-Sinclair型镶嵌原子法(EAM)势.模拟和计算分析结果表明,〈111〉生长铜膜表面沉积原子在不同局部可形成正常排列的fcc畴或错排的hcp畴;沉积原子处于hcp位置时体系的能量比fcc位置时要高,其增量决定了孪晶面出现几率沉积原子错排能还受相邻{111}孪晶面的影响,其间距小于3个原子层厚时,沉积原子错排能与不形成孪晶的Al晶体表面沉积原子错排能相当,此时形成孪晶面的几率极低;随间距的增加,表面沉积原子错排能迅速降低,在间距达到约12个原子层厚以后,降到略低于完整Cu晶体{111}表面的沉积原子错排能,这表明此时出现孪晶面的几率比在完整晶体表面形成一个新的孪晶面的几率要大.     

冷轧压下率对连续退火Ti-IF钢组织和深冲性能的影响

以工业生产的Ti-IF钢热轧板为研究材料,结合连续热镀锌线的工艺特点,采用实验室冷轧、盐浴退火方法和金相、X射线织构测试和力学性能检测等分析手段,研究了冷轧压下率对组织、织构和深冲性能的影响规律。试验结果表明,随着冷轧压下率从60%提高到90%,冷轧态α取向线上的取向密度不断增强,主要形成了{223}〈110〉和{114}〈110〉织构,γ取向线上的{111}〈011〉和{111}〈112〉织构亦有所增强;退火后铁素体晶粒尺寸从9.0级细化到10.5级,导致强度(特别是屈服强度)有所增加,η_(90°)值有所降低。试验钢退火后仍具有较强的{223}〈110〉和{114}〈110〉织构,此外,随着冷轧压下率从60%提高到80%,{111}〈110〉和{111}〈112〉织构有增强的趋势,且{111}〈110〉织构比{111}〈112〉织构强,r_(90°)值有所提高;当冷轧压下率进一步提高到90%时,{111}〈112〉织构明显增强,但{111}〈110〉织构变化较小,导致{111}〈112〉织构比{111}〈110〉织构强,使r_(90°)值反而有所降低,这与γ织构分布变化导致制耳分布曲线由典型的4制耳特征转变为6制耳特征有关。     

Simulation of Deformation Texture Evolution During Multi Axial Forging of Interstitial Free Steel

Bulk texture measurement of multi-axial forged body center cubic interstitial free steel performed in this study using x-ray and neutron diffraction indicated the presence of a strong {101}〈111〉 single texture component. Viscoplastic self-consistent simulations could successfully predict the formation of this texture component by incorporating the complicated strain path followed during this process and assuming the activity of {101}〈111〉 slip system. In addition, a first-order estimate of mechanical properties in terms of highly anisotropic yield locus and Lankford parameter was also obtained from the simulations.     

Ti-IF钢罩式退火过程中再结晶织构演变规律研究

采用X射线衍射技术(XRD)和电子背散射衍射技术(EBSD),并结合微观组织观察分析了Ti-IF钢罩式退火过程中织构演变规律和{111}再结晶织构形成机制.结果表明:随退火温度的升高,再结晶量逐渐增多,{111}再结晶织构强度亦逐渐增强,同时{100}织构强度逐渐减弱.{111}取向的品粒主要在再结晶过程中形成,依靠吞并其他取向[主要是{100}取向]的晶粒而长大;并且在{111}取向品粒长大过程中,γ纤维织构之间也发生相互转化,主要由{111}<112>织构转变为{111}<110>织构;冷轧IF钢再结晶退火后具有较强的γ纤维织构,主要是"取向形核"和"取向长大"共同作用的结果,其中Σ重位晶界在再结晶γ纤维织构形成过程中起着重要作用.     

Off-axis texture in nanostructured Ti1 − xAlxN thin films

Standard θ-2θ and pole figure X-ray diffraction techniques were used to study structural properties and preferred orientation of nanostructured TiAlN thin films prepared using cathodic arc deposition. Systematic collection of reflections from lattice planes {111}, {200}, {220}, and {311} showed that the in-plane orientation of crystallites exhibits cylindrical symmetry with random distribution of crystallites, while the out-of-plane growth presents strong texture which is inclined with respect to the surface normal. This brings the crystallographic orientation of fibre texture towards high indices lattice planes (113) and (115) contrary to traditionally grown films that develop a preferred orientation following to low indices close-packed planes (111) and (200). The origin of inclined growth is discussed taking into account the role of crystallographic defects in particular twin faults that develop in the lattice of growing crystal and change the stacking sequences of atom layers.     

