Texture Evolution of Columnar Grains in Electrical Steel During Hot Rolling

Columnar grains in cast slabs of electrical steel show strong anisotropy in grain orientation and morphology and thus influence the subsequent microstructure and texture after hot rolling significantly. The texture evolution of hot rolled sheets containing initial columnar grains with their <100> directions approximately parallel to the rolling direction (RD), transverse direction (TD) and normal direction (ND) of the hot rolled sheets was investigated by using EBSD technique. The results indicated that, whatever the initial texture of the columnar grains was, typical Goss, brass-type and copper-type shear texture component could develop in shear-deformed surface region. The copper-type texture formed under the maximum shearing force with the fine, sheared or dynamically recrystallized grains, and Goss grains were mainly elongated and deformed grains, while brass grains behaved between them. Additionally, the rotating relationship of the three types of shear textures was different due to the restriction of grain boundaries. In homogenously deformed center region, the RD sample contained more {112} <110> grains, and TD sample was covered by {100} textures such as {100}<011> and {100}<021> with coarse grains, while the ND sample developed many {100}<011> grains which were attributed to more {100} grains in the initial sample. Remarkable texture transition occurred on both sides of grain boundaries when {110} grains were adjacent to α-fiber texture grains. It was found that significant texture gradient and preferred distribution of rotating axis existed in the soft orientation grains on the α-fiber when the grains neighbored hard grains on γ-fiber.     

Ni/Ni_3Al两相合金箔材的退火行为研究

研究了冷轧变形95%的Ni/Ni3Al两相合金箔材在经过100h退火后的再结晶过程以及织构和晶粒的微取向的变化。对其织构的测量未表现出如冷轧单相Ni3Al合金退火后所具有的织构记忆效应。EBSD(electron back-scattered diffraction)的测量结果显示退火后根据晶粒的取向可分为两个区域,一个区域的晶粒保持了与冷轧后试样的晶粒相同的取向,即其取向为(110),并且这一区域沿轧制方向呈带状分布,而另一个区域的晶粒的取向则为随机的。两个区域中(110)取向晶粒所占的百分比依次为57%和16%,并且在长时间退火后这种带状结构依然存在。冷轧变形95%的Ni/Ni3Al两相合金箔材在600～800℃之间退火时存在两种再结晶过程。一部分区域退火后生成大量的晶粒取向随机分布的再结晶晶粒,而在另一部分区域则其再结晶晶粒保持与冷轧织构相同的晶粒取向,并随着退火温度的升高而长大。     

Textures of low carbon and titanium bearing extra low carbon steel sheets hot rolled below their AR3 temperatures

The textures of warm rolled low carbon and Ti-bearing extra low carbon steel sheets have been investigated using ODF's ECC-ECP (electron channeling contrast-electron channeling pattern) and selected area electron diffraction and the following results were obtained: (1) The main orientation of the low carbon steel sheet was near {113}〈110〉 while that of Ti-bearing extra low carbon steel was near 〈111〉//ND. (2) The recrystallization of the low carbon steel occurred mainly from deformed {100} grains while the main nucleation sites in the Ti-bearing extra low carbon steel were the grain boundaries of the deformed {111} grains. (3) The main orientations of grains recrystallized from deformed {100} grains are {100}〈110〉−{112}〈110〉 for both steels. (4) The orientation of the grains recrystallized from the deformed {111} grains of the Ti-bearing extra low carbon steel is mostly near 〈111〉//ND and that of the low carbon steel is mainly near {114}〈110〉. This difference is discussed in terms of the influence of carbon in solution on the crystal rotation at nucleation sites. (5) It is concluded that the different recrystallization textures formed in the two steels is explained by the difference in the preferred nucleation sites and in the local crystal rotations in the vicinity of grain boundaries.     

