CoCrFeMnNi高熵合金冷轧及退火后的晶界特征

采用电子背散射衍射（EBSD）技术研究了冷轧变形（90%）CoCrFeMnNi高熵合金在800 °C退火再结晶过程中的晶界特征分布（GBCD）。结果表明,退火0.08 h后,合金发生初次再结晶,组织中形成高达56.92%的低å重合位置点阵（CSL）晶界,其中å3晶界和å9+å27晶界的比例分别为53.04%和2.12%,且大部分低åCSL晶界处于大角度晶界网络上,打破了大角度晶界网络连通性,其GBCD得到优化。延长退火时间（0.08～10 h）,合金晶粒异常长大至二次再结晶完成,强a-{110}织构所占体积分数从49.53%增大至66.65%;低åCSL晶界的总比例和å3晶界的比例均下降,å9+å27晶界比例先上升后下降,大角度晶界网络连通性逐渐趋于完整。与此同时,该合金的维氏硬度与其再结晶晶粒尺寸满足Hall-Petch关系。     

CoCrFeMnNi高熵合金冷轧及退火后的晶界特征分布

采用电子背散射衍射(EBSD)技术研究了冷轧变形(90%)CoCrFeMnNi高熵合金在800℃退火再结晶过程中的晶界特征分布(GBCD)。结果表明,退火0.08 h后,合金发生初次再结晶,组织中形成高达56.92%的低∑重合位置点阵(CSL)晶界,其中∑3晶界和∑9+∑27晶界的比例分别为53.04%和2.12%,且大部分低∑CSL晶界处于大角度晶界网络上,打破了大角度晶界网络连通性,其GBCD得到优化。延长退火时间(0.08~10 h),合金晶粒异常长大至二次再结晶完成,强α-{110}织构所占体积分数从49.53%增大至66.65%;低∑CSL晶界的总比例和∑3晶界的比例均下降,∑9+∑27晶界比例先上升后下降,大角度晶界网络连通性逐渐趋于完整。与此同时,该合金的维氏硬度与其再结晶晶粒尺寸满足Hall-Petch关系。     

Annealing behaviour of cold rolled aluminum alloy in a high magnetic field

The crystallographic texture evolution of cold rolled (71%) aluminum alloy 3103 was investigated during annealing at 290 °C in a magnetic field of 19 T. The analysis reveals that texture and microstructure evolution in this material can be affected by a magnetic field which manifests itself in enhanced recovery and an earlier start of subsequent primary recrystallization.     

Recovery and recrystallization in commercial purity aluminum cold rolled to an ultrahigh strain

Recovery and recrystallization were studied in commercial purity aluminum cold rolled to an ultrahigh strain (ε_vM = 6.4) and isothermally annealed at 300 °C. The deformed material consists of three layers with similar fractions of high-angle boundaries (HABs) and similar lamellar boundary spacings, but with different textures and different spatial arrangements of the rolling texture components. Annealing leads initially to a coarsening of the lamellar microstructure, accompanied by a reduction in the HAB fraction. Ex-situ experiments using very short annealing times indicate that such microstructural changes are consistent with a process of coarsening via triple junction motion. The recovery proceeds similarly in the center and subsurface layers, but because of the different initial spatial arrangement of the texture components in these layers, the loss of HABs is significantly greater in the subsurface compared with the center layer. Further annealing leads to discontinuous recrystallization, which occurs differently in the center and subsurface layers. In the center layer, recrystallization proceeds more rapidly and with a larger frequency of nuclei, resulting in a smaller recrystallized grain size. In contrast, pronounced recrystallization in the subsurface layers is delayed, and the recrystallized grain size is larger than in the center. It is concluded that the changes taking place during recovery are very significant in determining the subsequent recrystallization behavior in terms of the final grain size and texture.     

A quantitative analysis of the evolution of texture and stored energy during annealing of cold rolled copper

The experimental evolution of the global texture during recrystallization of cold rolled copper is presented after various rolling reductions. After presentation of the method used for the decomposition of the orientation distribution functions obtained from X-ray diffraction measurements into gaussian peaks, the behavior of each texture component is studied. This quantitative analysis coupled with stored energy measurements also obtained by X-ray diffraction allows the oriented nucleation and growth mechanisms to be linked to stored energy variations. The proposed mechanisms are then confirmed by local observations obtained by EBSD.     

