Shanthi Subramanian
,
David Muller
,
John Silcox and Stephen L.Sass (Department of Materials Science and Engineering and Department of Applied and Engineering Physics
,
Cornell University
,
Ithaca. NY 14853)
金属学报(英文版)
Local chemistry plays an important role in determining the cohesive strength of grain boundaries in Ni3Al. Doping with B increases the room temperature ductility and changes the fracture mode from intergranular to transgranular, while doping with Zr increases the ductility but leaves the fracture mode predominantly intergranular.Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive X-ray Spectroscopy (EDS) were used to probe the changes in local bonding (and hence the cohesive strength) produced by changes in local chemistry at large angle boundaries in Ni3Al.In addition , small angle tilt boundaries were studied to correlate structure with Nienrichment at the interface. B segregation to Ni-rich grain boundaries was shown to make the bonding similar to that of the bulk, thereby increasing their fracture resistance. Ni-enrichment does not occur in the presence of Zr segregation to grain boundaries. Ni-enrichment to antiphase boundaries (APB) in small angle tilt boundaries lowers the APB energy by reducing the number of high energy Al-Al interactions across the interface. Ni-enrichment to large angle boundaries is expected to produce a similar effect on energy.
关键词:
: grain boundary chemistry
,
null
,
null
,
null
王夫成
,
詹马骥
,
郎经纬
,
王若民
,
陈国宏
,
杜晓东
表面技术
doi:10.16490/j.cnki.issn.1001-3660.2015.09.019
目的：研究老旧高压输电耐张线夹内部交流腐蚀。方法截取已运行35 a的耐张线夹并解剖,采用扫描电子显微镜分析腐蚀区的微观形貌,采用X 射线衍射仪、能谱仪和X射线光电子能谱仪对腐蚀区元素及物相进行分析鉴定,分析线夹内部腐蚀损伤演化过程。结果线夹内表面与铝线表面局部出现大量白色腐蚀产物和黑色覆盖物,白色腐蚀物呈粉末和片层两种形态。分析表明,腐蚀产物相组成为Al2 O3,AlO( OH)和AlOOH；黑色覆盖物随深度增加而减少,黑色区域主要元素为Al,O和C,物相组成为Al2 O3,C( graphite)和含C有机物。钢芯锌层破坏区的内层铝线更易腐蚀,腐蚀区呈灰黑色,微观形貌为富铁元素颗粒镶嵌在其它腐蚀产物中,区域的主要元素为Al,C,O,Fe和Zn,Fe元素存在形式为Fe2 O3；钢芯表面镀锌层局部腐蚀严重,呈现平面型点蚀形貌,主要元素为Zn,Al,C和O,Zn腐蚀产物为六边纤锌矿结构ZnO。结论内部交流腐蚀原因为液体渗入,同时腐蚀产生大量的热致使材料分解。
关键词:
耐张线夹
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交流腐蚀
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点蚀
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微观形貌
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腐蚀产物
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热分解
N.H.March
材料科学技术（英文）
A condition for local moment formation in metals derived by Stoddart and March (Ann. Phys. NY 1972 64, 174) is first used to discuss the ferromagnetism of body-centred-cubic Fe. A less detailed discussion is also added on Ni and Co. This leads into a treatment of the nonlinear response of such 3d ferromagnets to dilute substitutional impurities. Antiferromagnets responding to local changes in the exchange field caused by such impurities are also studied, Mn in Cr being one such system discussed. The paper concludes with a brief summary of clusters of transition metal atoms, with most attention devoted to Cr and to Mn.
关键词:
Journal of Applied Physics
The structure and magnetic properties of Nd2Fe14BNdelta-based alloys prepared by mechanical alloying have been investigated. For the Nd14Fe78B8Ny series, a large amount of NdN, alpha-Fe, and a small Nd2Fe14B phase are observed in x-ray diffraction patterns. With increasing Nd content, the amount of the Nd2Fe14BNdelta phase increases and alpha-Fe decreases gradually. When x greater than or equal to 25 in the NdxFe92-xB8Ny systems, some amount of the N-containing, Nd-rich phase appears. Meanwhile, the content of the nitrogen in the Nd2Fe14BNdelta phase decreases and, correspondingly, the Curie temperature decreases. The coercivity and the maximum magnetic energy product of this series attain maxima at x=25. A coercivity as high as 20 kOe has been achieved. The effect of nitrogen on the formation, composition, and magnetic properties of the Nd2Fe14BNdelta compound is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)22208-1].
