中温含铜取向硅钢的形变和再结晶织构特征

通过对比中温含铜取向硅钢与普通取向硅钢和高磁感取向硅钢的组织和织构特征,分析中温含铜取向硅钢独特的织构演变规律及其对二次再结晶行为的影响。结果表明,为了获得有利于高斯晶粒长大的强γ取向线织构,中温含铜钢需经过回复退火处理和高温退火阶段慢速升温。回复过程中γ取向线晶粒储能降低,同时慢速升温有利于γ取向线晶粒的形核和再结晶。中温含铜钢的二次再结晶开始温度超过1000益,由于初次再结晶晶粒组织以γ织构为主且非γ取向线晶粒较少,导致最终二次晶粒尺寸超大且晶界圆滑,二次再结晶机理以择优长大为主导,超大的二次晶粒尺寸导致最终成品的铁损升高,但通过激光刻痕处理后,整体铁损的降低效果比二次晶粒较小的高磁感取向硅钢更加显著。     

高纯铝定向凝固中晶粒的生K特性

采用自制的定向凝固提纯炉定向制备了大直径高纯铝圆锭,并对其定向凝固组织中晶粒的生长状况进行了研究.结果表明,初生的高纯铝晶粒易于发生再结晶合并,随着保温时间的增加,晶粒的生长形态逐渐由等轴晶态转变为柱状晶态;过渡区晶粒在晶界夹角处形核,并在随后的竞争生长过程中产生湮没、扭转等状况;多晶生长暂停拉伸时,新晶粒将在柱状晶顶部晶界夹角处形核并长大,而且新晶粒的晶格取向与原有晶粒的取向无关.     

冷轧工艺对取向硅钢初次再结晶织构的影响

研究了取向硅钢制备过程中常见的两种冷轧工艺,主要研究了一阶段冷轧与两阶段冷轧+中间退火工艺对初次再结晶组织及织构的影响.结果表明:采用两阶段冷轧+中间退火工艺制备以Cu2S为主抑制剂的取向硅钢,其初次再结晶平均晶粒尺寸为181μm,高斯晶粒的体积分数为06%,迁移性强的重位点阵晶界(Σ5+Σ9)和高能晶界(20°~45°取向偏差角)所占比例分别为18%和504%.与一阶段冷轧工艺相比,其初次再结晶晶粒较细,且高斯晶核与特征晶界所占的比例较高,有利于高斯晶粒发生二次再结晶.     

高纯铝定向凝固中晶粒的生长特性

采用自制的定向凝固提纯炉定向制备了大直径高纯铝圆锭，并对其定向凝固组织中晶粒的生长状况进行了研究．结果表明，初生的高纯铝晶粒易于发生再结晶合并，随着保温时间的增加，晶粒的生长形态逐渐由等轴晶态转变为柱状晶态；过渡区晶粒在晶界夹角处形核，并在随后的竞争生长过程中产生湮没、扭转等状况；多晶生长暂停拉伸时，新晶粒将在柱状晶顶部晶界夹角处形核并长大，而且新晶粒的晶格取向与原有晶粒的取向无关．     

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。     

低温高磁感取向硅钢高温退火过程高斯晶粒的演变

对低温加热工艺生产的以AlN为主抑制剂的高磁感取向硅钢高温退火过程进行中断实验,借助电子背散射衍射技术对高温退火过程中高斯晶粒的演变进行了研究.在升温过程中高斯晶粒平均尺寸先减小再增大.800℃时取向分布函数图出现高斯织构组分,但强度很弱,高斯晶粒偏离角在10°以上;900℃时高斯晶粒平均生长速率超过其他晶粒;950~1000℃时高斯晶粒异常长大,偏离角3°~6°;在1000℃之前高斯取向晶粒相比于其他晶粒没有尺寸优势.     