Surface segregation and directionality of {110} grains in electrical steels containing Sn and Sb

A repulsive segregation behavior between sulfur and tin or antimony was observed. Tin and antimony as well as sulfur governed the selective grain growth. In the tin- and the antimony-added strips, the deviation angle distributions between the 〈001〉 crystal direction of {110} grains and the rolling direction after final annealing were broad, compared to that in the strip without the solutes. This is due to a {001} cold-rolling texture with a deviation angle between the 〈001$x232A; crystal and the rolling directions that results in the initial annealing texture detrimental to the formation of sharp {110} 〈001〉 texture. This research was supported by a grant from the Center for Advanced Materials Processing (CAMP) of the 21st Century Frontier R&D Program funded by the Ministry of Science and Technology, Republic of Korea.     

取向硅钢薄带形变再结晶组织及织构演变

利用背散射电子衍射微织构分析技术及X射线衍射织构分析技术,结合对取向硅钢薄带再结晶各阶段退火板磁性能的分析,系统研究了其形变再结晶过程中的组织及织构演变.结果表明,薄带内原始高斯晶粒取向发生绕TD轴向{111}〈112〉的转变,同时晶粒取向还表现出绕RD轴的附加转动,这种附加转动及其导致的表层微弱立方形变组织可为再结晶立方织构的形成提供核心.退火各阶段样品磁性能的变化对应了{110}-{100}〈001〉有益织构及其他织构的强弱转变以及再结晶晶粒不均匀程度的变化,综合织构类型及晶粒尺寸的变化推断发生了二次及三次再结晶过程.升温过程再结晶织构演变主要体现了织构诱发机制,也即与基体存在绕〈001〉轴取向关系的晶粒长大优势结合高斯织构的抑制效应发挥作用;而在高温长时间保温后三次再结晶过程,{110}低表面能诱发异常长大发挥主要作用使得最终得到锋锐的高斯织构.      

Orientation and temperature dependence of slip in iron single crystals

The orientation and temperature dependence of slip in ZrH₂-purified iron crystals have been investigated at strains up to about 15 pct. Both {110} and {112} slip planes were observed at all temperatures investigated (295°, 250°, 195°, and 143°K) when the orientation of a crystal was such that its maximum resolved shear stress plane (MRSSP) corresponded to {110} or {112}. At 195° and 143°K {110} and {112} slip planes were also observed for orientations where the MRSSP deviated from {110} or {112} slip planes were also observed for orientations where the MRSSP deviated from {110} or {112}. At 295° and 250°K, the slip planes of crystals whose MRSSP was not {110} or {112} deviated from the MRSSP toward {110}. The variation in the intensity and waviness of the slip traces with orientation suggested that cross slip was easiest for orientations that slipped on a {112} plane in the twinning sense (near [001]), and hardest for orientations that slipped on a {112} plane in the antitwinning sense (near [011]). This appears to be in accord with observations of easier dislocation multiplication for orientations near [001] than for orientations near [011]. At 143°K the critical resolved shear stress law was not obeyed; the resolved shear stress was about 14 pct lower for slip on a {112} plane when the sense of the applied stress was favorable for twinning than when it was unfavorable. The slip line observations and the asymmetry of slip on a {112} plane appear to be qualitatively explainable in terms of dissociated dislocation models that are based on differences in the ease with which slip and cross slip can occur on {110} and {112}.     

Fracture of single crystals of the nickel-base superalloy PWA 1480E in helium at 22 °C

The fracture behavior of single crystals of the PWA 1480E nickel-base superalloy was studied using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Notched single crystals with seven different crystal growth orientations near [100], [110], [111], [013], [112], [123], and [223] were tensile tested at 22 °C in a helium atmosphere at 34 MPa. Gamma prime particles were orderly and closely aligned with the cube edges along the [100], [010], and [001] directions of theγ matrix. The cuboid morphology of theγ’ precipitate was not influenced by the crystal growth orientation. The specimen with the [110] orientation was the strongest, while the crystal with the [100] orientation was the weakest. A stereoscopic technique, combined with the use of planary’ morphologies, was applied to identify the cleavage plane orientation. All specimens failed predominately by {lll}-type cleavage which originated from combined slip on various {111} planes. In most cases, deformation was found to occur inhomogeneously in intense slip bands lying on {111} planes and aligned parallel to the different slip directions. Both SEM and TEM studies indicated that {lll}-type slip was the controlling factor during cleavage fracture of single crystals of the PWA 1480E nickel-base superalloy. Formerly Graduate Student, Auburn University     