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 本文通过金相和EBSD等技术,观察了不同热轧终轧温度对00Cr21Mo1铁素体不锈钢热轧态、热轧退火态、冷轧退火态织构的变化的影响情况,并分析讨论了较高终轧温度下铁素体不锈钢00Cr21Mo1塑性应变比（Rm）较低的原因。结果表明,较低的终轧温度下,00Cr21Mo1热轧态组织形变带宽度较小,受轧辊切应变而形成的{110}<001>、{110}<112>、{4 4 11}<11 11 8>织构组分强度较小,且均匀、分散,最终冷轧退火态以{111}面织构为主,塑性应变比较高。     

Variant selection during nucleation and growth of γ-massive phase in TiAl-based intermetallic alloys

This work deals with the mechanisms of nucleation and growth of γ-massive phase in TiAl-based intermetallic alloys. In particular, it focuses on the process of variant selection operating at both stages of the transformation. Small γ-massive domains produced by rapid cooling are extensively characterized by high-resolution electron backscatter diffraction. This large data set allows a statistical analysis of nucleation sites, according to different crystallographic configurations. It is established that, whatever the nucleation sites, i.e., grain boundaries or triple junctions, a coherent facet is always found presenting a Blackburn orientation relationship (BOR) between the γ nucleus and the α parent grain. Moreover, some γ nuclei can additionally present another semicoherent facet with an approximate BOR with the α host grain. A new nucleation mechanism, called “co-nucleation”, is highlighted for this type of double-faceted nucleus. Variant selection during nucleation is discussed for both types of nuclei, in terms of minimization of interface energy. In addition, it is shown that growth of γ-massive domains from their initial nucleus always involves successive {1 1 1} twinning. Variant selection also occurs either at the nucleus growth stage or during the development of successive twin generations, and is discussed in terms of interphase boundary mobility.     

Adsorption of boron and its relationship with morphologies of TiC

First-principle calculations were performed to study the adsorption of boron and its relationship with the morphologies of Ti C.It is found that although the adsorption of boron on all the low-index Ti C crystal planes is thermally favorable,it will be adsorbed more easily by C-terminated {111} and {011} planes,while less possible to be adsorbed by {001}.The study of the formation of B–B clusters indicates that the distribution of boron adatoms on C-terminated(111) and {011} planes will be more uniform,and the diffusion of the adatom further confirms the above results.According to the geometry relationship and growth rate of different crystal planes,it is deduced that the adsorption of boron on Ti C will seriously impede the growth of {111} and {011} planes,which can make Ti C grow into hexagonal platelets.     

Analysis of deformation textures of asymmetrically rolled aluminum sheets

Asymmetric rolling, in which the circumferential velocities of working rolls are different, imposes shear deformation and in turn shear deformation textures to sheets through the thickness. A component of ND//〈111〉 in the shear deformation textures can improve the plastic strain ratios of aluminum sheets. In order to understand the evolution of ND//〈111〉, the strain histories and distributions in the sheets and the texture evolution during the asymmetric rolling have been measured and calculated. The shear deformation texture can vary with the ratio of shear to normal strain increments. As the ratio increases from zero to infinity, the texture moves from the plane strain compression texture (β fiber) to the ideal shear deformation texture consisting of {001}〈110〉, {111}〈110〉, and {111}〈112〉. The ratio increases with rolling reduction per pass in asymmetric rolling. However, it is practically difficult to develop a rolling reduction per pass high enough to obtain the ideal shear deformation texture. Imposing the positive and negative shear deformations on the sheet by reversal of the shearing direction can give rise to the ideal shear deformation texture.     

