材料期刊网

Effects of Alloying Elements on the Microstructures and Mechanical Properties of Heavy Section Ductile Cast Iron

G.S.Cho , K.H.Choe , K.W.Lee , A.Ikenaga , null , null , null , null , null , null , null

材料科学技术（英文）

The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of alloy amounts within 0.25 to 0.75 wt pct range. Hardness is measured on the broken tensile specimens. The small additions of Mo, Cu, Ni and Cr changed the as-cast mechanical properties owing to the different as-cast matrix microstructures. The ferrite matrix of Mo and Ni alloyed cast iron exhibits low strength and hardness as well as high elongation and impact energy. The increase in Mo and Ni contents developed some fractions of pearlite structures near the austenite eutectic cell boundaries, which caused the elongation and impact energy to drop in a small range. Adding Cu and Cr elements rapidly changed the ferrite matrix into pearlite matrix, so strength and hardness were significantly increased. As more Mo and Cr were added, the size and fraction of primary carbides in the eutectic cell boundaries increased through the segregation of these elements into the intercellular boundaries.

关键词: Heavy section ductile cast iron , null , null

Effect of Vibrational Modes on Sand Pressure and Pattern Deformation in the EPC Process

A.Ikenaga , G.S.Cho , K.H.Choe , K.W.Lee

材料科学技术（英文）

During the EPC (expendable pattern casting) process, one of the essential requirements is to prevent pattern distortion during sand filling and compaction. A new method which vibrates the system in a two-dimensional circular mode has been applied to the EPC process. The molding properties of unbonded sand obtained by this new vibration mode are investigated and compared with those in the one-dimensional vertical mode. For adequate compaction of sand, the circular vibration mode is more effective than the vertical mode. Sand became more fluidized by the circular vibration and the particle pressure coefficient was close to unity. The particle pressure coefficient, which is defined as the ratio of horizontal to vertical sand pressure, is responsible for the effectiveness of sand filling.

关键词: EPC process , null , null , null , null

Effect of Applied Pressure on the Joining of Combustion Synthesized Ni3Al Intermetallics with Al Alloy

G.S.Cho , J.H.Yang , K.H.Choe , K.W.Lee , A.Ikenaga

材料科学技术（英文）

We focused on the surface reinforcement of ligth weight casting alloys with Ni-Al intermetallic compounds by in-situ combustion reaction to improve the surface properties of non-ferrous casting components. In our previous works, green compact of elemental Ni and Al powders were reacted to form Ni3Al intermetallic compound by SHS (Self-propagating high temperature synthesis) reaction with the heat of molten Al alloy and simultaneously bonded with Al casting alloy. But some defects such as tiny cracks and porosities were remained in the reacted compact. So we applied pressure to prevent thermal cracks and fill up the pores with liquid Al alloy by squeeze casting process. The compressed Al alloy bonded with the Ni3Al intermetallic compound was sectioned and observed by optical microscopy and scanning electron microscopy (SEM). The stoichiometric compositions of the intermetallics formed around the bonded interface and in the reacted compact were identified by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). Si rich layer was formed on the Al alloy side near the bonded interface by the sequential solidification of Al alloy. The porosities observed in the reacted Ni3Al compact were filled up with the liquid Al alloy. The Si particles from the molten Al alloy were detected in the pores of reacted Ni3Al intermetallic compact. The Al casting alloy and Ni3Al intermetallic compound were joined very soundly by applying pressure to the liquid Al alloy.

关键词: Joining , null , null , null , null

K-RE变质处理改善Fe-V-W-Mo合金性能的研究

符寒光 , 李定 , 邢建东

稀有金属材料与工程

研究了K-RE变质处理对Fe-V-W-Mo合金机械性能和热物理性能的影响.结果发现,Fe-V-W-Mo合金经K-RE变质处理后,硬度和红硬性略有增加,冲击韧性提高41.82%,达到11.09J/cm2,耐磨性和导热系数提高,热膨胀系数减小.分析了K-RE改善Fe-V-W-Mo合金性能的机理,并制造了K-RE变质Fe-V-W-Mo合金轧辊,在热轧生产中使用获得了良好的效果.

关键词: K-RE变质处理 , Fe-V-W-Mo合金 , 机械性能 , 物理性能 , 轧辊

6W@60K脉管制冷机的优化及实验研究

张安阔 , 吴亦农 , 刘少帅 , 蒋燕阳 , 蒋珍华 , 陆志

工程热物理学报

设计制作了一台6W@60K同轴型脉管制冷机,用于冷却一碲镉汞红外探测器.通过脉管制冷机结构特点的分析及系统阻抗特性的研究,给出压缩机内部气体阻抗实虚部与PV功转换效率之间的变化规律,从而为设计出高效的脉管制冷机提供有益指导.完成了该脉管制冷机的设计、制作及性能测试工作.实验表明该制冷机在150 W电功输入下可获得低于40 K最低温度,195 W电功输入下60 K可获得6W制冷量,比卡诺效率为12％.

