材料期刊网

Evaluation of Alpha-case in Titanium Castings

Si-Young Sung , Bong-Jae Choi , Beom-Suck Han , Han-Jun Oh , Young-Jig Kim

材料科学技术（英文）

The alpha-case formation reactions between Ti and investment molds (Al2O3, ZrSiO4, ZrO2, CaO stabilized ZrO2) were evaluated in a plasma arc melting furnace. Regardless of thermodynamic approaches, there were distinct alpha-case formations. The reaction products were characterized by electron probe micro-analysis and transmission electron microscopy. The α-case generation between Ti and Al2O3 mold was not able to be explained by the conventional α-case formation mechanism, which is known to be formed by the interstitials, especially oxygen dissolved from mold materials. However, from our experimental results and thermodynamic calculations, it was confirmed that the α-case is formed not only by an interstitial element but also by substitutional metallic elements dissolved from mold materials. Our newly established α-case formation mechanism will surely lead to a variety of significant applications of the α-case controlled Ti casting.

关键词: Titanium , null , null , null

HAN液晶盒中开关时间对形变场弛豫过程的影响

李晓吉 , 郑桂丽 , 张志东

液晶与显示 doi:10.3788/YJYXS20132801.0025

在HAN液晶盒撤掉外加电压的过程(即弛豫过程)中,假定电压的开关时间为有限的,把电压处理为时间的指数衰减函数.在这一假定下,对撤掉外加电压后HAN液晶盒中指向矢的分布情况进行研究,得到了对HAN液晶盒的弛豫过程有影响的电压开关时间的范围.

关键词: HAN液晶盒 , 有限开关时间 , 驰豫过程 , 动力学理论

电场诱导纳米结构HAN液晶盒中新型有序重构过程的描述

陈思博 , 王永超 , 周璇 , 张志东

液晶与显示 doi:10.3788/YJYXS20163109.0853

基于 Landau-de Gennes 理论，利用松弛迭代的方法，研究了包含－1/2向错线的混合排列(HAN)液晶盒中，平行于向错线的电场所诱导的结构转变。结果表明，盒厚固定时，电场诱导五种结构转变过程；电场固定时，盒厚变化产生三类结构转变方式。力曲线上的极小值确定了液晶系统发生结构转变的临界盒厚。

关键词: 有序重构 , Landau-de Gennes理论 , -1/2 向错 , 力曲线

HAN-IPS液晶盒的引流效应

郑桂丽 , 姜丽 , 张志东

液晶与显示 doi:10.3969/j.issn.1007-2780.2010.06.001

根据Erickson-Leslie流体动力学理论,研究了混合排列向列相-共面转换液晶盒的引流效应.在强锚定边界条件下,经过理论推导,得出液晶指向矢与流速的关系方程,进一步通过数值计算得出指向矢分布与时间的关系.发现引流效应加快了指向矢达到平衡态的速度,而且破坏了指向矢分布的瞬态对称性,特别在加电压的初始几毫秒这种现象非常明显.

关键词: 混合排列向列相 , 共面转换 , 引流效应 , 指向矢分布

Effect of Ni on the formation and thermal behavior of NdAlCo metallic glasses

Yanxin ZHUANG

金属学报(英文版)

Nd₆₀Al{₁₀Co_30-xNi_x (x=0, 5, 10 and 15 at. pct) metallic glasses have been prepared using single-spinner and suck-casting method, and characterized using X-ray diffraction (XRD) and non-isothermal differential scanning calorimetric technique. It has been found that the alloy with 15 at. pct Ni has the strongest glass forming ability, and can be fabricated to a rod with 5 mm in diameter using suck-casting. The addition of Ni has an obvious effect on the thermal behavior of the metallic glasses, especially on the position of the second and third crystallization peaks. The crystallization kinetics and activation energies of the four metallic glasses have been elaborated using the Kissinger equation. The continuous heating transformation curves of the T_x and T_p1 have been constructed by applying the extension of the Vogel-Fulcher-Tammann (VFT) nonlinear equations, which are derived from the experimental data in the heating rate range of 5--80~K/min. The effect of Ni on the formation and thermal stability of the Nd-based metallic glasses has been discussed.