取向硅钢板坯加热温度对热轧及冷轧板织构的影响

 采用取向分布函数及取向线分析方法对取向硅钢高温和低温板坯加热工艺的热轧及冷轧钢板织构进行了研究。结果表明：低温与高温板坯加热工艺的热轧板及冷轧板织构组分有明显不同。低温板坯加热热轧板中{100}<001>及{110}<110>织构较强,但经冷轧后{001}<110>织构最强。     

Orientation degree characterization of diamond etched with Ce-7%Fe alloy

An increasing {110} orientation degree behavior was observed during etching of chemical vapor deposition (CVD) diamond films by partially melting Ce-7%Fe alloys. In order to accurately investigate this phenomenon, the X-ray diffraction method was used to identify the changes in the surface crystal orientation of the diamond films etched by Ce-7%Fe alloys, and evolution of orientation along the growth direction of the un-etched diamond film was analyzed by electron backscattering diffraction (EBSD), and then the morphology of etched diamond surface was observed by scanning electron microscopy (SEM). The results showed that the {110 } orientation degree of diamond surface increased due to the anisotropy in diamond etching with Ce-7%Fe, which was verified by the etching "pit" in SEM micrographs.     

退火工艺对3.15 % Si冷轧无取向硅钢组织和织构的影响

试验研究了退火温度（850~950℃）和时间（5~18 min）对2.3 mm热轧硅钢板（/%:0.036C,3.15Si,0.21Mn,0.005P,0.007S,0.032Al）6道次轧制的0.35 mm冷轧板组织和织构的影响。结果表明,退火温度越高,晶粒平均尺寸越大,900℃5 min退火时平均晶粒尺寸41.39μm,试样织构主要集中在γ取向线上的{111}＜112＞;织构组分和{111}＜110＞;织构组分;900℃18 min退火时平均晶粒尺寸为48.08μm,试样的{111}面织构和{112}面织构密度都明显减弱,{001}面织构增强,磁性能较优。     

Dependence of Crystallographic Orientation on Pitting Corrosion Behavior of Ni-Fe-Cr Alloy 028

The influence of crystallographic orientation on the pitting corrosion behavior of Ni-Fe-Cr alloy 028 was studied using a combination of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), potentiodynamic polarization technique, and atomic force microscopy (AFM). The results show that there is anisotropy of pitting corrosion that strongly depends on crystallographic orientation of the surface plane. The distribution of pit density in a standard stereographic triangle indicates that the crystallographic planes close to {100} are more prone to pitting corrosion compared to planes {110} and {111}. The surface energy calculation of (001) and (111) shows that the plane with a high atomic packing density has a low surface energy with concomitant strong resistance to pitting corrosion. A correlation function between crystallographic orientation and pitting corrosion susceptibility suggests a method that not only predicts the pitting resistance of known textured materials, but also could help to improve corrosion resistance by controlling material texture.     

Atmosphere change of vacuum to hydrogen and sharpness of {110}〈001〉 texture in thin-gaged 3 Pct Si-Fe alloy strips

Heating in vacuum finally resulted in a main {100}〈uvw〉 texture and a trace of {111}〈uvw〉 texture. However, the texture was changed to the {110}〈001〉 texture when the strip was heated in hydrogen or when the vaccuum was changed to hydrogen at a temperature T_c. As T_c increased, the sharpness of the {110}〈001〉 texture increased, resulting in the high magnetic induction. This can be understood in the light of surface segregation kinetics of sulfur.     

Plane strain compression of silicon-iron single crystals

Six different orientations of Fe-3 wt% Si single crystals have been deformed in plane strain compression (using a channel die) up to true strains of 0.5. The finite strain behaviours, i.e. the shape changes, lattice rotations and stress-strain curves, are compared with the predictions of the generalized Taylor analysis of partially constrained crystal deformation. The influence of the relative critical resolved shear stresses on the {110} and {112} 〈111〉 glide systems has been systematically examined. It is shown that for most crystals under multiple slip conditions the shape changes and lattice rotations are consistent with the hypothesis of glide on {112} being somewhat easier than on {110}. Comparison with previous work on b.c.c. crystals undergoing large strains leads to the suggestion that: (i) under conditions of single or colinear slip, glide on {110} is easier than on {112}; (ii) under conditions of intersecting 〈111〉 slip directions, glide on {112} is easier than on {110}. For silicon-iron, the critical resolved shear stresses on the {112} 〈111〉 systems, relative to those on the {110}〈111〉 systems are found to be 0.93 and 0.96 for the twinning and anti-twinning senses, respectively.     

