Structural characterisation of reaction zone for friction stir welded aluminium-stainless steel joint

In the present investigation, commercially pure Al has been joined with 304 stainless steel (SS) by friction stir welding. The assembly finds widespread application in the field of cryogenics, nuclear, structural industries and domestic appliances. Microstructural characterisation was carried out using scanning and transmission electron microscopes. It has been found that diffusion of Fe, Cr and Ni is substantial within Al; however, diffusion of Al within 304SS is limited. Owing to interdiffusion of chemical species across the bondline, discrete islands of Fe3Al intermetallic form within the reaction zone. The rubbing action of tool over the butting edge of 304SS removed fine particles from 304SS, which were embedded in the stirring zone of Al matrix. Subsequently, austenite underwent phase transformation to ferrite due to large strain within this grain. Fracture path mainly moves through stirring zone of Al alloy under tensile loading; however, in some places, presence of Fe3Al compound has been also found.

Microstructural features of an iron-based laser coating

A high toughness wear resistant coating is produced by laser clad Fe-Cr-W-Ni-C alloys. The microstructural and compositional features of the laser-solidified microstructures and phase evolutions occurring during high temperature tempering at 963 K were investigated by using analytical electron microscopy with energy dispersive X-ray analysis. The clad coating possesses the hypereutectic microstructure consisted of M7C3 + (Y + M7C3) Du ring high temperature aging, the precipitation of M23C6 and M2C in austenite and in situ transformation of dendritic M7C3 to M23C6 and eutectic M7C3 to M6C occurred. The laser clad coating reveals an evident secondary hardening and superior impact wear resistance.

铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ATEM研究了铁基多元合金Fe-Cr-W-Ni-C激光熔覆层的微观组织、亚稳相结构特征以及高温时效时的亚稳相转变机制。结果表明组织为亚共晶组织，即γ+(γ+M_7C_3)，γ-奥氏体为具有较高合金度的过饱和亚稳相，M_7C_3(M为Cr,Fe,W)为六方结构的Cr基亚稳合金碳化物。熔覆组织在高温时效时存在两类碳化物形成机制，即亚稳γ中析出M_(23)C_6、M_2C与MC碳化物以及M_7C_3→M_(23)C_6与M_7C_3→M_6C的碳化物原位转变机制。熔覆组织具有较高的显微硬度并存在显著的二次硬化特征。

Measurements of thermal radiation in ultralight metal foams with open cells

Highly porous ultralightweight cellular metal foams with open cells have attractive mechanical, thermal, acoustic and other properties and are currently being exploited for high-temperature applications (e.g. acoustic liners for combustion chambers). In such circumstances, thermal radiation in the metal foam becomes a significant mechanism of heat transfer. This paper presents results from experimental measurements on radiative transfer in Fe-Cr-Al-Y (a steel-based high-temperature alloy) foams having high porosity (95 per cent) and different cell sizes, manufactured at low cost from the sintering route. The spectral transmittance and reflectance are measured at different infrared wavelengths ranging from 2.5 to 50 μm, which are subsequently used to determine the extinction coefficient and foam emissivity. The results show that the spectral quantities are strongly dependent on the wavelength, particularly in the short-wavelength regime (less than 25 μm). While the extinction coefficient decreases with increasing cell size, the effect of cell size on foam reflectance is not significant. When the temperature is increased, the total extinction coefficient increases but the total reflectance decreases. The effective radiative conductivity of the metal foam is obtained by using the guarded hot-plate apparatus. With the porosity fixed, the effective radiative conductivity increases with increasing cell size and increasing temperature. © IMechE 2004.

Nonequilibrium microstructures and phase evolutions of an iron-based laser clad coating

The microstructural and compositional features of the laser-solidified microstructures and phase evolutions occurring during high temperature tempering were investigated by using analytical electron microscopy with energy dispersive X-ray analysis. The cladded alloy, a powder mixture of Fe, Cr, W, Ni and C with a weight ratio of 10:5:1:1:1, was processed with a 3 kW continuous wave CO2 laser. The cladded coating possessed the hypoeutectic microstructure of the primary dendritic gamma-austenite and interdendritic eutectic consisting of (gamma+M7C3). The gamma-austenite is a nonequilibrium phase with extended solid solution of alloying elements. And, a great deal of fine structures, i.e., a high density of dislocations, twins, and stacking faults existed in austenite phase. During high temperature aging, the precipitation of M23C6, MC and M2C in austenite and in situ transformation of M7C3(+gamma) --> M23C6 and M7C3+gamma --> M6C occurred. The laser clad coating revealed an evident secondary hardening and superior impact wear resistance.