Oxide nucleation on thin films of copper duringin Situ oxidation in an electron microscope

single-crystalline thin films of copper were oxidized at an isothermal temperature of 425°C and at an oxygen partial pressure of 5×10^–3 Torr in situ in a high-resolution electron microscope. The specimens were prepared by epitaxial vapor deposition onto polished {100} and {110} faces of rocksalt and mounted in a hot stage inside an ultra-high-vacuum specimen chamber of the microscope. Large amounts of sulfur, carbon, and oxygen were detected by Auger electron spectroscopy on the surface of the as-received films and were removed in situ by ion-sputter etching immediately prior to the oxidation. The nucleation and growth characteristics of Cu₂O on Cu were studied. The predominantly observed crystallographic orientations of Cu₂O on {100} and {110} copper films were epitaxial, parallel {100} and {110} orientations, respectively. In addition, a Cu₂O {111} orientation with Cu₂O 770//Cu 110 was found frequently on {100}-oriented copper films. The distinct particle shapes observed most frequently were square and hexagonal, representing {100} and {111} orientations, respectively. An induction period of about 30 min was found, which did not depend on the film thickness but did depend strongly on the oxygen partial pressure and the oxygen exposure prior to the oxidation. Neither stacking faults nor dislocations were found to be associated with the Cu₂O nucleation sites. The growth of Cu₂O nuclei was found to be linear with time. The experimental findings, including results from oxygen dissolution experiments and from repetitive oxidation-reduction-oxidation sequences, fit well into the framework of an oxidation process involving (a) the formation of a surface-charge layer, (b) oxygen saturation in the metal and formation of a supersaturated zone near the surface, and (c) nucleation, followed by surface diffusion of oxygen and bulk diffusion of copper for lateral and vertical oxide growth, respectively.This work was performed at the Ames Research Center and funded by NASA Grants NCA2-OP390-403 and NSG-2025.     

Microstructure Evolution and Hardness of an Ultra-High Strength Cu-Ni-Si Alloy During Thermo-mechanical Processing

Microstructure evolution and hardness changes of an ultra-high strength Cu-Ni-Si alloy during thermo-mechanical processing have been investigated. For hot-compressive deformation specimens, dynamic recrystallization preferentially appeared on deformation bands. As deformation temperature increased from 750 to 900 °C, elongated grains with the Cubic texture {001} 〈100〉 were substituted by recrystallized grains with Copper texture {112} 〈111〉. For the samples having undergone cold rolling followed by annealing, static recrystallization preferentially occurred in the deformation bands, and then complete recrystallization occurred. Goss, Cubic, and Brass textures remained after annealing at 600 and 700 °C for 1 h; R texture {111} 〈211〉 and recrystallization texture {001} 〈100〉 were formed in samples annealed at 800 and 900 °C for 1 h, respectively. For samples processed under multi-directional forging at cryogenic temperature, the hardness was increased as a result of work hardening and grain refinement strengthening. These were attributed to the formation of equiaxed sub-grain structures and a high dislocation density.     

微碳深冲钢板的再结晶与{111}织构的形成过程

采用试验和微观组织分析的方法,研究了冷轧微碳深冲钢板的再结晶组织和织构的特点以及AlN相析出对{111}织构形成过程的影响.研究结果表明,{111}织构从再结晶的形核阶段就已经开始形成,而且在其形成和初始长大过程中吞噬了非{111}织构组分.退火时采用慢速升温有利于AlN相充分析出和长大,促进了{111}织构的形成,从而抑制了非{111}织构组分,提高了微碳深冲钢板的成形性能.     

Effect of Annealing Treatments on the Microstructure and Texture Development in API 5L X60 Microalloyed Pipeline Steel

Effect of annealing treatments at 600, 800, 1000 and 1200 °C on the microstructure, texture, grain boundary characteristic and recrystallization fraction of Nb-microalloyed X60 steel is evaluated by using x-ray diffraction and EBSD techniques. The results indicate that bimodal as-received microstructure is changed to a homogeneous equiaxed grain structure above annealing at 1000 °C. Macro-texture investigations depict that increasing annealing temperature results in considerable variation of texture intensity, especially at 1200 °C. Maximum intensity corresponds to {001}〈310〉, Goss, copper texture components as well as near γ-fiber at 1200 °C. Recrystallization analysis shows that volume fraction of recrystallization noticeably is increased by annealing temperature at 1200 °C. Recrystallized grains are mainly oriented along γ-fiber, especially close to {111}〈112〉 texture component. Moreover, coincidence site lattice (CSL) analysis shows that the effect of annealing temperature on the volume fraction of Σ3 boundary is negligible.     

