Phase formation,texture evolutions,and mechanical behaviors of Al0.5CoCr0.8FeNi2.5V0.2 high-entropy alloys upon cold rolling

The cold rolling (CR) reduction dependence of microstructure evolutions and mechanical properties for Al_0.5CoCr_0.8FeNi_2.5V_0.2 high-entropy alloy (HEA) were investigated. The HEA remains FCC structures consisting of nanoscale ordered L1₂ phase, confirming the phase formation prediction. With increasing CR reduction, the textures transform from random ones to FCC rolling ones accompanied by dense slip bands and deformation twins. Under a 50% CR reduction, the deformation textures started to become evident and were governed by typical {111}<112>F, {110}<100>Goss and {112}<111>Cu texture components. When the CR reduction approached 90%, the deformation textures mainly contained the {110}<111>A, {114}<110>X, and {112}<111>Cu texture components. As a result, both Vickers hardness and ultimate strength increased, but the ductility decreased roughly. The enhanced strength should be attributed to the anisotropy and work hardening behavior from textures. The plastic deformation for the samples under low CR reductions was dominated by deformation twins and slip bands. However, under high CR reductions, the textures severely impeded the further propagation of pre-existing slip bands, leading to the rapid decrease of ductility. Therefore, the CR reduction should be carefully designed before optimal heat treatments to enhance the strength and ductility synergy.     

纳米银枝晶的电沉积及结构表征

采用恒电位电沉积法,选择十二烷基磺酸钠(SDS)为表面活性剂,在Ti基体上制备了具有树枝状结构的纳米银。X-射线衍射试验表明银纳米枝状体为单晶结构,属于面心立方晶系。运用扫描电镜对枝晶的形貌特征进行观察分析,通过高分辨透射电子显微术对枝晶的晶格结构进行表征,发现枝晶表面由{111}晶面组成,主干和分支互成60°分别沿110方向生长,枝晶的{111}晶面形成多次孪晶结构。树枝状晶体形态的产生符合分形生长机理。     

异步轧制无取向硅钢的再结晶织构演变

在无取向硅钢冷轧过程中采用同步轧制和速比为1.06,1.125,1.19的异步轧制,以考察异步轧制对冷轧和再结晶织构的影响.研究发现,异步轧制减弱冷轧织构中{001}～{112}〈110〉组分,增强{111}〈112〉并减弱{111}〈110〉组分.{111}〈112〉和{111}～{225}〈110〉形变晶粒内剪切带处分别形成η(〈001〉∥RD)及偏离其15°的η′(Ψ=75°,θ=0～45°,φ=0°)再结晶晶粒,η′因晶核尺寸优势发展成为主要织构组分.异步轧制下形变织构的变化有利于改善再结晶织构特征及性能,其影响随速比增大而增强.     

冷轧钢板变形织构的理论模拟

采用取向分布函数法研究了钢板中的轧制织构。其中以｛１１０｝＜１１１＞滑移系滑移为基本变形机制，利用Ｓａｃｈｓ，Ｔａｙｌｏｒ，ＲＣ和ＰＣ等模型对轧制织构进了理论模拟。这些理论模型可以再现体心立方金属冷轧过程中晶粒取向在｛１１２｝＜１１０＞，｛１１１｝＜１１０＞，｛１１１｝＜１１２＞及｛００１｝＜１１０＞附近的聚集过程。分析表明｛１１０｝＜１１１＞滑移系的滑移是体心立方金属十分重要的变形机制，适当参考     

Anatase TiO2 single crystals with a large percentage of reactive facets

Owing to their scientific and technological importance, inorganic single crystals with highly reactive surfaces have long been studied. Unfortunately, surfaces with high reactivity usually diminish rapidly during the crystal growth process as a result of the minimization of surface energy. A typical example is titanium dioxide (TiO2), which has promising energy and environmental applications. Most available anatase TiO(2) crystals are dominated by the thermodynamically stable {101} facets (more than 94 per cent, according to the Wulff construction), rather than the much more reactive {001} facets. Here we demonstrate that for fluorine-terminated surfaces this relative stability is reversed: {001} is energetically preferable to {101}. We explored this effect systematically for a range of non-metallic adsorbate atoms by first-principle quantum chemical calculations. On the basis of theoretical predictions, we have synthesized uniform anatase TiO(2) single crystals with a high percentage (47 per cent) of {001} facets using hydrofluoric acid as a morphology controlling agent. Moreover, the fluorated surface of anatase single crystals can easily be cleaned using heat treatment to render a fluorine-free surface without altering the crystal structure and morphology.     