时效+再结晶退火对镍基合金锻造混晶组织的影响

为了消减镍基合金锻件中的混晶组织,本文提出了δ相时效+再结晶退火的热处理工艺路线。δ相在时效过程中可以直接析出或者由γ″相发生相变间接析出。对含析出δ相的材料进行高温再结晶退火,然后立即水冷,可以发现时效方式和时效时间对退火过程中的组织演变存在显著影响。时效过程中直接析出的δ相主要分布在晶界,随着时效时间延长部分晶粒内部也会析出δ相,其形貌以短棒状为主。间接析出的δ相主要分布在晶粒内部以及晶界,其形貌主要为晶内长针状以及晶界短棒状。短棒状δ相在退火过程中与位错交互作用较弱,主要起到钉扎晶界的作用;而长针状δ相能够促使亚晶的形成。因此,间接时效方式有利于再结晶形核的发生,并能够有效阻碍晶粒生长避免异常长大的再结晶晶粒。     

On the influence of small quantities of Bi and Sb on the evolution of microstructure during swaging and heat treatments in copper

In the present work, the influence of small amounts of Bi and Sb on the microstructural evolution of Cu during an ingot metallurgy processing route is investigated. Both elements are known to segregate to grain boundaries in Cu. Cu ingots with an outer diameter of 40 mm containing 0.008 wt.% Bi and 0.92 wt.% Sb, respectively, were vacuum induction melted, cast, and gradually swaged down to a final diameter of 11.7 mm with several intermediate annealing steps. Subsequent annealing treatments were conducted to investigate the microstructural evolution of the swaged bars. Optical microscopy, hardness testing and orientation imaging microscopy were used to characterize the deformation and recrystallization behavior, as well as the evolution of texture in the alloys. The results are then compared to those obtained for pure Cu. It is shown that even small amounts of alloying elements significantly alter the hardening behavior and suppress recrystallization at low temperatures. At higher temperatures, recrystallization in Cu, Cu-Bi and Cu-Sb leads to different textures.     

Hi-B钢二次再结晶退火过程中未异常长大Goss晶粒晶界特征

采用中断法并结合电子背散射衍射(EBSD)技术,研究了Hi-B钢二次再结晶退火过程中大量未异常长大Goss取向晶粒的晶界特征。结果表明:未异常长大Goss取向晶粒的晶粒尺寸相较于基体晶粒和相邻晶粒并没有明显的差异性。同时未异常长大Goss取向晶粒与异常长大Goss取向晶粒周围的HE晶界和CSL晶界比例也没有明显的差异。在二次再结晶退火过程中,尺寸优势、HE晶界、CSL晶界和Goss取向偏离度都不能保证Goss取向晶粒发生异常长大。而随着退火温度的升高,Goss取向晶粒有逐渐向标准Goss晶粒取向靠拢的趋势。     

Grain refinement and boundary misorientation transition by annealing in the laser rapid solidified 6FeNiCoCrAlTiSi multicomponent ferrous alloy coating

A 6FeNiCoCrAlTiSi multicomponent ferrous alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. Grain boundary misorientation transition and abnormal microstructure refinement in the coating after annealing at 500 °C have been studied by electron backscatter diffraction (EBSD) observation. Before annealing, the microstructure of the coating is mainly composed of directionally solidified columnar grains with low angle grain boundaries distributed as networks. After annealing, the main phase and microhardness of the coating almost remain unchanged. However, the columnar grains transform to equiaxed refined grains with the grain boundary misorientation transition from low to high angles. This result supports such an argument that the reheating process in post-stage of solidification plays a key role on the grain refinement during rapid solidification process.     

Effect of thermal annealing on microstructure and mechanical properties of a gradient structured tantalum prepared by plasma activated sintering

Fully dense bulk tantalum compacts of two different nitrogen contents with gradient structure within an individual particle were successfully synthesized by means of plasma activated sintering (PAS). Annealing of the compacts induces disappearing of the gradient structure due to the promoted diffusion of nitrogen in Ta matrix accompanied by enhancement of the strength. For the compact with low nitrogen content of 0.09 wt.%, a drop in ductility was observed. While for the compact with nitrogen content of 0.215 wt.%, improved strength was obtained without sacrificing its ductility.     

Linking recovery and recrystallization through triple junction motion in aluminum cold rolled to a large strain

Recovery mechanisms and kinetics have been studied in commercial purity aluminum (AA1050) cold rolled to a true strain of 5.5 (99.6% thickness reduction) and annealed at low temperatures from 140 to 220 °C. Transmission electron microscopy, electron backscatter diffraction (EBSD) and electron channeling contrast (ECC) are used to characterize the microstructural evolution during annealing. The microstructural characterization shows that a deformed lamellar structure coarsens uniformly during annealing by triple junction motion while maintaining the lamellar morphology, leading to a gradual transition into a more equiaxed structure, where recrystallization nuclei start to evolve. The apparent activation energy for the microstructural coarsening is estimated separately for different stages characterized by an increase in the lamellar boundary spacing measured by EBSD and ECC. The apparent activation energy increases during annealing, from 110 kJ mol^?1 at the beginning to 230–240 kJ mol^?1 at the end of uniform coarsening, linking the recovery stages to recrystallization. The increase in activation energy underpins operation of different diffusion mechanisms for migration of boundaries and their junctions during coarsening, and solute drag may become increasingly important as the structure coarsens. These findings form the basis for a discussion of the thermal behavior of a fine lamellar structure produced by cold rolling to a large strain of both scientific and applied interest.     

Cube recrystallization textures in a hot deformed Al–Mg–Si alloy

The formation of cube recrystallization textures has been studied on Al–Mg–Si polycrystals deformed at 400 °C by channel die compression tests and annealed at 510 °C. A cube recrystallization texture was observed on samples presenting a very low fraction of cube volumes before and after deformation.     

