材料期刊网

SOLIDIFICATION CHARACTERISTICS OF HIGHLY UNDERCOOLED Ag-Ge EUTECTIC ALLOYS

C.X.Dong , X.Y.Luand B.B.Wei(Laboratory of Materials Sciencein Space , Northwestern Polytechnical University , Xi'an 710072 , China)

金属学报(英文版)

The Ag-Ge eutectic alloy system was intensively investigated with respect to its solidification characteristics at large undercoolings which were obtained by the B2O3 glass fluxing technique combined with argon protection. Grain size refinement was found in the Ag-15 wt% Ge hypoeuteciic alloy. With inereasing undercoolings the feather-like structure disappeared in the Ag-19wt% Ge eutectic alloy, and even silver slips showed up at sufficient undercoolings. Nevertheless, the fact that germanium had nucleated in preference to silver was indicated by a fine germanium line in the middle of the silver slips. The various morphologies of the germanium phase in the Ag-25 wt% Gehypereutectic alloy including the five-fold symmetry structure were explained by the joint action of high undercoolings (i.e. growth velocities) and density differences. The corpled zone of this alloy system was qualitatively estimated.

关键词: Ag-Ge alloys , null , null , null

Study of properties of mixed ferro-ferrimagnetic ising compounds with (A(x)B(1-x))(y)C

Communications in Theoretical Physics

The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(x)B(1-x))(y)C-z where A(z) B-z and C are three different magnetic ions and form three different sublattices, are studied by using the standard mean-field theory. The phase diagram which is related to experimental work of molecule-based ferro-ferrimagnet ((NixMn1-xII)-Mn-II)(1.5)[Cr-III(CN)(6)].zH(2)O is obtained. The magnetization curves(z) internal energy(z) and specific heat of the same mixed (A(x)B(1-x))(y)C system are also investigated.

关键词: mixed ferro-ferrimagnet;Ising model;phase diagram;internal energy;specific heat;mean-field analysis;magnetic-properties;prussian blue;alloy

X射线CT技术在C/C复合材料研究中的应用

李新涛 , 张东生 , 冯志海 , 赵高文

宇航材料工艺 doi:10.3969/j.issn.1007-2330.2016.01.007

分析了X射线CT技术的基本原理和成像模式,综述了X射线CT技术在C/C复合材料的密度测量、孔隙率、孔隙形状和分布等量化表征中的应用.同时介绍了X射线CT图像在C/C复合材料力学性能预测和裂纹扩展规律研究中的应用.

关键词: C/C复合材料 , CT技术 , 微观结构 , 力学性能 , 裂纹扩展

Structure, phase transformation, and magnetic properties of R(16)Fe(76-x)Co(x)C(8) (R equivalent to Nd, Dy; 0 <= x <= 76) alloys prepared by a remilling process

Journal of Applied Physics

The effect of Co substitution on structure, phase transformation, and magnetic properties of R(16)Fe(76-x)Co(x)C(8) (R equivalent to Nd, Dy; 0 <= x <= 76) alloys prepared by a remilling process has been studied systematically. The process of remilling and subsequent annealing is more beneficial for the formation of Nd(2)(Fe,Co)(14)C compound in Nd(16)Fe(76-x)Co(x)C(8) alloys than in Dy(16)Fe(76-x)Co(x)C(8) alloys. The R(2)(Fe,Co)(14)C phase is obtained for Nd(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 20 and Dy(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 25. Higher Co content results in the formation of Nd(2)(Fe,Co)(17)C(delta)-type phase and Dy(Fe,Co)(7) phase for Nd(16)Fe(76-x)Co(x)C(8) and Dy(16)Fe(76-x)Co(x)C(8) alloys, respectively. The high coercivity, (i)H(c)=48.5 kOe, is achieved for Dy(16)Fe(51)Co(25)C(8) alloy. (C) 2008 American Institute of Physics.

关键词: permanent-magnets;r2fe14c;carbides;carbon

{112}&#x0003C;111&#x0003E;孪生的形核和长大及终止的&#x003c9;点阵机制^&#x0002A;

吴松全 , 杨义 , 李阁平 , 平德海 , 胡青苗 , 杨锐

金属学报 doi:10.11900/0412.1961.2015.00309

针对体心立方(bcc)结构金属及合金{112}&#x0003C;111&#x0003E;孪生的&#x003c9;点阵机制, 利用点阵模型详解了bcc结构金属及合金{112}&#x0003C;111&#x0003E;孪晶形核、长大和终止全过程. 模型揭示了孪晶可以通过&#x003c9;&#x02192;bcc转变过程形成孪晶核胚, 再通过孪晶核胚生长或合并的方式长大, 最终与特殊位向&#x003c9;相作用受阻而停止. 该机制说明了{112}&#x0003C;111&#x0003E;类型孪晶是一种相变孪晶.