Rapidly solidified nonequilibrium microstructure and phase transformation of laser-synthesized iron-based alloy coating

The rapidly solidified microstructural and compositional features, the precipitation and transformation of carbides during tempering, and the impact wear resistance of an iron-based alloy coating prepared by laser cladding are investigated. The clad coating alloy, a powder mixture of Fe, Cr, W, Ni, and C with a weight ratio of 10:5:1.1.1, is processed using a continuous wave CO, laser. Microstructural studies demonstrate that the coating possesses the hypoeutectic microstructure comprising the primary dendritic gamma-austenite and interdendritic eutectic consisting of gamma-austenite and M7C3 carbides. gamma-Austenite is a non-equilibrium phase with an extended solid solution of alloying elements. During high temperature tempering at 963 K for 1 h, the precipitation of M23C6, MC and M2C carbides in austenite and in situ carbide transformation of M7C3 to M23C6 and M7C3 to M6C respectively are observed. In addition, the microstructure of the laser-clad coating reveals an evident secondary hardening and a superior impact wear resistance.

铁基激光熔覆合金设计及微观组织与性能研究

本文设计并制备了具有优良的强韧性能和高温性能的激光熔覆涂层。利用 SEM、TEMEY X－射线衍射仪等研究了涂层的化学成分、宏微观结构及其转变机制，同时研究了涂层强韧性及耐高温磨损性能及其影响机制。对激光溶覆涂层进行了合金化、微观组织、强韧化机制、加工工艺性能设计。合金系为 Fe-Cr-C-W-Ni，成分配比（质量分数），Fe:52-60%, Cr:24-30%, C:5-6%, W:4.5-7.5%, Ni:5-6%。强化机制为两相强化、亚结构强化及固溶强化，其中强化相为合金碳化物，基体相为合金元素过饱和度极高的韧性奥氏体。亚共晶及过共晶组织的领先凝固相分别为奥氏体及 M_7C_3 合金碳化物，两相共晶组织均为韧性相奥氏体和强化相 M_7C_3 合金碳化物。加工工艺控制领先凝固相的结构、组织演化及力学性能。熔覆组织在高温时效过程中形成大量新的碳化物。在过饱和奥氏体内部，可弥散析出细小的 Mc、M_2C 及 M_(23)C_6碳化物；在奥氏体与 M_7C_3 相界面，亚稳相M_7C_3发生原位转变，形成 M_(23)C_6 及 M_6C碳化物。激光熔覆合金具有较高的综合力学性能，熔覆涂层有高的显微硬度、优良的抗回火稳定性、显著的二次硬化特征、优异的抗磨粒磨损和冲击磨损性能。Fe-Cr-C-W-Ni 激光熔覆合金具有较低的裂纹形成倾向和良好的表面成形性能，这与奥氏体较高的高温韧塑性及合金的低熔点共晶特征密切相关；实验及理论分析表明，通过调整合金成分、激光工艺参数和后续热处理工艺，可获得具有不同强韧性能的熔覆涂层。

