材料期刊网

Numerical Simulation of Transport Phenomena in Solidification of Multicomponent Ingot Using a Continuum Model

Daming XU , Guangju SI , Geying AN , QingChun LI

材料科学技术（英文）

A continuum model proposed for dendrite solidification of multicomponent alloys, with any partial solid back diffusion, was used to numerically simulate the macroscopic solidification transport phenomena and macrosegregations in an upwards directionally solidified plain carbon steel ingot. The computational results of each macroscopic field of the physical variables involved in the solidification process at a middle solidification stage were presented.

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Mold Filling Behavior of Melts with Different Viscosity under Centrifugal Force Field

Daming XU , Qingmei YU , Xin LI , Geying AN

材料科学技术（英文）

Recently proposed mathematical model for mold filling processes under centrifugal force field conditions and the computer codes were first tested through the sample simulation of gravity mold filling process for a benchmark plate-casting, which were compared with quoted experimental observations. The model and the developed computer program were then applied to the numerical simulation of centrifugal field mold filling processes for a thin-section casting with a titanium alloy melt of assumed viscosity of 1.2 and 12.0 mm2/s, respectively. The computation result comparison shows that the flow behaviors of the filling melts are basically similar to each other although the less viscous melt tends to fill into the thin section casting cavity faster.

关键词: Centrifugal casting , null , null , null

Professor XU Zhong-yu and his research activities

新型炭材料

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On the Indeterminacy in Hardness of Shape Memory Alloys

F.T.Cheng

材料科学技术（英文）

The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.

关键词: Hardness , null , null , null , null , null

Broer-Kaup-Kupershmidt方程的新精确解

杨立娟 , 杨琼芬 , 杜先云

量子电子学报 doi:10.3969/j.issn.1007-5461.2012.02.003

CK方法是求解非线性发展方程的一种有效的直接方法.利用推广的CK方法,求得(2+1)维Broer-Kaup-Kupershmidt方程的Backlund公式,从而获得方程的大量新的精确解,推广了Xu和Zhang的结果.

关键词: 非线性发展方程 , Broer-Kaup-Kupershmidt方程 , 精确解 , CK方法 , Backlund变换

Thermodynamic analyses of strain-induced martensite transformation in Fe-7Mn-1.2C alloy

Jingpei XIE , Yaomin ZHU , Xiaoping WANG

材料科学技术（英文）

The M-s temperature, Delta G(gamma-->alpha), Delta G(gamma-->M) and mechanical energy under a non-severe impact loading in a medium manganese steel (Fe-7Mn-1.2C) have been calculated by means of Xu's Fe-X-C model. The relation between the yield strength of austenite and the driving force for martensite transformation has been established. It is proved that the martensite transformation can take place in a medium manganese steel (Fe-7Mn-1.2C alloy) under a non-severe impact loading.

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磷在12Cr1MoV钢中非平衡晶界偏聚动力学的实验研究

李莉 , 李庆芬 , 郑磊 , 徐庭栋 , 杜善义

钢铁研究学报

以工业用12Cr1MoV钢为研究对象,通过俄歇电子能谱分析方法(AES),对磷在恒温过程中的非平衡晶界偏聚浓度进行了测定.获得的磷在钢中的非平衡晶界偏聚动力学曲线直接验证了非平衡晶界偏聚动力学理论中的Xu-Song模型.

关键词: 晶界偏聚 , 临界时间 , 扩散 , 钢

Shape-Memory Intermetallics Development in Taiwan

S.K.Wu(Institute of Materials Science and Engineering , National Taiwan University Taipei , Taiwan 106 , China) H.C. Lin(Department of Materials Science , Feng-Chia University. Taichung. Taiwan 407. China)

金属学报(英文版)

In Taiwan, many groups engage in the development of TiNi SMAs. The two-stage martensitic transformations of and have been clarified for both TiNi binary and ternary alloys. The deformation behaviors have been investigated by cold-rolling, hot-rolling and wire drawing. Both shape memory effect and pseudoelasticity can be improved by some thermal-mechanical treatments. The damping characteristics of TiNi and TiNiX SMAs have also been systematically studied. Both B19'/B19 martensite (M)and R-phase(R) have high daming capacities due to the stress-induced movement of twin boundaries. Meanwhile, the addition of third elements-Fe and Cu-can largely increase the damping capacity.Recently, some high temperature shape memory alloys-TiHiPd and TiNi-.Au alloys-have also been intensively studied in Taiwan. All these potential investigations on the TiNi SMAs in Taiwan have attracted much attention and their important characteristics will be applied widely in the near future.

关键词: : TiNi shape memory alloys. research and development in Taiwan

磁致双折射和二向色性对磁性液体薄片的光透射率弛豫特性的影响

陆樟献 , 龚雁 , 王渊明 , 王正才 , 陈善飞

功能材料与器件学报 doi:10.3969/j.issn.1007-4252.2012.01.005

基于Xu等人的经典振荡磁偶极子模型和Matsumoto等人给出的双折射驰豫理论,研究了磁致双折射和二向色性对磁性液体薄片的光透射率弛豫特性的影响.理论推导了磁性液体的双折射和二向色性函数的偏振光透射率具体表达式,并进行了数值模拟计算.该问题的研究对磁性液体光学各向异性的深入认识以及相关磁性液体光学器件的应用具有一定的指导意义.

关键词: 物理光学 , 双折射驰豫 , 二向色性驰豫 , 磁性液体 , 磁偶极子

Improving glass-forming ability of Mg-Cu-Y via substitutional alloying: Effects of Ag versus Ni

Journal of Materials Research

Based on the best bulk metallic glass (BMG) forming alloy in the Mg-Cu-Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg-(Cu,Ag)-Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg-(Cu,Ag)-Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg-(Cu,Ni)-Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the "confusion principle."

关键词: bulk metallic-glass;shaped copper mold;amorphous-alloys;thermal-stability;ternary-system;casting method;p system;diameter;zr;mm