Q235碳素钢不同热变形条件下退火过程的织构分析

利用扫描电镜、背散射电子衍射(EBXD)和X射线衍射技术研究了三种方式热变形后保温时铁素体的长大行为.结果表明,回复、再结晶和长大的相对程度与第二相粒子的状态及铁素体的取向分布有关.形变强化相变产生的超细铁素体中形变储存能较低,退火时难以发生静态再结晶,而以晶粒长大为主,铁素体因第二相出现较晚而充分生长:A1温度以下纯铁素体区形变的铁素体虽然形变储存能最高,形变量最大,但第二相钉扎最明显,铁素体仅发生部分再结晶,<111>取向形变晶粒比<100>取向形变晶粒更明显地被削弱;α+γ两相区形变时,铁素体(亚)晶粒发生回复式长大,<111>取向晶粒和<100>取向晶粒有不同的再结晶倾向.     

薄带连铸取向硅钢的热轧孪生行为

薄带连铸流程下取向硅钢粗大λ晶粒(〈100〉//ND,normal direction)的“遗传”会导致磁性能恶化.为解决这一问题,针对取向硅钢的热轧孪生行为开展研究,结果表明:凝固组织粗大的取向硅钢在650℃热轧时可产生大量112〈111〉形变孪晶,这与具有高层错能的硅钢在较高温度下难以孪生变形的传统认知不同.热轧过程中复杂的应力状态降低了变形孪晶的取向依赖性,由于具有更高的储存能,孪晶界/孪晶界及孪晶界/晶界交叉点成为再结晶形核的优先位置,大大提高了常化过程中的再结晶率,受沿孪晶界应变分布及孪晶间距离的限制,沿孪晶界形核的再结晶晶粒通常呈“饼状”,最终形成以细小且取向漫散的再结晶晶粒为主的常化组织,消除了初始凝固组织中有害的粗大λ晶粒.     

相场法研究初始微结构对晶粒长大的影响

【目的】研究不同初始微结构对晶粒长大过程及生长动力学的影响。【方法】采用相场法(Phase Field)模拟二维多晶材料中正常晶粒长大及初态分别为柱状和梯度微结构的晶粒长大过程。【结果】正常晶粒长大的相对晶粒尺寸分布具有时间不变性的特点;柱状微结构的长宽比和梯度微结构的梯度指数均直接影响晶粒长大动力学,这两种初始微结构在演化过程中均向均匀等轴微结构转变。【结论】晶粒长大是大晶粒不断吞噬相邻小晶粒的过程;晶界曲率对晶粒长大过程有显著影响,曲率越大,晶粒长大越快。     

金属再结晶过程中晶粒取向差分布的统计计算方法

从取向分布函数的基本概念出发，提出了统计计算晶界两侧晶粒取向差分布规律的方法，利用这种方法不仅可以计算晶粒取向随机分布时晶粒之间取向差的分布，而且可以计算具有织构的条件下，再结晶晶粒与形变基体之间晶界两内晶粒的取向差的分布规律，在计算过程中可以直接代入实际测算的ＯＤＦ数据进行计算。     

Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe-Ga rolled alloys

The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1at% NbC-doped Fe₈₃Ga₁₇ alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300℃ and 12.0% at 500℃ of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300℃ and 46.6% at 500℃. In the slabs for rolling, the introduction of <001>-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.     

Influence of MnS particles on the behaviors of grain boundary migration in Fe-3%Si alloys

The precipitation behaviors of MnS particles at 900℃ in a hot deformed Fe-3%Si alloy were observed statistically. The ratio of MnS particles on dislocations and in grain boundaries was calculated based on a model concerning the second phase precipitation in supersaturated solid solution. It was indicated that the precipitation of MnS particles on dislocations prevailed. The coarsening process of MnS particles in grain boundaries determined the boundary mobility during the secondary recrystallization. However, the density difference of precipitated MnS particles inside the grains on both sides of a boundary will determine the migration direction of the boundary as well, besides the grain size effect. It was observed that the densities of MnS particles in two neighboring grains were commonly different, and the boundary tended to move towards the area with lower particle density. The factors, e.g. dislocation densities in differently oriented grains will affect the density of precipitated particles, in which the Goss grains with higher particle density could grow more easily.     