关键词:
phase;sm
Xinguo ZHAO
,
Zhidong ZHANG
,
Zhijun GUO
,
Wei LIU
,
Dianyu GENG
,
Baozhi CUI
材料科学技术（英文）
The alloy with nominal composition Sm-2(Fe0.94Ti0.06)(l7) is prepared by are-melting, hydrogenation and nitrogenation processes. The Sm-2(Fe0.94Ti0.06)(17) alloy has a single phase of Sm-3(Fe, Ti)(29) with the Nd-3(Fe, Ti)(29)-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300 degrees C. The hydrogenation at 800 degrees C mainly shows a HDDR process. The HD and nitrogenation at 500 degrees C result in increasing the Curie temperature of the alloy by 72 degrees C and by 158 degrees C due to lattice expansions, respectively. The anisotropic and isotropic Sm-3(Fe, Ti)(29)Ny magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm-3(Fe, Ti)(29)Ny powders achieved in the above two processes are: (i) B-r=0.82 T, H-i(c)=4.48 kA/cm, (BH)(max)=54.3 kJ/m(3), (ii) B-r=0.68 T, H-i(c)=8.14 kA/cm, (BH)(max)=66.4 kJ/m(3).
关键词:
Journal of Magnetism and Magnetic Materials
Sm1-xFe7+x (0 less than or equal to x less than or equal to 0.9) alloys were induction-melted and rapidly quenched at various wheel velocities of 20-50 m/s. The results of X-ray diffraction show that for the composition of 0 less than or equal to x less than or equal to 0.1 the rhombohedral Th2Zn17-type structure is the main phase, and for the composition of 0.2 less than or equal to x less than or equal to 0.9 the hexagonal TbCu7-type structure is formed. AC initial susceptibility experiments indicate that at annealing temperatures below 580 degrees C the amorphous phase is crystallized to the TbCu7-type phase, while annealing up to 800 degrees C the TbCu7-type phase is transformed to the Th2Zn17 phase. After nitrogenation, the optimal condition for the best magnetic properties is obtained in Sm12.5Fe87.5Ny, quenched at 50 m/s and annealed at 700 degrees C for 30 min, and consequently nitrogenated at 460 degrees C for 4 h. The best result for the coercivity H-i(c) of the Sm12.5Fe87.5Ny achieved is 18.9 kA/cm (23.7 kOe).
关键词:
quenching;Sm1-xFe7+x (O<=x<=0.9) alloys;Th2Zn17-type structure;TbCu7-type structure;nitrogenation;earth intermetallic compounds;sm-fe-n
材料科学技术（英文）
The alloy with nominal composition Sm-2(Fe0.94Ti0.06)(l7) is prepared by are-melting, hydrogenation and nitrogenation processes. The Sm-2(Fe0.94Ti0.06)(17) alloy has a single phase of Sm-3(Fe, Ti)(29) with the Nd-3(Fe, Ti)(29)-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300 degrees C. The hydrogenation at 800 degrees C mainly shows a HDDR process. The HD and nitrogenation at 500 degrees C result in increasing the Curie temperature of the alloy by 72 degrees C and by 158 degrees C due to lattice expansions, respectively. The anisotropic and isotropic Sm-3(Fe, Ti)(29)Ny magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm-3(Fe, Ti)(29)Ny powders achieved in the above two processes are: (i) B-r=0.82 T, H-i(c)=4.48 kA/cm, (BH)(max)=54.3 kJ/m(3); (ii) B-r=0.68 T, H-i(c)=8.14 kA/cm, (BH)(max)=66.4 kJ/m(3).
关键词:
sm
杨月英
,
林峰
,
王建江
,
刘宏伟
,
付永信
稀有金属材料与工程
采用幂函数分布形式设计梯度过渡涂层,以Ti-B4C-C团聚粉和Ni-Al自粘结复合粉的混合物为自蔓延反应火焰喷涂体系,在45号钢基体表面制备了Ti(Cx,Ny)-TiB2和NimAln梯度过渡的复相陶瓷涂层,研究了梯度过渡涂层的组织特点与耐磨性能.研究表明,当梯度指数为1,涂层按6层设计时,涂层为典型的多相非均质结构.Ti(Cx,Ny)-TiB2复相陶瓷与NimAln金属间化合物实现了沿涂层厚度方向的梯度过渡连接.梯度过渡陶瓷涂层的耐磨性是普通45号钢耐磨性的14倍,涂层磨损失效过程受粘着磨损与磨粒磨损共同作用,失效过程中陶瓷相的剥落是涂层磨损的关键环节,涂层中的粘接相、氧化物相和孔隙对涂层磨损有重要影响.
关键词:
SHS反应火焰喷涂
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梯度涂层
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组织
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耐磨性能
