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STUDIES ON PRIMARY CRYSTALLIZATION OF RAPIDLY QUENCHED Al-Ni-Cu-Nd METALLIC GLASS BY USING HIGH RESOLUTION TRASMISSION ELECTRON MICROSCOPY

Y.D.Xiao , W.X.Li , D.Jacovkis , M.T.Clavaguera-Mora , J.Rodriguez-Viejo , N.Clavaguera

金属学报(英文版)

Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous rib-bon and the annealed samples were closely examined by means of differential scan-ning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in pri-mary crystallization into α-Al nanocrystalline particles, in order to understand struc-tural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of α-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at 110℃ for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃/min consist of large amount of α-Al fec crystal nanoparticles dispersed uni-formly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crustal is soft impinaement, instead of geometric impinqement.

关键词: rapid solidification , null , null

Spin waves in a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab)=J(cd)not equal J(bc)=J(da))

Physical Review B

The Hamiltonian for a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab) = J(cd) not equal J(bc) = J(da)) was established. An extended Bogoliubov transformation was developed by solving an equation group, consisting of 20 equations and 20 unknowns. The procedure for solving the equation group was carried out by introducing a simple way of reducing the numbers of the equations and the unknowns. The spin-wave spectra in the present system have been determined by performing the standard Holstein-Primakoff transformation and the Bogoliubov one. It has been found that the spin-wave spectra of the present system depend on the exchange constants and that the degeneracy of the spin-wave spectra remains. The results for a special case (J(ab) = J(bc)) i.e., an antiferromagnet are discussed briefly. The spin-wave spectra of the four-sublattice Heisenberg antiferromagnet are found to be degenerative also and they are linear in k for small k.

关键词: model

高分子专利j

高分子材料科学与工程

专利名称:具有改进的抗冲击性、尺寸稳定性和吹塑成形性能的热塑性ABS树脂组合物专利申请号:CN200580040787.3公开号:CN101065413申请日:2005.03.31公开日:2007.10.31申请人j韩国第一毛织株式会社根据本发明的热塑性ABS树脂组合物包括:(a)2

关键词: 专利名称 , 高分子 , 树脂组合物 , 专利申请号 , 尺寸稳定性 , 抗冲击性 , 株式会社 , 成形性能

Study on the Relationship Between J-Integral and COD

Y.G. Cao , X.Y. Sun

金属学报(英文版)

J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.

关键词: FRASTA , null , null

浅析CTOD和J积分的关系

周峰峦 , 郭震

物理测试 doi:10.13228/j.boyuan.issn1001-0777.20160084

推导了CTOD和J积分的关系,并且从试验角度利用三点弯曲试样进行CTOD试验,根据ASTM E1820对GB/T 21143-2014中公式34进行了评价,研究表明,在小屈服范围内,采用裂纹嘴张开位移可以同时得到CTOD和J积分,从而可以简化J积分的试验装置.

关键词: J积分 , CTOD , 小屈服

悬臂弯曲方法测定J_(Ic)和J_(Iscc)的探讨

null , null

金属学报

在工程上,经常由于应力腐蚀开裂和氢脆引起中强度钢结构件发生滞后破坏。这类脆断往往从结构件中预先存在的疲劳或焊接裂纹处开始,因此,运用传统的光滑试样的检验方法不能反映这类破坏的特点。 本文将弹塑性断裂力学中的J积分概念用于滞后破坏的研究,提出用带预制疲劳裂纹的悬臂弯曲试样测定J积分的临界值J_(Ic)和应力腐蚀开裂阈值J_(Iscc)的方法。测定了40CrNiMo钢的J_(Ic)值及其在硫化氢水溶液中的J_(Iscc)值。通过和三点弯曲方法测定的J_(Ic)值的对比,以及和满足线弹性条件时直接测定的应力强度因子K_I值的对比,说明这种方法的可靠性。最后,对悬臂弯曲方法的特点进行了讨论。

关键词:

J/Ψ衰变的Roper共振态结构的研究

平荣刚

原子核物理评论 doi:10.3969/j.issn.1007-4627.2004.02.026

通过J/Ψ→pp-,pN-*,N*N-*衰变,研究了Roper共振态的混杂态结构对衰变角分布和分支比的影响.计算结果表明,如果Roper共振态为纯混杂态,那么J/Ψ→pN-*,N*N-*的角分布几乎相等,而J/Ψ衰变到混杂态的衰变宽度还不到J/Ψ→pp-的1%,给出了Γ(J/Ψ→ N*p-)/Γ(J/Ψ→pp-)和Γ(J/Ψ→ N*N-*)/Γ(J/Ψ→pp-)随混合参数的变化关系,并讨论了在J/Ψ衰变中研究Roper混杂态结构的可能性.