Influence of slip system combination models on crystal plasticity finite element simulation of NiTi shape memory alloy undergoing uniaxial compression

The influence of various slip system combination models on crystal plasticity finite element simulation of Ni Ti shape memory alloy subjected to uniaxial compression deformation is investigated according to three combinations of slip systems, including combination of {010}100and {110}111slip modes, combination of {110}100and {110}111slip modes and combination of {110}100, {010}100and {110}111slip modes, which consist of 18, 18 and 24 slip systems, respectively. By means of simulating mechanical response,strain distribution, stress distribution and Schmid factor, it can be found that in terms of simulation accuracy,combination of {110}100and {110}111slip modes is in good agreement with combination of {110}100,{010}100and {110}111slip modes. The contribution of {110}100slip mode to plastic strain is primary in plastic deformation of Ni Ti shape memory alloy, whereas {010}100slip mode, which makes small contribution to plastic deformation, can be regarded as the unfavorable slip mode. In the case of large plastic strain, the {010}100slip mode contributes to the formation of(001) [010] texture component, while {110}100and {110}111slip modes facilitate the formation of γ-fibre(111) texture.     

Microstructure and texture evolution of a near β titanium alloy Ti-7333 during continuous cooling hot deformation

The microstructure and texture evolution during continuous cooling hot deformation(CCHD) in a near β titanium alloy, named Ti-7Mo-3Nb-3Cr-3Al(Ti-7333), were investigated by using the electron backscattered diffraction(EBSD). The results indicate that the precipitation of secondary α phase was restricted by CCHD, and the morphology of primary α phase nearly had no change with the deformation and temperature drop. In contrast, βphase underwent more deformation and the grains tended to refine. This may be due to the dynamic recrystallization(DRX) of β phase, including continuous dynamic recrystallization(CDRX) and discontinuous dynamic recrystallization(DDRX). In addition, the textures of {110} 110 , {225} 520 and{115} 123 transformed to {100} 110 and {001} 100 during CCHD. Among these, the η-fiber component of {001} 100 was the dominant deformation texture in the deformed Ti-7333 alloy. Finally,continuous cooling has an important effect on the work hardening and softening during CCHD, contributing to the different flow behaviors at different cooling rates.     

Observation of Pt-{100}-p(2×2)-O reconstruction by an environmental TEM

The surface structure of noble metal nanoparticles usually plays a crucial role during the catalytic process in the fields of energy and environment. It has been studied extensively by surface analytic methods, such as scanning tunneling microscopy. However, it is still challenging to secure a direct observation of the structural evolution of surfaces of nanocatalysts in reaction(gas and heating) conditions at the atomic scale. Here we report an in-situ observation of atomic reconstruction on Pt {100} surfaces exposed to oxygen in an environmental transmission electron microscope(TEM). Our high-resolution TEM images revealed that Pt-{100}-p(2×2)-O reconstruction occurs during the reaction between oxygen atoms and{100} facets. A reconstruction model was proposed, and TEM images simulated according to this model with different defocus values match the experimental results well.     

High temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at1100 ℃. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.     

加权的~Coxeter~群~$\widetilde{\bm C}_{\bm n}$~的左胞腔

仿射~Weyl~群~($\widetilde{A}_{2n},\widetilde{S}$)
在某个群同构~$\alpha$~(其中~$\alpha(\widetilde{S}) =
\widetilde{S}$)~下的固定点集合
能被看作是仿射~Weyl~群~($\widetilde{C}_n,S$). 那么加权的~Coxeter~群\
($\widetilde{C}_n,\widetilde{\ell}$)的左和双边胞腔($\widetilde{\ell}$
是仿射~Weyl~群~$\widetilde{A}_{2n}$~的长度函数),
就能通过研究仿射~Weyl~群~($\widetilde{A}_{2n},\widetilde{S}$)
在群同构~$\alpha$~下的固定点集合而给出一个清晰的划分.
因此给出了加权的~Coxeter~群~($\widetilde{C}_n,\widetilde{\ell}$)
对应于划分\ $\textbf{k}\textbf{1}^{\textbf{2n+1-k}}$~和~$(2n-1,2)$
的所有左胞腔的清晰刻画, 这里对所有的~$1\leqslant k \leqslant 2n+1$.     