A crystallographic study of fatigue damage in titanium

Large grain specimens with average grain size of 0.0127 m made from commercial purity titanium were subjected to a torsional cyclic strain at two different amplitudes: ±0.008 and =0.003. Fatigue damage was studied by scanning electron microscopy and crystal orientations were determined by X-ray diffraction and surface trace analysis. It was found that cyclic strain amplitude influenced the deformation mode and the nature of the macroscopic crack propagation. At high strain amplitudes the normal slip processes were observed and microcracking was observed on the (0001), and {1100} slip planes. The macroscopic crack propagation was dominated by the Stage I shear mode; however, some Stage II tensile mode propagation was observed after extensive Stage I propagation. At low strain amplitude twin plane cracking was observed on the {1011}, {1010}, and {1123} planes in addition to normal slip plane cracking, and the macroscopic crack propagation was dominated by the Stage II tensile mode. However, microscopic examination showed the macroscopic tensile mode cracks to be composed of microscopic shear mode cracks along slip planes and twin planes. At both low and high strain amplitudes cracking was observed on the {1120} plane which is neither a slip or twin plane in titanium. It is proposed that this cracking mode was a result of a dislocation reaction forming sessile dislocations on the {1120} plane.     

纯铁纯度对其再结晶织构及晶粒Schmid因子的影响

 为了研究纯铁纯度对其再结晶织构及Schmid因子的影响,以商业的2N8、3N5纯铁和实验室制备的4N级公斤级高纯铁为原料,通过退火再结晶和EBSD研究了2N、3N、4N纯度纯铁再结晶织构特征和晶粒的Schmid因子。结果表明,2N8、3N5和4N3纯铁的晶粒组织均为等轴铁素体,残余应力少、位错密度低,样品再结晶完全。其中,2N8和3N5纯铁的织构呈现出相同的分散分布特征,而4N3高纯铁织构特征集中,随机织构较少。ODF图和取向线分布密度进一步表明,2N8和3N5纯铁具有相似的α织构{hkl}〈110〉和γ织构{111}〈uvw〉特征及变化趋势,即两者都在α取向线的{111}〈110〉取向具有较高的分布密度和γ取向线密度随φ₁的增大而有降低;而4N3高纯铁具有〈113〉|X和γ织构特征,且包含利于材料力学性能各向异性的{332}〈113〉织构,另外,其γ取向线密度随φ₁的增大逐渐升高,直至{111}〈112〉取向密度高于2N8和3N5纯铁。晶粒Schmid因子及其频率分布直方图结果表明,2N、3N、4N纯铁均存在低Schmid因子晶粒被高Schmid因子晶粒包围的现象,且在{110}〈111〉、{112}〈111〉和{123}〈111〉这3个滑移系下晶粒Schmid因子总和平均值为0.467(4N3)＞0.461(3N5)＞0.459(2N8),呈现出纯铁晶粒Schmid因子总和平均值随纯度增大的趋势;根据Schmid定律可知,4N3纯铁的织构特征最有利于其变形。综上所述,在本工作中,随着纯铁纯度由2N8提升至4N3,样品中杂质原子减少,促进了4N3高纯铁产生强烈的〈113〉|X和γ织构特征以及利于材料力学性能各向异性的{332}〈113〉织构,增大了其晶粒Schmid因子总和平均值。     