关键词: Roper共振态结构 , 混杂态 , J

Magnetization, internal energy and specific heat in a three-sublattice ferrimagnet or ferromagnet with vertical bar J(ab)vertical bar=vertical bar J(bc)vertical bar not equal J(ca)

Journal of Physics-Condensed Matter

The temperature dependences of the magnetization, internal energy and specific heat in a three-sublattice ferrimagnet or ferromagnet with /J(ab)/ = /J(bc)/ not equal /J(ca)/ are calculated within the framework of the linear spin-wave approximation, by employing retarded Green's functions. For both the ferromagnet and the ferrimagnet, the internal energy and the specific heat decrease with increasing J ' /J and/or the value of the spins. For fixed values of S,, Sb, S, and J ' /J, the internal energy and the specific heat increase, whereas the sublattice magnetization decreases with increasing temperature theta. The three-sublattice ferrimagnet has some particular characteristics which are not shown by the systems with two sublattices. For ferrimagnets, the antiferromagnetism of the system becomes weaker with increasing J ' /J. The sublattice magnetization at low temperatures (also the magnetization M(0) at 0 K) of a ferrimagnet increases with increasing J ' /J for fixed values of S(a), S(b) and S(c). The effects of the spins S(a) (S,) and Sb On the magnetizations of other sublattices differ. The characteristics of the a-sublattice are the same as those of the c-sublattice, due to their similarity as well as the symmetry of the system. The behaviours of the b-sublattice are different from those of the a- and c-sublattices, due to the asymmetry of the three-sublattice system. The spin-value dependences of the spin deviation Deltam per spin land also the energy for the zero-point quantum fluctuation) of the system are different for different sublattices. These differences are ascribed to the asymmetry of the three-sublattice systems, which leads to the new intrinsic properties of the systems.

关键词: layered heisenberg ferrimagnets;spin-wave theory;elementary;excitations;superlattices;systems;magnetoresistance;antiferromagnet;interfaces

Spin waves in several Heisenberg systems: Three-sublattice with different exchange constants (J(ab)=J(bc)not equal J(ca)) and a superlattice with the elementary unit of four or three different layers

Physical Review B

The quadratic Holstein-Primakoff spin-wave Hamiltonian for three-sublattice Heisenberg systems with different exchange constants (J(ab)=J(bc)not equal J(ca)) was diagonalized by a three-step procedure. The classical ground state was examined and the effects of quantum fluctuation on the ground state were discussed. The 0 K spin reorientation angles due to quantum fluctuations were found to originate from the asymmetry of the system. As an extended application of the spin-wave study of the multisublattice systems, the spin-wave spectra of a Heisenberg superlattice, which has four or three magnetic atoms or spins, in each magnetic unit cell in the x direction, were solved analytically in terms of creation and annihilation operators. It has been found that the spin-wave spectra of the present superlattice systems depend on the exchange constants J and J(1), and that the degeneracy of the spin-wave spectra remains for the superlattice of four atomic layers and is partially removed for the superlattice of three atomic layers mainly due to the asymmetry of the system. Another type of splitting of the energy level occurs which differs for those levels with different degeneracies. The mixing of the interface and the bulk modes were found for the spin-wave dispersion of the superlattices. It was predicted that even for different superlattices having the same exchange constants (either J or J'), i.e., without the oscillation of the exchange coupling, the asymmetry can lead to the oscillation of magnetic properties, such as magnetization and giant magnetoresistance.

关键词: ferromagnetic superlattices;reorientation transitions;magnetic;superlattices;modes;temperatures;film

J55油井管质量的研究

贺道中 , 肖鸿光

钢铁研究 doi:10.3969/j.issn.1001-1447.2003.05.006

利用电子扫描电镜和能谱分析仪对J55油井管的缺陷进行分析,从冶炼工艺方面提出了控制J55油井管缺陷的措施.

关键词: J55油井管 , 缺陷 , 措施

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