Ti--26Nb--4Zr 合金冷轧板材的织构和力学性能

采用 X 射线衍射和室温拉伸方法研究了冷轧变形和固溶处理对 Ti-26Nb-4Zr 合金板材的织构和力学性能的影响.研究发现,50%冷轧时形成了{001}＜uvw＞织构,随着冷变形量的增加,逐渐形成了{121}＜111＞和{001}＜110＞混合织构,＜110＞方向由与轧制方向垂直转到与轧制方向平行.800℃固溶处理后,随着变形量的增加,{111}＜110＞再结晶织构形成并逐渐增强,但＜110＞方向始终保持与轧制方向平行.由于加工硬化及晶粒细化的作用,导致随着变形量增加,冷轧板材的强度逐渐提高,塑性降低.固溶处理后,由于发生再结晶,使得板材的塑性相比冷轧态明显提高.     

热轧工艺对409L铁素体不锈钢深冲性的影响

对含有单一柱状晶的409L铁素体不锈钢连铸坯,采用不同终轧温度的热轧工艺,由常规热轧转变为温轧,再经过相同后续工艺;较低终轧温度的成品获得了较高rm值和较低△r值.终轧温度的降低使组织演变发生变化:热轧和冷轧组织中晶界和晶内剪切带增多,变形组织被细化、硬化,尤其是中心层附近的粗大带状晶粒;两者的增多又增加了退火过程中的...     

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。     

Ta-7.5％W在退火过程中的组织和织构演变

通过金相组织观察、透射电子显微镜(TEM)及显微硬度测试,研究冷轧变形量为95％的Ta-7.5％W合金箔材在1 050,1 200和1 360℃退火时的组织和性能变化,并采用取向密度函数(ODF)分析在此过程中其织构演变规律.对其实验结果进行研究发现:冷轧态Ta-7.5％W合金硬度为HV 300,经1 360℃退火后硬度迅速减小,说明此时合金已发生回复再结晶.轧制后的Ta-7.5％W合金箔材具有各向异性,在轧面∥{111}取向上形成位错胞亚结构,在轧面∥{100}取向上形成了形变带,冷轧态的主要织构为{001}〈110〉,{112} 〈110〉和{110}〈110〉织构;在1 200℃退火时,在轧面∥{111}取向上,再结晶通过亚晶界迁移、亚晶长大形核,而在轧面∥{100}取向上,主要是通过亚晶转动、聚合形核;{001}〈110〉织构增强,{112}〈110〉织构减弱;在1 360℃退火时,{001}〈110〉织构急剧减弱,{111}〈112〉织构增强.     

单晶铜纳米线弯曲、扭转的变形机制的分子动力学研究

本文利用分子动力学方法研究了〈001〉/{100}和〈110〉/{111}两种单晶铜纳米线在弯曲、扭转载荷作用下的变形机制和力学行为.在〈001〉/{100}铜纳米线的弯曲过程中,当弯曲角度很大时,我们观察到了一些五重变形孪晶.分析表明,配位数为12的其它原子类型与hcp原子类型间的相互转化是导致出现这种五重变形孪晶的重要因素.这个结果与文献（Appl Phys Lett,2006,89：041919）所报道的纳米晶铜在拉伸状态下所观察到的五重变形孪晶的形成过程截然不同;然而该孪生变形机制并未在相应的？110？/{111}单晶铜纳米线的弯曲加载过程中被发现.此外,通过对〈001〉/{100}和？110？/{111}单晶铜纳米线进行扭转模拟,我们发现,这两种纳米线的扭转塑性变形分别是以从表面边角和侧表面发射全位错为主的变形机制.     

