Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
C.Y. Choi D.C. Kim D.G. Nam Y.D. Kim Y.D. Park
材料科学技术（英文）
Currently, in the automotive industry, joining of the aluminum alloys with the steel is a crucial problem to be solved. Conventional joining techniques including resistance spot and gas metal arc welding are not acceptable for those applications due to a number of metallurgical problems. The investigation was carried out to develop the hybrid joining process combining the resistance spot welding and brazing. In this study, an attempt was made to apply hybrid process to the joining of dissimilar sheet metals, Al-Mg-Si (6000 series) alloy and low carbon steel sheet. Hybrid process (resistance spot weld/brazing) using filler metal was found to be effective to overcome the incompatibility between aluminum alloy and steel. Although hybrid joining process of Al alloy sheet and steel sheet did not produce acceptable bond strength, it was proved to have reasonable interfacial
bond layer if the optimal process condition was applied.
关键词:
Hybrid joining
,
Aluminum
,
Steel
,
Welding
C.Y. Choi D.C. Kim D.G. Nam Y.D. Kim Y.D. Park
材料科学技术（英文）
Currently, in the automotive industry, joining of the aluminum alloys with the steel is a crucial problem to be solved. Conventional joining techniques including resistance spot and gas metal arc welding are not acceptable for those applications due to a number of metallurgical problems. The investigation was carried out to develop the hybrid joining process combining the resistance spot welding and brazing. In this study, an attempt was made to apply hybrid process to the joining of dissimilar sheet metals, Al-Mg-Si (6000 series) alloy and low carbon steel sheet. Hybrid process (resistance spot weld/brazing) using filler metal was found to be effective to overcome the incompatibility between aluminum alloy and steel. Although hybrid joining process of Al alloy sheet and steel sheet did not produce acceptable bond strength, it was proved to have reasonable interfacial
bond layer if the optimal process condition was applied.
关键词:
Hybrid joining
,
Aluminum
,
Steel
,
Welding
D.Han
,
S.R.Qiao
,
M.Li
,
J.T.Hou
,
X.J.Wu
金属学报(英文版)
The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.
关键词:
2D-C/SiC
,
null
,
null
Hejun Li
材料科学技术（英文）
2D needle-punched fiber felt was infiltrated by a kind of rapid isothermal chemical vapor infiltration technique.
The infiltration process and texture transition of the infiltrated C/C composites were investigated. The porosity
and the variations of the cumulative pore volume were determined by mercury porosimetry. The texture of
matrix carbon was studied under a polarized light microscope. The results show that the relative mass gain
of the sample increases directly as the infiltration time at the initial stage until 20 h, and subsequently the
increasing rate of the relative mass gain decreases gradually with the prolonging of infiltration time. Three layers
of pyrocarbon were formed around fibers. Low-textured pyrocarbon was obtained at the initial stage. With the
densification going on, high-textured pyrocarbon was formed on the surface of low-textured pyrocarbon. Then,
low-textured pyrocarbon was produced again during the final stage of densification. The texture transition is
ascribed to the variation of the ratio of cumulative inner surface area to volume of pores and the gas partial
pressure in pores.
关键词:
C/C composites
,
Isothermal chemical vapor infiltration (ICVI)
,
Pyrocarbon
,
Mercury porosimetry
,
Polarized light microscope
周颖
,
黄志尧
,
王保良
,
冀海峰
,
李海青
工程热物理学报
本文探讨了将电容耦合式非接触电导测量(Capacitively Coupled Contactless Conductivity Detection,C4D)技术应用于毫米级管径气液两相流气泡速度测量的可行性,提出了一种结合C4D技术及互相关测速原理的气泡速度测量新方法.研究包括两个部分:首先,结合串联谐振原理,研制了一种适用于气泡速度测量的新型三电极C4D传感器;其次,利用所研制传感器获得的两组电导信号,根据互相关测速原理实现气泡的速度测量.作为初步研究,在内径6.0 mm的竖直管内进行了气泡速度测量实验.实验结果表明将C4D技术运用于毫米级管径气液两相流气泡速度测量是可行的,所提出的气泡速度测量方法是有效的.
关键词:
电容耦合式非接触电导测量
,
毫米级管道
,
气泡
,
速度测量
,
互相关测速
吴小军
,
乔生儒
,
程文
,
邹武
,
崔红
,
王坤杰
新型炭材料
以X-Y平面依次铺设炭纤维束、Z向穿插炭棒的4D软硬混编为预制体,采用沥青液相常压、高压浸渍/炭化-石墨化循环致密工艺制备4D-C/C复合材料.通过该材料Z向(炭棒方向)的拉伸实验,测定其拉伸性能和力学行为,并采用SEM分析试样表面及断口形貌.结果表明:宏观上拉伸试样以炭棒整体拔出的形式破坏;细观尺度上,试样表面形成了与载荷方向垂直的贯穿性裂纹,裂纹以2mm左右的距离呈等间距分布;材料进一步的破坏过程中,基体裂纹在X-Y向纤维束中呈线性扩展,快速分割了基体材料,使4D-C/C复合材料的拉伸破坏演变为1D-C/C复合材料的破坏模式,由于炭棒与基体炭界面结合弱,炭棒以拔出方式失效和破坏.
关键词:
软硬混编预制体
,
4D-C/C材料
,
拉伸性能
,
破坏机理
G.C.Ji
金属学报(英文版)
Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterized by evaluation the load/qoad point displacement curves tested by three points bend experiment with single notch beam at 1300℃. The cracks length was determined by compliance calibration curves. It is shown by experimental results that the compliance of 3D-C/SiC composites changes with the cracks can be described by third order polynomial. The variation of crack advancing resistance with non-dimensional equivalent crack length presents a convex curve. The crack advancing resistance increases firstly and then decreases with the non-dimensional equivalent crack length, finally is in comparatively low level. The maximum values of crack advancing resistance are 269.73k J/m^2 for nondimensional equivalent crack length of 0.318 and original notch length of 0.35mm, and 138.65kJ/m^2 for non-dimensional equivalent crack length of 0.381 and original notch length of 2.06mm, respectively.
关键词:
fracture resistance
,
null
,
null
