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Numerical Simulation of Unidirectional Infiltration of Silicon Carbide Preforms

Xuexi ZHANG , Dezun WANG , Dongyan DING , Congkai YAO

材料科学技术（英文）

Mathematical model of unidirectional infiltration was set up and metal infiltration velocity and temperature fields of the metal, preform, and composites were calculated using the finite difference method. The metal infiltration velocity has a close relationship with infiltration time. It is very large after the infiltration begins in a few seconds, then the velocity keeps almost constant. The temperature field of the composite proves that metal matrix composites (MMCs) after unidirectional pressure infiltration can solidify from the entrance of the preform to the infiltration front, which is useful for obtaining the MMCs with low porosity and high properties.

关键词:

Novel Reduced-friction Materials by Laser Cladding of Copper Alloy on Cast Iron

Xichen YANG Milin ZHONG Tianxi ZHENG Naikun ZHANG Laser Processing Lab. , Tianjin Institute of Textile Science and Technology , Tianjin , 300160 , China

材料科学技术（英文）

Copper alloys suitable for laser cladding on cast iron are selected trom rune types of conventional powders. There are a poor spreading ability and porosity of copper alloy over the surface of castiron. Copper alloy surface is easily oxidized in atmosphere. These shortages have been overcome by ad- ding deoxidizers of Si and H_3BO_3. Laser parameters, stress and coefficient of friction have been ex- amined, and the larger smooth surface of Cu/cast iron for friction by laser cladding has been made for the application of the guide shoes of machine.

关键词: laser cladding , null , null

环氧树脂中电树枝生长特性及其动力学模型的实验验证

杨文虎 , 易冉 , 徐阳 , 惠思思 , 曹晓珑

绝缘材料 doi:10.3969/j.issn.1009-9239.2012.01.014

研究了不同外施工频电压下环氧树脂绝缘中的电树枝结构、生长的特性,并用Ding等提出的模型解释了电树枝的发展过程,模拟了其生长曲线.结果表明:在同一电压下,环氧树脂中电树枝的生长速度基本为恒定值,随外施电压的升高,电树枝分枝变少,生长速度基本呈指数增加,且利用模型模拟的生长曲线与实验测试的结果吻合,最后讨论了模型的物理基础.

关键词: 电树枝 , 环氧树脂 , 劣化 , 动力学 , 模型 , 模拟

Miedema模型在含O和S熔体与合金中的扩展与应用

陈伟亮 , 张宁 , 唐昭辉 , 丁学勇

材料研究学报

将Miedema模型与实验数据相结合得到适于Miedema模型的O和S的参数(O:电负性7.04、电子密度6.03、摩尔体积4.59;S:电负性5.8、电子密度3.24、摩尔体积6.97),计算了141种O的二元化合物和145种S的二元化合物生成焓其平均绝对误差(MAPE)分别为36.8％、32.4％.结合Ding导出的三元系相互作用系数计算模型,计算了1873 K时Fe基熔体中O和S与其它元素之间的相互作用系数.与实验数据的比较表明,除个别元素外,计算值与实验值之间误差不大且变化趋势比较一致.将误差较大的Nb、Ag、Pt的电负性参数由原来的4.05、4.35、5.65修正为4.31、4.17、5.57,使用Miedema模型的计算精度有很大的提高.

关键词: 材料科学基础学科 , Miedema模型 , 含O和S熔体与合金 , 相互作用系数 , 参数的修正

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