退火工艺对DC04汽车板再结晶组织和织构的影响

以酒钢CSP工艺DC04冷轧汽车板为原料,通过实验室模拟退火工艺,采用OM、EBSD、ODF技术,研究退火工艺对其组织和织构特征的影响。结果表明,DC04汽车板退火组织为铁素体和少量渗碳体,575℃退火1h再结晶开始,730℃退火1h后再结晶较为充分,并随着退火时间的延长,铁素体晶粒长大。不同压下率的DC04冷轧板和退火板中,主要织构均为bcc金属中典型的α(<110>//RD)纤维织构和γ（<111>//ND）纤维织构。随着压下率增加,{111}<112>织构的取向密度明显大于{111}<110>织构的取向密度。730 ℃退火后,低压下率67%的退火板织构中有微弱的{001}<110>取向,但随着压下率增大,这种织构逐渐消失,而形成较强的{111}<112>、{111}<110>有利织构。增加变形量有利于获得有利的{111}织构而抑制不利{001}织构的生成,从而提高DC04的深冲性能。     

Investigation of the orientation dependence of recovery in low-carbon steel by use of single orientation determination

Iron poly- and oligocrystals with a carbon mass content of 0.02 % were cold rolled to a technical strain () of 90 % and annealed at 1000 K in a salt bath furnace for 1 to 300 s. The polycrystals had an initial grain size of about 20 μm. The oligocrystals consisted of 20–40 grains with a longitudinal extension of 10–20 mm and a transverse extension of 2–6 mm. The microstructure of both types of specimens was investigated by use of optical and scanning electron microscopy. The crystallographic texture was examined by use of X-ray and electron back scattering diffraction. It is shown that both primary recrystallization and recovery considerably depend on the crystal orientation. In the 90 % cold rolled oligocrystals {111} uvw and {112}<110> oriented grains recrystallized during annealing. In crystals with {001 }<110> orientation, however, primary recrystallization was suppressed. In the polycrystals the latter phenomenon was less pronounced. In these samples it was observed that {001 }<110> oriented grains are consumed by growing nuclei stemming from neighbouring crystals.     

Fracture of single crystals of the nickel-base superalloy PWA 1480E in hydrogen at 22 °C

The hydrogen-induced fracture behavior of notched single crystals of the PWA 1480E nickel-based superalloy was studied. Notched single crystals with seven different crystal orientations near [100], [110], [111], [013], [112], [123], and [223] were tensile tested at 22 °C in an hydrogen atmosphere at 34 MPa. The notch tensile strength degradation in hydrogen was orientation dependent. The specimen with the [100] orientation had the greatest strength degradation, while the crystal with the [111] orientation had the least. A stereoscopic technique combined with the use of planar γ′ morphologies was applied to identify cleavage plane orientations. All specimens failed predominately by {100}-type cleavage within about 0.5 mm of the notch and {111}-type cleavage toward the center of the crystal. Cleavage on {111}-type planes in the center of the crystals was not related to testing in hydrogen. Microcracking along the {100} γ/γ′ interfaces was observed in the area near the fractured surface. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies indicated that {100}-type cleavage within the notch region controlled the hydrogen-induced cleavage fracture in notched single crystals. Formerly graduate Student, Auburn University     

The Formation of the {112}<111> Shear Texture in Hot-Rolled Sheets of Electrical Steels

Due to the friction between rolls and sheet surface, shear texture inevitably occurs in the surface layer of the hot-rolled sheets in electrical steel. The shear texture contains Goss texture {110}<001>, brass texture {110}<112>, and copper texture {112}<111>. The existence of shear texture and its corresponding microstructure affect the texture distribution in the subsequent normalized sheets, cold-rolled sheets, and final sheets. Electron backscattered diffraction and reaction stress model are used herein to study the formation conditions of {112}<111> orientation in the hot-rolled sheets. The results show that initial rotated cube orientation tends to rotate around transverse direction to the copper orientation during hot rolling due to the shear action. Different shear orientations can be formed in different regions of an initial coarse columnar grain during hot rolling, because of the change in surrounding environment reaction and the difference of the shear strain at different thickness positions. The thinner the hot-rolled sheet is, the smaller the dynamic recrystallization region with shear orientation, and there is almost no copper texture in the thinnest hot-rolled sheet. The simulation results show that the copper texture is easy to form under the action of σ₂₃ and σ₂₂ reaction stresses.