X.X. Guo
,
J.S. Liu
金属学报(英文版)
The adaptive remeshing technique for quadrilateral elements consists of modules the
trigger of remeshing, the new mesh generation, adaptive refinement and interpolation
of field variables. The new adaptive mesh generation is the key problem. First, a
coarse mesh is created by using "loop algorithm". Subsequent local mesh adaptive
re¯nement is performed based on effective strain. Finally, a typical example of upsetting is given to test effcient of techniques, from which it is verified that the remeshing
algorithm developed here exhibits good performance and has high accuracy.
关键词:
adaptive remeshing
,
null
,
null
材料科学技术（英文）
The structure, specific heat, magnetic and electrical properties of MnTe(1-x)Sb(x) (x=0, 0.1, 0.15, 0.2 and 0.25) alloys have been investigated. The MnTe(1-x)Sb(x) alloys crystallize in a hexagonal NiAs-type structure, and the impurity of MnSb phase appears when x >= 0.15. The MnTe(0.9)Sb(0.1) compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K, showing that the magnetic properties of MnTe compound are very sensitive to little compositional change. The ferromagnetism in the MnTe(1-x)Sb(x) alloys with higher Sb contents may be attributed to the impurity of MnSb phase. Energy dispersive X-ray spectroscopy analysis on the MnTe(0.9)Sb(0.1) compound indicates that Sb is very difficult to dope into the lattice of MnTe. So the anomaly of resistivity at 300 K of MnTe(0.9)Sb(0.1) and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.
关键词:
Electronic transport property;Hysteresis loop;Specific heat;manganese telluride;semiconductors;ferromagnetism;scattering;exchange
Powder Diffraction
The structure transitions and phase relationships of DyFe(3-x)Al(x) compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x <= 0.45 crystallizes in the rhombohedral PuNi(3)-type structure with space group R (3) over barm and Z=9; for the 0.8 <= x<1.0 compounds, each has a hexagonal structure of the CeNi(3) type with space group P6(3)/mmc and Z=6; and each of the samples with 0.45<x<0.8 is a two-phase mixture of the PuNi(3)- and CeNi(3)-type structures. The calculated XRD intensities of the DyFe(3-x)Al(x) compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe(3-x)Al(x) compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45-0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe(2.33)Al(0.67) (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases. (C) 2010 International Centre for Diffraction Data. [DOI: 10.1154/1.3507088]
关键词:
X-ray powder diffraction;DyFe(3-x)Al(x) system;structure change;anomalous phase composition;magnetic-properties;intermetallic compounds;al substitution;rare-earth;fe;dy6fe23;refinement;aluminum;dy2fe17;co
Journal of Magnetism and Magnetic Materials
The ingot of Fe-(18-x) at% Ga-x at% Al (3 <= x <= 13.5) alloys was prepared from high purity elements using a high vacuum arc melting system. The X-ray diffraction patterns indicated that the alloys were disordered bcc A2 structure. The magnetostriction of the alloys was measured and the effect of partial substitution of Ga with Al on the magnetostriction of the alloys was investigated. Fe-9 at% Ga-9 at% Al alloy, the optimizing magnetostrictive alloy was found in Fe-(18-x) at% Ga-x at% Al (3 <= x <= 13.5) alloys. The saturated magnetostriction of the directional solidification Fe-9 at% Ga-9 at% Al rod is up to 135 ppm for 0 MPa and 221 ppm for 53 MPa. It was found that the alloy has the high linearity of the magnetostriction curve, the low hysteresis and saturated magnetic field, which suggests the directional solidification Fe-9 at% Ga-9 at% Al alloy is a potential candidate for magnetostrictive actuator and transducer applications. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Fe-Ga-Al alloy;Magnetostriction;Microstructure;fe-rich portion;phase-equilibria;system;elasticity;stability
Lizhi CHENG
,
Wei FENG
,
Xinquan DONG
,
Kuichang BAI and Kaiyuan HE (Dept. of Materials Science and Engineering
,
Northeastern University Shenyang 110006
,
China)
材料科学技术（英文）
The formation of nonequilibrium phase by mechanical alloying (MA) of Fe and B powders in a high energy vibration ball mill has been made for Fe100-xBx system with x=15. 30, 35, 45,55 and 70. By using the X-ray diffraction, magnetic measurement and M6ssbauer spectrummethods, it was revealed that the structure of the MA product varies with milling time and B contents.