Cr元素对冷轧TRIP钢的组织性能影响研究

以两种合金成分的相变诱导塑性钢为实验对象,先利用热模拟试验机确定其热轧及热处理参数后,经过热轧、冷轧工艺并连续退火,研究其力学性能。金相组织及宏观织构的特征。实验结果表明,Cr元素可以稳定低温奥氏体,降低贝氏体形成温度,使贝氏体的孕育期延长,增加最终组织中的贝氏体及残余奥氏体的体积分数;Cr元素的添加还增强了试验钢的力学性能,添加了Cr元素的2#钢强度和塑性均比没有添加的1#钢要高;两种成分的TRIP钢织构情况相似,主要组分包括：{332}纤维织构,{110}<001>组分和{112}<110>组分,可见Cr元素在提高钢板强度增加延伸率的同时,并没有损害钢板的成形性能。     

Microstructure and texture evolution of cold-rolled deep-drawing steel sheet during annealing

In accordance with experimental results about the annealing microstructure and texture of cold-rolled deepdrawing sheet based on the compact strip production (CSP) process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. {111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of {111} advantageous texture components in the annealing texture increases from 55vol% to 65vol%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.     

基于｛XW_（12）O_（40）｝~（4-）（X=Si/Ge）阴离子的二维Cu（Ⅱ）配合物的合成及晶体结构

利用水热合成技术,成功合成了2种基于Keggin阴离子{XW12O40}4-（X=Si/Ge）的Cu（Ⅱ）配合物：H2[{Cu（4,4′-bipy）3/2（OH）（H2O）}2{XW12O40}].4H2O（X=Si,1;X=Ge,2）,通过单晶X-射线衍射分析、红外光谱、热重-差热分析及电化学手段对配合物进行了结构表征和基本的性质研究.单晶X-射线衍射分析表明,它们互为异质同构体,晶体结构可描述为Cu（Ⅱ）离子通过OH-基团和4,4′-bipy分子连接形成了一维Z形链,链与链之间进一步通过Keggin阴离子的两个端氧原子与Cu（Ⅱ）离子桥联,形成二维层状结构;沿b轴方向观察1和2的晶体结构,发现邻近的层与层之间距离为14.9.     

Effect of continuous annealing temperature on microstructure and properties of ferritic rolled interstitial-free steel

In this report, the microstructure, mechanical properties, and textures of warm rolled interstitial-free steel annealed at four different temperatures (730, 760, 790, and 820℃) were studied. The overall structural features of specimens were investigated by optical microscopy, and the textures were measured by X-ray diffraction (XRD). Nano-sized precipitates were then observed by a transmission electron microscope (TEM) on carbon extraction replicas. According to the results, with increased annealing temperatures, the ferrite grains grew; in addition, the sizes of Ti₄C₂S₂ and TiC precipitates also increased. Additionally, the sizes of TiN and TiS precipitates slightly changed. When the annealing temperature increased from 730 to 820℃, the yield strength (YS) and the ultimate tensile strength (UTS) showed a decreasing trend. Meanwhile, elongation and the strain harden exponent (n value) increased to 49.6% and 0.34, respectively. By comparing textures annealed at different temperatures, the intensity of {111} texture annealed at 820℃ was the largest, while the difference between the intensity of {111}<110> and {111}<112> was the smallest when the annealing temperature was 820℃. Therefore, the plastic strain ratio (r value) annealed at 820℃ was the highest.     

Synthesis of well-defined functional crystals by high temperature gas-phase reactions

Over the past decades, there have been many synthesis methods on producing well-defined crystals, due to their enormous application potentials in industrial field. Among them, high temperature gas-phase reactions （HTGR） approach may be one of the most promising processes for fabrication of well-defined crystals with controllable structure, size, shape, and composition. This review is focused on the recent progresses in synthesizing well-defined crystalline TiO2 dominated with, respectively, {001 } facets and { 105 } facets, one-dimensional ZnO and SnO2 nanorods/nanowires, MoS2 nanosheets as well as GaP, InP, and GaAs nanowires via HTGR approach. Although these research works were currently carried out on experimental scale, it is worth to note that the industrial importance of this HTGR approach for design and fabri- cation of well-defined crystals in the future owing to its advantages of continuous and scalable production with controlled dimensions and low cost.