Simulation of recrystallization based on EBSD data using a modified Monte Carlo model that considers anisotropic effects in cold-rolled ultra-thin grain-oriented silicon steel

A Monte Carlo Potts model was developed to simulate the recrystallization process of a cold-rolled ultra-thin grain-oriented silicon steel. The orientation and image quality data from electron backscatter diffraction measurements were used as input information for simulation.Three types of nucleation mechanisms, namely, random nucleation, high-stored-energy site nucleation(HSEN), and high-angle boundary nucleation(HABN), were considered for simulation. In particular, the nucleation and growth behaviors of Goss-oriented({011}100) grains were investigated. Results showed that Goss grains had a nucleation advantage in HSEN and HABN. The amount of Goss grains was the highest according to HABN, and it matched the experimental measurement. However, Goss grains lacked a size advantage across all mechanisms during the recrystallization process.     

轧制Fe_(81)Ga_(19)合金薄带再结晶织构演变

对Fe_(81)Ga_(19)合金进行冷轧与再结晶退火,考察了压下率对再结晶织构及磁致伸缩性能的影响.再结晶织构主要由Goss({110}001)和γ(111//ND)织构组成,再结晶织构特征随压下率增加出现明显的改变,归因于变形微结构与冷轧织构的差异.冷轧压下率从60%增加到70%时,剪切带密度增加且{111}112形变织构增强,提高再结晶Goss织构强度与磁致伸缩性能.压下率为80%时,剪切带与形变基体取向变化使剪切带晶核取向漫散,且晶界储能提高为再结晶γ织构提供更多形核位置,导致再结晶Goss织构减弱而γ织构增强,降低薄带磁致伸缩性能.     

薄板坯连铸连轧工艺下Hi-B钢的组织及织构

采用金相显微镜和扫描电镜研究实验室模拟薄板坯连铸连轧( TSCR)工艺试制的高磁感取向硅钢( Hi- B钢)组织、织构的演变特征. 研究发现实验室模拟薄板坯连铸连轧工艺试制的Hi-B钢热轧板显微组织及织构在厚度方向上存在不均匀性. 常化板表面脱碳层铁素体晶粒明显粗化,常化板织构基本继承了热轧板相应的织构类型,仅织构强度不同. 一次大压下率冷轧后,晶粒及其晶界沿轧向被拉长形成鲜明的纤维组织,织构主要为α纤维织构和γ纤维织构,脱碳退火后试样发生回复和再结晶现象并形成初次晶粒组织,脱碳退火后织构分布较为集中. 温度升高至1000℃时二次再结晶开始,1010℃时钢中晶粒发生异常长大,高斯织构强度达到61. 779. 成品磁感为1. 915 T,铁损为1. 067 W·kg-1 .     

Monte Carlo study on abnormal growth of Goss grains in Fe-3%Si steel induced by second-phase particles

The selective abnormal growth of Goss grains in magnetic sheets of Fe-3%Si (grade Hi-B) induced by second-phase particles (AlN and MnS) was studied using a modified Monte Carlo Potts model. The starting microstructures for the simulations were generated from electron backscatter diffraction (EBSD) orientation imaging maps of recrystallized samples. In the simulation, second-phase particles were assumed to be randomly distributed in the initial microstructures and the Zener drag effect of particles on Goss grain boundaries was assumed to be selectively invalid because of the unique properties of Goss grain boundaries. The simulation results suggest that normal growth of the matrix grains stagnates because of the pinning effect of particles on their boundaries. During the onset of abnormal grain growth, some Goss grains with concave boundaries in the initial microstructure grow fast abnormally and other Goss grains with convex boundaries shrink and eventually disappear.     

4J29膨胀合金晶粒长大倾向的研究

针对在电子器件中常作为密封材料的4J29合金在生产时出现粗大晶粒造成工件开裂问题,采用热处理和单因素优选实验方法研究4J29合金的再结晶温度、预先变形率与晶粒度之间的关系。研究表明,4J29膨胀合金晶粒聚集长大是由大于70%预先变形率所造成。在实际生产中尽可能采用合理的预先变形率可以提高材料的再结晶温度和二次再结晶温度,可以防止合金晶粒聚集长大,从而保证了工件质量和使用性能。