关键词:
Physical Review B
NdCo(12-x)V(x) (2.2 <= x <= 2.6) crystallizes in the ThMn(12)-type structure and exhibits an unusual jump in the magnetization at a critical field B(C) that decreases with increasing V content. It was intriguing that the magnetization of the bulk samples below B(C) was very close to that of YCo(12-x)V(x) with the same V content. To investigate the nature of the magnetic order in these materials we have carried out powder neutron diffraction measurements as a function of temperature and magnetic field on the NdCo(9.5)V(2.5) composition. In zero field we find that both the Nd and Co ions have substantial ordered moments (similar to 2.9 and 0.4 mu(B), respectively) at low temperature (4 K), with the moments coupled ferromagnetically (T(C)=180 K) and aligned along the c axis. On a loose powder an applied field of 4 to 7 T rotates the particles so the c axis aligns with the field, indicating a strong uniaxial anisotropy that renders the system Ising-like. However, we find the same in-field magnetic structure and essentially the same values for the saturated magnetic moments as those in zero field. Magnetization data on magnetically prealigned samples reveal that for fields applied parallel to the (easy) c axis the magnetization saturates below 0.5 T at a magnitude that is in very good agreement with the moments determined from neutron diffraction. For fields applied perpendicular to the c axis, on the other hand, the magnetization data show a two-plateau behavior, explaining the original magnetization data on randomly oriented powders. The strong dependence of the magnetization on the direction of the applied magnetic fields indicates an occurrence of the first-order magnetization process due to the competing magnetocrystalline anisotropies of the Nd and the Co sublattices and of the higher-order terms of the anisotropy energy.
关键词:
rare-earth;intermetallic compounds;thmn12 structure;transition;anisotropy;crystal;fe;substitution;ndco9.5v2.5;compound
郭可信
金属学报
<正> X射线在金属学及金属物理这一学科中的应用日益广泛,它已经是从事金属研究的科学工作者所不可缺少的工具.同时,金属X射线学也已经成为一门新的边缘学科分支,是金属学及金属物理专业的必修课程.但是,在这方面,迄今为止尚无一本我国科学工作者编写的教材或参考书,仅有的几种译本亦都有内容贫乏与过时的缺点.因此,许顺生同志著的“金属X射线学”的出版是值得欢迎的.本书的内容范围相当广泛,并且是此较全面的.全书共26章,可以粗略地分五个部分:第一部分(1—5章):基本理论,包括X射线物理及晶体学基础,X射线衍射的几何及强度理论;第二部分(6—10章):各种实验方法,如劳厄、周转晶体、粉末及小角度散射法;第三部分(11—15章):X射线晶体学的一
关键词:
朱桂兰
,
何崇智
钢铁研究学报
简要介绍了德国布鲁克AXS公司新产品D8系列X射线衍射仪的特点、实验方法的分析软件及其应用.该系列仪器具有超前的技术,卓越的品质,可为物质微观结构的分析和前沿研究工作提供有效的解决方案.
关键词:
X射线衍射仪
Physical Review B
The temperature dependence of the elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) (x = 0.0, 0.1, and 0.2) random alloys are investigated by using the first-principles exact muffin-tin orbitals method. At 0 K, the calculated equilibrium parameters in both cubic L2(1) and nonmodulated tetragonal beta'''-Ni(2)MnGa are in good agreement with the available experimental data and other theoretical results. Separating the thermal effects into single electron excitation, volume expansion, phonon smearing, and magnetic terms, we find that phonon smearing gives the dominating positive tetragonal elastic constant (C') versus temperature (T) slope for the cubic phase. For Ni(2+x)Mn(1-x)Ga, the competition between the negative alloying effect (partial derivative C'/partial derivative x < 0) and the positive temperature effect (partial derivative C'/partial derivative T > 0) leads to nearly constant C'[x, T(M)(x)] at the martensitic transition temperature T(M)(x). For Ni(2)Mn(Ga(1-x)Al(x)), where both partial derivative C'/partial derivative x and partial derivative C'/partial derivative T are positive, however, due to the significantly decrease of T(M)(x), the critical C'[x, T(M)(x)] slightly decreases with Al doping. Furthermore, it is demonstrated that both the composition and the temperature dependence of C' are indispensable to get a reasonable theoretical T(M)(x).
关键词:
shape-memory alloys;ni-mn-ga;martensitic phase-transformation;potential model;heusler alloys;ni2mnga alloy;landau theory;approximation;transitions;disorder
Journal of Applied Physics
The crystal structure and superconducting properties of RuSr(2-x)Ba(x)GdCu(2)O(8) (0less than or equal toxless than or equal to0.1) have been investigated. X-ray powder diffraction (XRD) patterns show that the solid solution range is 0less than or equal toxless than or equal to0.1. The superconducting transition temperature was raised up to 35 K (zero) and 62 K (onset) for x=0.07, from 16 K (zero) and 45 K (onset) for x=0.0, and then T(C) decreases with x when x>0.07. Rietveld refinement for XRD data of RuSr(2-x)Ba(x)GdCu(2)O(8) show that the apical Cu-O(1) bond length increases with an increase of x, while the Ru-O(1) bond length decreases, This may account for the enhancement of the superconducting transition temperature. (C) 2004 American Institute of Physics.
关键词:
dc magnetization;rusr2gdcu2o8;ferromagnetism;coexistence;gd