关键词: 金属和合金 , 孪晶 , 相变 , &#x003c9;点阵

Composition-Dependent Structural and Electronic Properties of alpha-(Si(1-x)C(x))(3)N(4)

Journal of Physical Chemistry C

The highly unusual structural and electronic properties of the alpha-phase of (Si(1-x)C(x))(3)N(4) are determined by density functional theory (DFT) calculations using the Generalized Gradient Approximation (GGA). The electronic properties of alpha-(Si(1-x)C(x))(3)N(4) are found to be very close to those of alpha-C(3)N(4). The bandgap of alpha-(Si(1-x)C(x))(3)N(4) significantly decreases as C atoms are substituted by Si atoms (in 2 most cases, smaller than that of either alpha-Si(3)N(4) or alpha-C(3)N(4)) and attains a minimum when the ratio of C to Si is close to 2. On the other hand, the bulk modulus of alpha-(Si(1-x)C(x))(3)N(4) is found to be closer to that of alpha-Si(3)N(4) than of alpha-C(3)N(4). Plasma-assisted synthesis experiments of CN(x) and SiCN films are performed to verify the accuracy of the DFT calculations. TEM measurements confirm the calculated lattice constants, and FT-IR/XPS analysis confirms the formation and lengths of C-N and Si-N bonds. The results of DFT calculations are also in a remarkable agreement with the experiments of other authors.

关键词: chemical-vapor-deposition;silicon-carbon nitride;thin-films;optical-properties;room-temperature;alpha-phase;growth;hard;photoluminescence;microstructure

Fe-X-C系马氏体相变热力学

徐祖耀

金属学报

Fe-X-C系马氏体相变时的△G_(Fe-X-C)~(γ→α)为:△G_(Fe-X-C)~(γ→α)=_(xFe)△G_Fe~(γ→α)+_(XC)RT×ln_(γ_C~α/γ_C~γ)+x_i△G_i~(γ→α)+△Ω~(γ→α)其中γ_C~α和γ_C~γ分别表示碳在Fe-X-C系铁素体和奥氏体内的活度系数.对Fe-Ni-C和Fe-Cr-C系所求得的M_S值和实验值很好符合.碳在Fe-X-C系的活度值及对奥氏体的强化作用主要决定Fe-X-C系的M_s值.碳是决定Fe-X-C系相变驱动力的主要元素.

关键词:

Ti-X-C(X=Si,Al)三元体系的元素机械合金化

张志力 , 周洋 , 艾明星

稀有金属材料与工程

采用Ti,Si,Al粉和石墨粉等元素作为主要原料,利用行星式球磨机,研究通过机械合金化法(MA)的反应球磨技术(RBM)活化烧结制备Ti3SiC2和Ti3A1C2粉末材料.通过X-射线衍射、扫描电镜等手段,分析研究了机械合金化过程中的元素组织结构变化和可能的机械化学反应.提出实验中机械合金化趋向于界面原子逐渐扩散的反应机制.

关键词: 机械合金化 , 三元碳化物 , 反应球磨

Ti-X-C(X=Si,Al)三元体系的元素机械合金化

张志力 , 周洋 , 艾明星

稀有金属材料与工程

采用Ti,Si,Al粉和石墨粉等元素作为主要原料,利用行星式球磨机,研究通过机械合金化法(MA)的反应球磨技术(RBM)活化烧结制备Ti3SiC2和Ti3A1C2粉末材料.通过X-射线衍射、扫描电镜等手段,分析研究了机械合金化过程中的元素组织结构变化和可能的机械化学反应.提出实验中机械合金化趋向于界面原子逐渐扩散的反应机制.

关键词: 机械合金化 , 三元碳化物 , 反应球磨

MAGNETIC PROPERTIES OF Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)ALLOYS

XING Feng JIANG Chao HE Wenwang Department of Physics , Peking University , Beijing , China [Originally published in ACTA METALL SIN (CHINESEEDN) 24 (5) 1988pp B348—B352 , received 22 October 1986:in revised form 8 May 1987]

金属学报(英文版)

The magnetic properties of Nd_2(Fe_(1-x)M_x)_(14)B(M=C and Si) compounds have been investi- gated.Substituting Fe by small amount of metalloid C and Si atoms,the compounds are in tetragonal structure and have uniaxial anisotropy.The substitution of C for part of Fe de- creases the Curie temperature of the compounds and the intrinsic coercivity of bond samples at low temperature.The replacement of Fe by Si makes the Curie temperature increase with a maximum at the vicinity of x=0.15.When the range of the content of Si is 0≤x≤0.10,the coercivity distinctly increases at room temperature.from 62.7 kA/m at x=0 to 138.7kA/m at x=0.06,where the residual magnetization has a maximum:in the mean time the saturation magnetization decreases only by a small amount.

关键词: Nd-Fe-B alloy , null , null