Metallaboratrane Facilitated E‒H Bond Activation and Hydrogenation Catalysis

The E‒H bond activation chemistry of tris-phosophino-iron and -cobalt metallaboratranes is discussed. The ferraboratrane complex (TPB)Fe(N₂) heterolytically activates H‒H and the C‒H bonds of formaldehyde and arylacetylenes across an Fe‒B bond. In particular, H‒H bond cleavage at (TPB)Fe(N₂) is reversible and affords the iron-hydride-borohydride complex (TPB)(μ‒H)Fe(L)(H) (L = H₂, N₂). (TPB)(μ‒H)Fe(L)(H) and (TPB)Fe(N₂) are competent olefin and arylacetylene hydrogenation catalysts. Stoichiometric studies indicate that the B‒H unit is capable of acting as a hydride shuttle in the hydrogenation of olefin and arylacetylene substrates. The heterolytic cleavage of H₂ by the (TPB)Fe system is distinct from the previously reported (TPB)Co(H₂) complex, where H₂ coordinates as a non-classical H₂ adduct based on X-ray, spectroscopic, and reactivity data. The non-classical H₂ ligand in (TPB)Co(H₂) is confirmed in this work by single crystal neutron diffraction, which unequivocally shows an intact H‒H bond of 0.83 Å in the solid state. The neutron structure also shows that the H₂ ligand is localized at two orientations on cobalt trans to the boron. This localization in the solid state contrasts with the results from ENDOR spectroscopy that show that the H₂ ligand freely rotates about the Co‒H₂ axis in frozen solution. Finally, the (TPB)Fe system, as well as related tris-phosphino-iron complexes that contain a different apical ligand unit (Si, PhB, C, and N) in place of the boron in (TPB)Fe, were studied for CO₂ hydrogenation chemistry. The (TPB)Fe system is not catalytically competent, while the silicon, borate, carbon variants, (SiP^R₃)Fe, (PhBP^iPr₃)Fe, and (CP^iPr₃)Fe, respectively, are catalysts for the hydrogenation of CO₂ to formate and methylformate. The hydricity of the CO₂ reactive species in the silatrane system (SiP^iPr₃)Fe(N₂)(H) has been experimentally estimated.

Quantificação e avaliação da biodisponibilidade de metais em sedimentos na Baía da Ribeira RJ

A toxicidade dos metais em ambientes aquáticos está relacionada à sua biodisponibilidade e esta, por sua vez, pode ser influenciada por diversos fatores. As características do sedimento fazem dele um importante compartimento para avaliação do nível de contaminação no ambiente aquático. A presente pesquisa teve por objetivo quantificar e avaliar a biodisponibilidade de metais em sedimentos da baía da Ribeira. Nessa região, encontram-se os bairros mais populosos de Angra dos Reis RJ. Essa baía está localizada na parte nordeste da baía da Ilha Grande, que consiste de um espaço pesqueiro, turístico e de importante valor econômico e industrial. Foram coletados 12 sedimentos na baía da Ribeira e determinados os teores dos metais Al, Cu, Cd , Cr, Fe, Mn, Ni, Pb e Zn, através da extração com água régia (protocolo BCR-701), e o potencial de toxicidade dos metais Cd, Cu, Ni, Pb e Zn pelo método de extração dos sulfetos voláteis em meio ácido e quantificação dos metais extraídos simultaneamente (em inglês Acid Volatile Sulfide and Simultaneously Extracted Metal, AVS/SEM). Também foram efetuadas medidas de pH, potencial redox (Eh), carbono orgânico, fósforo total e granulometria. Através desses dados, foi possível estudar correlações entre essas variáveis. As concentrações de cada metal são similares nas diferentes localizações dos sedimentos e não apresentam significativas diferenças com relação a estudos reportados para a área, com exceção do Pb que apresentou a mais alta concentração já reportada. Os valores de SEM/AVS (entre 0,02 e 0,2) menores que 1, indicam que há quantidade de sulfetos suficiente para o aprisionamento dos metais investigados. As correlações obtidas através da Análise dos Componentes Principais demonstram relação direta entre as concentrações da maioria dos metais extraídos por água-régia (Ni, Fe, Cr, Cu, Zn); entre os metais Mn, Pb, Al e o fósforo total; entre os teores de matéria orgânica, carbono orgânico total, fósforo total com as frações finas de silte e argila com o Eh. Os resultados sugerem que a região não sofre influência significativa de fontes antrópicas em relação a metais e que, segundo o AVS/SEM, esses se encontram pouco disponíveis para o ambiente e, portanto, apresentam baixo potencial tóxico