430冷轧带钢退火过程的晶粒长大及其对织构的影响

试验研究了430不锈钢冷轧带钢等温退火过程中的晶粒长大规律及其对再结晶织构的影响。利用截线法测量了不同退火情况下的晶粒尺寸,并对其演变规律进行了定量分析;通过ODF图来分析晶粒长大过程中薄板内部晶粒宏观取向的变化。研究发现,低于850 ℃晶粒长大不明显; 875 ℃时晶粒长大较为明显,其长大过程主要集中在30 min时间;890 ℃退火长时间保温后冷却,材料内有马氏体生成;建立了430铁素体不锈钢晶粒长大动力学方程,晶粒长大指数和激活能分别为8.44和531.54 kJ/mol;晶粒长大过程储能较高的织构体积分数减弱,而储能较低的织构体积分数则变强。     

罩式炉退火过程中温度对08Al冷轧钢带再结晶的影响

以试验为基础,对同一罩式炉炉台冷轧08A l钢带的退火周期进行多点温度测量。分析退火温度对再结晶的影响。得出各阶段钢卷温度分布规律：钢卷退火时卷心和外圈为热点,卷中部为冷点,为了保证钢带良好的冲压性能,要适当调整罩式炉的加热速度和保温时间。     

Effect of hot and cold deformation on the P {0 1 1}4 5 5 recrystallization texture in a continuous cast Al–Mn–Mg aluminum alloy

The effect of different relative amounts of hot and cold deformation on the P {0 1 1}4 5 5 recrystallization texture in a continuous cast Al–Mn–Mg aluminum alloy was investigated by X-ray diffraction. The results show that at a given total rolling strain the sheet with a high hot rolling strain exhibits a significantly stronger P texture than the sheet with a low hot rolling strain. Hot deformation strongly promotes the formation of the P texture during recrystallization annealing.     

含锡取向硅钢高温二次再结晶退火过程中抑制剂的析出特点

采用透射电镜研究了含锡取向硅钢高温二次再结晶退火过程中抑制剂的析出行为,分析了抑制剂对初次再结晶的抑制作用。结果表明,析出物除了常规的AlN和MnS外,还有少量Sn单质;其中AlN和MnS相是主要抑制剂,具有强烈的抑制作用;少量Sn相起辅助抑制作用,控制析出物AlN的尺寸和数量,有助于主抑制剂的弥散分布。抑制剂在600~700 ℃时开始析出长大,900 ℃显著长大,1020 ℃平均尺寸达到最大值;抑制剂的尺寸随退火温度升高而增大,体积分数、分布密度则先增大后减少。当退火温度达到1000 ℃时,析出物平均粒径约50.3 nm,体积分数最大约3.81%,分布密度约5.9×10¹⁴ 个/cm³。根据试验和Zener因子综合判定抑制力,Zener因子随退火温度升高而增加,在900 ℃达到最大139,析出物分布密度达到最大8.9×10¹⁴个/cm³;在1020 ℃时,Zener因子几乎为零,完成二次再结晶过程。     

Strong morphological and crystallographic texture and resulting yield strength anisotropy in selective laser melted tantalum

Selective laser melting (SLM) makes use of a high energy density laser beam to melt successive layers of metallic powders in order to create functional parts. The energy density of the laser is high enough to melt refractory metals like Ta and produce mechanically sound parts. Furthermore, the localized heat input causes a strong directional cooling and solidification. Epitaxial growth due to partial remelting of the previous layer, competitive growth mechanism and a specific global direction of heat flow during SLM of Ta result in the formation of long columnar grains with a 〈1 1 1〉 preferential crystal orientation along the building direction. The microstructure was visualized using both optical and scanning electron microscopy equipped with electron backscattered diffraction and the global crystallographic texture was measured using X-ray diffraction. The thermal profile around the melt pool was modeled using a pragmatic model for SLM. Furthermore, rotation of the scanning direction between different layers was seen to promote the competitive growth. As a result, the texture strength increased to as large as 4.7 for rotating the scanning direction 90° every layer. By comparison of the yield strength measured by compression tests in different orientations and the averaged Taylor factor calculated using the viscoplastic self-consistent model, it was found that both the morphological and crystallographic texture observed in SLM Ta contribute to yield strength anisotropy.     

弥散相对铝合金冷轧过程中晶粒分裂和织构演变的影响

制备了2种含有相近合金元素含量但不同的弥散第二相密度的铝锰合金冷轧板材。利用背散射电子衍射和取向成像图技术研究了晶粒分裂和微观织构,使用X射线衍射技术测量了宏观织构。研究发现当应变达到3左右时,高密度的小尺寸弥散相会促进铜型和S型织构的形成,同时增加了大角晶界所占比例。在小应变下,弥散相对织构和大角晶界的影响不显著。研究显示弥散相通过钉扎晶界从而促进织构演化,进而影响晶粒分裂和大角晶界的形成。