关键词: Nd-based metallic glass

Effect of annealing and heating/cooling rate on the transformation temperatures of NiFeGa alloy

Journal of Alloys and Compounds

In this work, Ni(55)Fe(18)Ga(27) ferromagnetic shape memory alloy was prepared through a suck-casting method. The effects of annealing and heating/cooling rate on the martensitic transformation temperatures were investigated by differential scanning calorimetry (DSC). The results showed that the phase transformation temperatures increase with increasing the annealing temperature, upon the heating and cooling process. However, the start and the finish temperatures (M(s) and M(f)) of martensitic phase transformation increased firstly and then decreased upon the cooling process with the increase the annealing time at 300 degrees C. The start and the finish temperatures (A(s) and A(f)) of inverse phase transformation increased slightly upon the heating process with the increase of the annealing time. The results can be explained by the evolution of the microstructure after heat treatment. It was also found that the phase temperatures show great dependence on the heating/cooling rate of the DSC test, A, and At increased and Ms and Mf decreased with the increase of the heating/cooling rate. (C) 2008 Elsevier B.V. All rights reserved.

关键词: Ni(55)Fe(18)Ga(27) ferromagnetic shape memory alloy;Annealing;Phase;transformation temperature;Heating/cooling rate;shape-memory alloys;ni-mn-ga;field-induced strain;martensitic phase;single-crystals;magnetostriction

弱锚定条件下混合排列向列液晶显示的动态响应

张志东 , 于广 , 张德贤

液晶与显示 doi:10.3969/j.issn.1007-2780.1999.01.002

研究了弱锚定条件下混合排列向列液晶显示的动态响应.具体研究沿面排列处为弱锚定,垂面排列处为强锚定的HAN盒.通过计算液晶盒中的瞬时指向矢分布,得到了透射光强随时间的变化.讨论了响应速度与锚定强度系数之间的关系.

关键词: 混合排列 , 液晶显示 , 弱锚定 , 动态响应

OCB液晶显示的动力学计算

孙玉宝 , 范志新 , 张志东

液晶与显示 doi:10.3969/j.issn.1007-2780.2001.01.006

以液晶动力学理论为基础，考虑引流效应后，计算在强锚定和弱锚定边界条件下的OCB型盒中的指向矢分布和流动速度分布，给出透射光相对强度随时间变化有预倾角情况下的透射光相对强度。计算结果表明，OCB盒较平行排列盒和HAN盒具有更快的响应速度。

关键词: OCB盒 , 响应速度 , 透过率

周期性序列脉冲放电火花点火特性研究

余永刚 , 王玉强 , 周彦煌 , 陆欣

工程热物理学报

为了探索液体火箭发动机的新型点火方法,设计了一种周期性序列脉冲放电火花的模拟点火装置,该装置采用电机驱动电极转动,在圆周上形成放电火花的时空分布.采用高速录像系统,开展了HAN基液体推进剂LP1846液雾在不同条件下电点火特性的实验研究,结果表明,电极转速在3-5 r/s时,电火花在圆周放电空间内的分布比较密集,电能时空分布比较均匀,LP1846液雾点火效果较好.喷雾场流速、液雾细度与周向放电火花能量分布存在一个最佳匹配关系.

关键词: 液体推进剂 , 喷雾 , 电点火 , 瞬态测量

聚丙烯/乙丙橡胶共混体系相分离的流变学表征方法

钱晨 , 杨斌 , 章于川 , 夏茹 , 钱家盛

高分子材料科学与工程

通过动态流变学方法研究了不同配比下聚丙烯/乙烯-丙烯-二烯三元共聚物(PP/EPDM)共混体系相分离行为.结果表明,EPDM与PP相容性不佳,当EPDM质量分数达到20％即已发生相分离,在质量分数为50％时形成双连续相结构,在质量分数50％～60％时发生相反转.采用Cole-Cole曲线、Han曲线、van Gurp曲线等方法表征了PP/EPDM体系相分离行为,其中van Gurp曲线最为敏感.

关键词: 聚乙烯 , 三元乙丙橡胶 , 共混 , 动态流变行为 , 相分离