活性氧自由基与嘧啶碱基及其核苷反应的ESP研究

本文以MNP（2-methyl-2-nitrosopropane）为捕捉剂，利用自旋捕捉技术和ESR方法，室温条件下，研究了活性氧自由基与嘧啶碱基及其核苷在水溶液中的反应。确定了所产生的自由基类别，讨论了自由基的形成机制。在本工作中，我们在下列三种体系中，研究了活性氧自由基与嘧啶碱基及其核苷的反应。1.核黄素（B_2）水溶液中，O_2~-与嘧啶碱基及其核苷的反应。2.H_2O_2水溶液中，OH与嘧啶碱基及其核苷的反应。3.γ射线辐照水溶液过程中，OH与嘧啶碱基及其核苷的反应。在核黄素（B_2）水溶液中，通过U.V.光辐照，我们得到了活性氧自由基与尿嘧啶、胞嘧啶、胞苷、脱氧胞苷、胸腺嘧啶、胸腺核苷反应所产生的自由基，及由这些自由基与MNP自旋加合物的ESR谱。确认了自由基Ⅰ，Ⅱ，Ⅲ，Ⅳ，Ⅴ，Ⅵ的存在。为了判别与嘧啶碱基或嘧啶核苷反应的活性氧自由基的种类，我们在下列三种条件下进行了测试：（1）加入适量DETAPAC（2）通N_2或Ar除O_2；（3）加入H_2O_2酶，均未得到ESR信号。据此，我们排除了O_2~-与嘧啶碱基或嘧啶核革直接反应的可能性。确认与嘧啶碱基或嘧啶核苷发生直接反应的是OH，其形成是Fenton反应的结果。 Fe~(2+) ＋ O_2~- → H_2O_2 ＋ Fe~(3+) （a） Fe~(2+) ＋ H_2O_2 → ·OH ＋ OH~- ＋ Fe~(3+) （b）Fe~(3+) ＋ O_2~- → Fe~(2+)＋O_2 （c）通过Fenton反应，O_2~-转化成·OH，间接与嘧啶或核苷发生了反应。U.V.光照含有MNP和1％H_2O_2的样品水溶液，我们确定了·OH与嘧啶碱基及其核苷反应所产生的自由基Ⅰ，Ⅱ，Ⅲ，Ⅳ，Ⅴ，Ⅵ，Ⅶ，Ⅷ，Ⅸ，Ⅹ。发现，·OH与尿嘧啶及其核苷，胞嘧啶及其核苷的反应，主要有二种形式：其一，·OH加合到嘧啶环的C_5－C_6双键上，形成C_5位或C_6位自由基；其二，·OH夺取C_5位上的H，开成C_5'位自由基。·OH不与胸腺核苷的糖单元发生反应，仅与其嘧啶环反应，形成Nu位和C_5位自基。γ射线辐照过程中，·OH与嘧啶碱基及其核苷的反应与H_2O_2体系中的情况类似。辐照剂量则对反应的影响较大，低于1.0 * 10~4 rad，不发生反应；1.0 * 10~6 rad，则发生交联反应，只有1.0 * 10~5 rad的辐照剂量比较适宜。

玫瑰花芽分化期矿质元素和内源激素的变化规律

本文以沈阳市于洪区玫瑰种植示范区内多季花冷香玫瑰和单季花平阴玫瑰为研究对象，通过野外采样并测定了两者在花芽分化期矿质元素（P、K、Ca、Mg、Fe、Zn、B、Mn、Cu）和内源激素（IAA、GA、ZR、ABA）的含量，并对其含量及比值变化进行分析，初步确定了玫瑰花芽分化与元素、激素之间的相互关系。研究结果将为玫瑰花期的化学调控、提高产花量和正确制定栽培技术措施提供理论依据，也为玫瑰进一步开发利用打下基础。主要结论：1．在冷香玫瑰和平阴玫瑰的整个花芽分化期，P、K、Cu、Zn大体上均呈下降趋势，表明它们可能参与玫瑰成花；ca、Mg在冷香玫瑰和平阴玫瑰的花蕾形成期含量都下降，可能意味着ca、Mg参与两者的花蕾形成；Fe与玫瑰花芽分化关系不大；高含量的B和Mn有利于两者花蕾形成。2．在冷香玫瑰和平阴玫瑰花蕾形成期，IAA和GA出现低水平，ZR和ABA出现高水平，激素比值（ABA/GA，ABA／IAA，ZR/GA，ZR/IAA）出现高水平，表明ABA和ZR促进两者开花；而IAA和GA抑制两者开花；高比例的（ABA/GA，ABA/IAA，ZR/GA，ZR/IAA）有利于两者开花。

