W. Chen
,
Y.Z. Zhang
,
C.J. Zhang
,
L.G. Zhu
金属学报(英文版)
The aim of this study is to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method is used in the heat conduction equation. The thermo-mechanical property in the mushy zone is taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell has its maximum value at the flange tip and its minimum value at the fillet. The temperature has a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web is in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually move to the internal section of the flange tip and the web. However, whenever, there are bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.
关键词:
beam blank
,
null
,
null
,
null
W. Chen
,
D. Fergson and H. Ferguson (Dynamic Systems Inc. Poestenkill
,
NY 12140
,
USA)
金属学报(英文版)
There is a considerable interest in developing methods for processing of materials with ultrafine grain si- zes. Widely used methods in refining microstructure are severe/intense plastic deformation techniques, such as torsion straining, equal channel angular (ECA) pressing/extrusion,and accumulative roll bonding (ARB) technique.While the torsion technique has been available for decades,a new torsion system has been developed at DSI for simulation of complex stress states such as combination of shear and compression or shear and tension stress states. The equal channel angular pressing technique is ma- inly used for production of ultrafine grain aluminum alloys,which is aimed at develoment of high strain rate superplasticity.The accumulative roll bonding technique has been applied for the rolling of both aluminum alloy and steels to produce ultrafine gained materials. Three different types of hot compression deformation methods, each with a different number of deforma- tion axis, are introduced in this paper. They are single axis deformation, two axis deformation and three axis deformation.The single axis deformation has us or little restraint such as plane strain type testing and axisymmetric compression testing, the two - axis deformation can be fully restrained or un- restrained, and the three - axis deformation has no restraint. The two - axis restrainsd compression deformation techopue is recommended for loboratory side after comparing the single - axis and the three - axis deformation techniques since the bulk volume of the two - axis restraint compression speci- men can be easily machined into mechanical testing speciments for mechanical property measurement and other studies,and the technique can be aplied to studies of any metallic materials.
关键词:
ultrafine grain
,
null
李开明
,
李亚洲
,
冯维贵
,
林长
量子电子学报
doi:10.3969/j.issn.1007-5461.2007.05.014
采用非线性反馈控制,用附加了带参数的正弦项对Chen系统进行了有效的控制.随着参数k的逐渐增大,系统的动力学行为呈现出一系列的变化.数值研究结果表明:随控制参数的增大,驱动信号的强度渐大,混沌系统由混沌运动到周期轨道,最终到一相点.
关键词:
混沌
,
Chen系统
,
不动点
,
Lyapunov指数
,
反馈控制
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
于荣
,
贺连龙
,
程志英
,
朱静
,
叶恒强
金属学报
doi:10.3321/j.issn:0412-1961.2002.z1.140
用高空间分辨分析电子显微术研究了TiAl-W-Si合金中B2相的析出行为和元素W的分布.结果表明,α2/γ相界面台阶由于W的富集而成为B2析出相的择尤形核位置.B2相中,高达三分之一的Al原子被W原子置换,而在γ相中只固溶了很有限的W.另外,W也偏析在α2/γ和B2/γ相界面上.这些结果合理地解释了W对提高TiAl合金蠕变性能的显著作用.
关键词:
分析电子显微术
,
TiAl
,
析出相
,
偏析
Journal of Physics D-Applied Physics
The effect of Co addition combined with W on the microstructure and magnetic properties of nanocomposite magnets with composition of (1 - x wt%)Nd8.55Fe84.49W0.60 B-0.636 + x wt% CO, prepared by mechanical alloying, has been investigated. The addition of W can increase the unit cell volume of soft and hard phases in nanocomposite: magnets, and cause the anisotropy field of the hard phase component to increase. Therefore, the addition of W can improve coercivity. On the other hand, addition of Co leads to a decrease of the grain size of the alpha-Fe soft phase component in nanocomposite magnets annealed at temperatures lower than 670 degrees C. It leads further to a decrease of the optimal annealing temperatures, an increase of the remanence and maximum magnetic energy product, and a slight decrease of the coercivity. With increasing the content of Co, the dependence of remanence J(r) on annealing temperature T-a changes from a convex shape, giving a maximum, to a monotonically decreasing one. These phenomena have been explained in terms of the variation of grain growth and exchange coupling between the grains, due to the addition of Co and W.
关键词:
nd-fe-b;remanence enhancement;alloys;phase;microstructure;nb
HUANG Huimin CHEN Xinmin Central South University of Technology
,
Changsha
,
China HUANG Huimin Associate Professor
,
Department of Chemistry
,
Central South University of Technology
,
Changsha
,
China
金属学报(英文版)
The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly chemisorbed oxygen and the interstitial oxygen which could form an interstitial solid solution with β-W.It seems better to consider β-W to be a metastable phase of tungsten with the interstitial oxygen as stabilizer.
关键词:
tungsten
,
null
,
null
,
null
黄远辉
,
杨海涛
,
尚福亮
,
吴国根
,
汪晓
稀有金属材料与工程
用高温固相反应法制备出A_2W_3O_(12) 型稀土钨酸盐材料(A=Y,Er,Ho,Yb),用室温及高温XRD测定其在不同温度下的结构、晶胞参数及晶胞体积,并用TOPSA软件对其结构进行精修.发现除HO_2W_3O_(12)外,都具有较大的负热膨胀系数.据A. W. Sleight预测,HO_2W_3O_(12)具有较大的负热膨胀特性,但本实验却发现它并没有负热膨胀性,反而具有非常大的正热膨胀系数.
关键词:
稀土钨酸盐
,
高温XRD
,
HO_2W_3O_(12)
韩兵强
,
李楠
材料科学与工程学报
doi:10.3969/j.issn.1673-2812.2003.06.020
以铝热法为基础制备了Al2O3/W复合材料,探讨了Al2O3含量对复合材料合成的影响.研究表明:主要物相为α-Al2O3、金属W.刚玉含量小于0 3时,温度影响不显著,大于0 3时,温度影响显著,有大量碳化物生成,且WC/W2C相对含量随Al2O3含量增加及煅烧温度的提高而增加.当刚玉含量为0 5mol时,有正交晶钨酸铝生成.随刚玉含量变化,金属钨分布从连续分布向弥散分布变化.连续分布的金属钨因被氧化铝包裹因此难以碳化,而弥散分布的金属钨则易于被碳化.
关键词:
铝热反应
,
相组成
,
显微结构
,
碳化