关键词: 脉管制冷机 , 6W@60K , 阻抗

35K／0．6W多路旁通单级脉冲管制冷机

杨俊玲 , 蔡惠坤 , 杨鲁伟 , 周远

工程热物理学报

针对35K温区应用这一制冷要求，围绕多路旁通方案高频同轴脉冲管制冷机这一拥有我国自主知识产权的技术开展了系统的实验研究。实验表明多路旁通流通面积和惯性管长度都有最佳值，是关键影响因素；引入双向进气后，制冷剂温度降低10K左右，是35K应用不可缺少的因素。实验表明多路旁通优于传统单级和二级的形式。在原理样机阶段，实现了200W输入功率下最低温度2叠1K，0．6W／35K的性能。在此基础上，完成了另一套全焊接结构的实用样机的研制，测试得到了200W输入功率下O5W／34K的性能。这一工作的顺利开展代表了高频多路旁通方案实用化的突破，为我国35K高频微型低温制冷机的研制奠定了基础。

关键词: 多路旁通 , 高频脉冲管制冷机 , 同轴 , 35 , K温区

Densification of the Tungsten Heavy Alloys at 1473 K and Fabrication of W-Mo System FGM with Density Gradient

Huaping XIONG , Lianmeng ZHANG , Junguo LI , Runzhang YUAN

材料科学技术（英文）

The tungsten heavy alloys with Ni-Al and Fe-Al additives were sintered by hot-press method at 1473 K for 1 h. It was found that the relative density of the W-Fe alloy could be increased evidently by addition of Al. However, the relative density of W-Ni-Al alloy with low content of Al was conversely decreased considerably compared with that of W-Ni alloy. The causes have been studied. The sintering experiments of Mo alloy and W-Mo alloys with 3 wt pct Fe-1.5 wt pct Al additives were also carried out under the same sintering condition of low temperature. Finally, W-Mo system FGM with density gradient was successfully fabricated. Its density changed gradually from 17.0´103 kg/m3 to 9.5´103 kg/m3 within the middle 1.1 mm thickness range.

关键词:

0.2 W@20.6 K单级高频脉冲管制冷机研究

陈六彪 , 金海 , 朱文秀 , 王俊杰 , 周远 , 顾开选 , 季伟

工程热物理学报

本文介绍一台单级高频脉冲管制冷机的实验结果,研究了充气压力、运行频率、热端温度及冷头朝向等参数对制冷机性能的影响.该制冷机采用多路旁通方案、同轴结构,联合采用双向进气和惯性管气库进行调相.长颈管穿过压缩机内部后密封在气库里,气库、压缩机与脉冲管耦合成一体,结构紧凑.在充气压力1.7 MPa,输入电功260 W时,能够在20.6 K获得0.2 W,在24.1 K获得0.5 W的制冷量;在268 W输入电功,38 Hz运行频率条件下,无负荷最低温度18.6K是单级高频脉冲管制冷机在国际上首次获得的最低温度.

关键词: 单级 , 多路旁通 , 高频 , 20 K

Subsolidus phase relations in the systems K2O-ZnO-AO(3) (A = Mo, W)

Journal of Alloys and Compounds

The subsolidus phase relations of the systems K2O-ZnO-AO(3) (A= Mo, W) have been investigated by X-ray diffraction (XRD) analyses. The phase diagrams have been constructed. There are six binary compounds and two ternary compounds in the K2O-ZnO-MoO3 system, it can be divided into 11 three-phase regions. The K2O-ZnO-WO3 system consists of six binary compounds and one ternary compound. This system can be divided into 9 three-phase regions. DTA results indicated the compounds K2MOO4 and K2WO4 are not suitable to be fluxes for ZnO crystal growth. (c) 2006 Elsevier B.V. All rights reserved.

关键词: ZnO;x-ray diffraction;phase diagram;DTA;crystal growth;zno single-crystals;hydrothermal growth;zinc oxide;potassium;polymolybdates;polytungstates;diffraction;vapor

K-RE变质处理改善Fe-V-W-Mo合金组织

符寒光 , 邢建东 , 李言祥

稀有金属材料与工程

用K-RE对Fe-5%V-5%W-5%Mo-5%Cr-3%Nb-2%Co-2%C合金变质处理,使凝固组织发生了明显的变化,不仅碳化物和基体组织明显细化,还出现共晶碳化物断网现象,产生了较多的小块状和颗粒状碳化物.经K-RE变质处理Fe-V-W-Mo合金加热温度950℃时,碳化物断网明显,加热温度1 000℃时,多数碳化物已断网,并出现了数量较多的颗粒状碳化物,加热温度1 050℃时,碳化物网状组织全部消失,大部分碳化物变成了球状组织.

关键词: 变质处理 , K-RE , Fe-V-W-Mo合金 , 共晶碳化物 , 团球化