Evolution of Annealing Twins and Recrystallization Texture in Thin-Walled Copper Tube During Heat Treatment

Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation. In general, the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure. In this study, an investigation on the evolution of annealing twins as well as textures in the thin-walled (Ф6 mm×0.3 mm) copper tube underwent holding time-free heat treatment was reported. Electron backscattered diffraction analysis reveals that a large number of Σ3 boundaries (60° 〈111〉 twin relationship) are produced at the early stage of heat treatment, which is due to the lower boundary energy. With the recrystallization proceeding, the migration rate of grain boundaries decreases on account of the grain growth; meanwhile, the unique Σ9 boundaries (38.9° 〈110〉 relationship) are formed due to the interaction of the Σ3 boundaries. As a result, the number fractions of Σ3 boundaries and high-angle grain boundaries decrease rapidly. During the grain growth stage, a strong recrystallization texture was formed due to the fact that the grains of Goss orientation have a growth advantage over the others. As a result, the initial copper texture was transferred into the Goss texture in domination.     

DC06深冲开裂原因分析

通过使用光学显微镜、 X射线衍射仪和拉伸试验机等分析手段,对 DC06钢板冲压成汽车零部件过程中的开裂原因进行了分析。结果表明：冲压件 45°方向塑性应变比 r值低于标准下限,深冲有利织构 {111}〈110〉和{111}〈112〉少,导致板材变形不均匀,深冲性能差,在 45°方向应力集中区域首先产生开裂。在此基础上,提出改进措施,研究织构在热轧、冷轧及再结晶退火等加工过程中的产生及变化规律,优化生产工艺,对改进后的 DC06钢板进行测试,结果显示： DC06深冲板形成了较强的 γ纤维织构, r值升高, Δr小,板材成型性能提高。     

Abnormal growth of “giant” grains in silver thin films

Abnormal growth of “giant” grains in the millimeter range was observed in silver thin films with thicknesses of 2.0 and 2.4 μm. The effect depends on deposition temperature and deposition geometry. The microstructure and texture of as-deposited and annealed films have been characterized using X-ray, electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques. Abnormal grain growth is found whenever a special texture is formed during film deposition. Otherwise normal grain growth occurs. The texture type—and thus the grain growth mode—can be controlled by adjusting the process parameters. During abnormal grain growth, the initial 〈111〉 texture transforms completely into 〈001〉. Growth of 〈111〉-oriented grains stagnates at a size smaller than the film thickness with a non-columnar grain structure. This stagnation promotes orientation-selective growth of 〈001〉 grains.     

Effect of negative substrate bias voltage on the nucleation and growth of Cu films during the initial stage of ion beam deposition

We focused the effect of a negative substrate bias voltage on the nucleation and growth of Cu films during the initial stage of ion beam deposition. The resultant microstructure of Cu films was observed by atomic force microscopy (AFM). It was found that Cu films with or without a negative substrate bias voltage have a different dependence of nucleation and growth. It was established that the mechanism of nucleation and growth of Cu films is changed to a progressive nucleation and lateral growth by a sufficient migration of adatoms accelerated by applying a negative substrate bias voltage.     

Second-phase assisted formation of {111} twins in barium titanate

We investigated the formation mechanism of {111} twins in BaTiO₃ through systematic studies of the effects of various processing parameters on the {111} twin formation, in particular, excess TiO₂, initial particle sizes of raw materials and sintering atmosphere (either oxidizing or reducing). Our study on the effect of excess TiO₂ revealed that the second-phase Ba₆Ti₁₇O₄₀ particles provided the nucleation sites of the {111} twins. The study on the initial particle size showed that the {111} twins formed during the growth of BaTiO₃ grains around the Ba₆Ti₁₇O₄₀ particles. The twins, however, formed only when the Ba₆Ti₁₇O₄₀ interface and the BaTiO₃ grain boundaries were faceted in an oxidizing atmosphere. In a reducing atmosphere, the Ba₆Ti₁₇O₄₀ interface and the grain boundaries were defaceted (rough), and no {111} twins formed. Based on these experimental observations, we proposed a second-phase (Ba₆Ti₁₇O₄₀) assisted formation mechanism of {111} twins in BaTiO₃. The proposed mechanism explained well, all of the observed effects of the processing parameters. The mechanism may also account for the formation of annealing twins in single-phase systems with faceted grain boundaries.