树木年轮元素分析

本文通过长白山阔叶红松林主要树种——红松（Pinus koraiensis）、蒙古栎（Quercus mongolica）木质部年轮中Pb、Cd、As、Zn、Cu、Mn、Al、Fe、Cr、Ti、V、Ni、P、K、Ca、Mg、Na等元素的含量分析，试图追溯和再现长白山地区生态环境的历史变迁。研究结果表明：红松、蒙古栎树木年轮中Pb、Cu、Fe、Cr、Ti、V、Ni、As等微量元素的浓度都呈现一致的时间动态形式。除木髓附近年轮中略高以外，而后近二百年时期的年轮内，元素深度保持比较一致的低水平。从而证明近代长白山生态环境一直相对稳定，目前人类环境冲击对该地区森林生态系统的影响尚不明显。红松、蒙古栎树皮和木质部年轮中有毒有害元素的含量可作为同一气候带类似树种的生物背景值。在相对原始、洁净的地区进行树木年轮元素分析，使年轮中元素的自然行为特点得以清晰展现。如边心材转化对Mn、Mg、Ca等元素再分布的影响，木质部元素含量的排列顺序，年轮中元素之间的相互联系等。与此同时，本文亦对年轮法有效性和准确性地影响因子，如木材类型、元素的再迁移、树木生长形式作了初步探讨，为我国今后开展该领域的研究提供了重要的科学依据。

非晶态合金的表面辐照效应研究

本工作用120Kev的He~+离子对非晶态Ni_(60)Nb_(40)、Fe_(40)Ni_(38)Mo_4B_(18)、Fe-Ni-B合金样品进行了辐照，辐照剂量为1.6、2.0、2.5，3.0 * 10~(18)/cm~2四种。借助X射线衍射扫描电子显微镜（SEM），内转换电子穆斯堡文谱（CEMS）等方法对辐照前后的样品进行了分析。X射线衍射结果表明在冷却靶的辐照条件下，样品辐照前后的非晶状态来改变，但辐照产生了原子的重排。SEM研究发现：表面发论的形成须一定的临界剂量对于Ni_(60)N_(240)，所需临界剂量最高；随剂量的增加，在所研究的剂量范围内，发论大小增大且来观察到表面发论的破裂与剥学；对不同组织的非晶合金，其发论程度稍有不同；辗压减药不影响材料的发论性质；表面结构的粗糙有助于降低发论程度；晶化样品，发论程度的显加剂。CEMS分析指出；辐照使结构的天度增加，有效的平均原子间距减小；因辐照导致原子的重新溶合使CSRO降低；随辐照首先的缺陷周围自旋取向及急进的应力源的变化。磁各向异性发生了变化

营养元素调控下南瓜组培根化感作用的初步研究

通过调节B5培养基中的组分,研究了金钩南瓜组培根在五种营养元素(P、Mg、Fe、Cu、B)四个浓度梯度(1/2 B5、B5、3/2 B52、B5)培养下化感作用的响应模式以及对黑籽和金钩南瓜两种受体幼苗生长的影响。结果表明:不同营养元素对受体植物幼苗生长的影响不一致,与元素含量显著相关,而且依赖于受体选择。五种营养元素在亏缺(1/2 B5)和正常(B5)条件下南瓜组培根过滤液对受体植物幼苗生长均表现为抑制作用;而适量增加营养元素的条件下(3/2 B5和2 B5),一般表现为促进作用,但2 B5含量下,B元素导致金钩南瓜的自毒作用,而Fe能引发金钩南瓜组培根过滤液对黑籽南瓜的抑制作用。因此理论上初步得出P和Mg元素可以降低南瓜根系的毒害作用,而Fe、Cu和B元素对南瓜根系的化感调控作用与品种选择有关,这对调控施肥、降低设施农业中葫芦科作物的连作障碍具有一定的参考意义。

平阴玫瑰花芽分化期叶片矿质元素含量动态变化

分析了平阴玫瑰叶片中P,K,Ca,Mg,Fe,Cu,Zn,Mn,B共9种矿质营养元素在花芽分化的7个生长时期含量动态变化及其相关性。结果表明,在平阴玫瑰花芽分化期间P,K,Zn,Cu大体上呈下降趋势;Ca除现蕾前含量陡然下降外,随叶片成熟含量呈现上升趋势;Mg,Fe,Mn,B含量波动频繁且变化各异。P与K,Zn,Cu均达到极显著正相关;K与Fe,Zn,Cu也达到极显著正相关;Fe与Mn,Zn与Cu之间均达到极显著正相关。平阴玫瑰叶片中9种矿质营养元素含量按高低排序为:Ca>K>P>Mg>Fe>Mn>B>Zn>Cu。