材料期刊网

Properties of Dispersion Casting of Y2O3 Particles in Hypo, Hyper and Eutectic Binary Al-Cu Alloys

J.J.Park , G.H.Kim , S.M.Hong , S.H.Lee , M.K.Lee , C.K.Rhee

材料科学技术（英文）

In the present work, the dispersion casting of Y2O3 particles in aluminum-copper alloy was investigated in terms of microstructural changes with respect to Cu contents of 20 (hypo), 33 (eutectic) and 40 (hyper) wt pct by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For the fabrication of Al-Cu alloy dispersed Y2O3 ceramic particles, stir casting method was employed. In case of Al-20 wt pct Cu alloy (hypoeutectic), SEM images revealed that primary Al was grown up in the beginning. After that, eutectic phase with well dispersed ceramic particles was formed. In case of eutectic composition, Y2O3 particles were uniformly dispersed in the matrix. When the Cu is added into Al up to 40 wt pct (hypereutectic), primary θ phase was grown up without any Y2O3 ceramic particles in the early stage of solidification. Thereafter, eutectic phase was formed with well dispersed ceramic particles. It can be concluded that Y2O3 ceramic particles is mostly dispersed in case of eutectic composition in Al-Cu alloy.

关键词: Dispersion casting , null , null , null

Secondary M6C precipitation in K40S cobalt-base alloy

Materials Letters

Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词: M6C precipitation;aging;M7C3 carbide;superalloy

裂纹顶端位错的运动和小范围屈服的K_(Ⅱc)

龙期威 , 高桦

金属学报

本文从裂纹顶端位错运动的简化模型估计形成塑性区所消耗的功;从而计算临界裂纹扩展力。由于Ⅰ型加载和Ⅱ型加载的应力状态有所不同,裂纹顶端塑性功耗也会不一样。基于上述思想,考虑了小范围屈服的K_(Ⅰc)和K_(Ⅱc)的关系,得出K(Ⅱc)>K(Ⅰc)的结论,符合实验结果;并就K(Ⅱc)/K(Ⅰc)的比值与材料性能和温度的关系作了讨论。

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Zn-5%Al合金超塑性的m-C-δ(或m-k-δ)关系

刘勤 , 夏锄 , 刘晓东

金属学报

在170,190,210,230,250℃的温度下,采用3.7×10~2,7.4×10~2和1.1×10~(-1)min(-1)的应变速率(平均)对Zn-5%Al共晶合金的m-C-δ(或m-k-δ)关系曲线(简称m-δ关系曲线)进行了测定.所有的曲线均随应变的δ增加而快速上升.俟达到某一定的应变量(极限应变量δ1)后。开始缓慢下降并保持平稳直至断裂.Zn-5%A1共晶合金的m-δ关系曲线不存在k_(?)=k_I(k_(I 1),k_(I 2),k_(I 3),……)=k_F(或C_0=C_I(C_(I 1),C_(I 2),C_(I 3),……)=C_F=1)的简单情况.可应用m-δ方程式[4,5]对曲线上各点C值(包括所有的C_I和C_F值)进行计算.C值随δ值的增加成近似的直线上升.直线的斜率在极限应变(δ1)处突然减小.

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Prediction and improvement of mechanical properties of corrosion resistant superalloy K44 with adjusting minor additions C, B and Hf

Materials Transactions

The neural network (NN) method is applied to predict the influence of minor additions C, B and Won mechanical properties of cast superalloy K44 with heat treatment parameters considered. Furthermore, the influence of minor additions C B and Hf on phase stability is estimated using d-electrons theory. The results from these two methods indicate that decreasing C content, increasing B content and doping 0.2-0.3 mass% Hf can balance the desired mechanical properties and phase stability in K44 alloy, which also is confirmed experimentally through the relation between mechanical properties and phase stability of base/modified K44 alloys.

关键词: superalloy K44;neural network;d-electrons theory;mechanical;properties;phase stability;bayesian neural-network;nickel-base superalloys;creep-rupture life;behavior;phase

Cyclic oxidation behavior of glass-ceramic composite coatings on superalloy K38G at 1100 degrees C

Thin Solid Films

The SiO(2)-Al(2)O(3)-ZrO(2)-CaO-ZnO glass-ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass-ceramic coatings and the NiCoCrAlY coatings were about 10 mu m and 20 mu m, respectively. Cyclic oxidation tests were carried out at 1100 degrees C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass-ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 degrees C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass-ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass-ceramic coatings. (C) 2011 Elsevier B.V. All rights reserved.

关键词: Glass-ceramic coating;NiCoCrAlY;Cyclic oxidation;Magnetron sputtering;resistance;microstructure;scales

Ni在熔融(Li,K)2C03中的腐蚀行为

王文 , 曾潮流 , 吴维

腐蚀学报（英文） doi:10.3969/j.issn.1002-6495.1999.06.006

采用电化学阻抗谱技术研究了Ni在650 C熔融(Li,K)2CO3中的腐蚀行为.在自腐蚀电位下,Ni的腐蚀电化学阻抗谱呈典型的扩散控制特征,表面形成疏松的氧化膜,腐蚀速度较快.提出了相应的等效电路,求得相关电化学参数,

关键词: Ni熔融碳酸盐电化学阻抗谱熔盐热腐蚀

K2SiO3/C颗粒催化大豆油酯交换制备生物柴油

王建勋 , 陈洸艟 , 陈锦章

催化学报 doi:10.1016/S1872-2067(10)60265-3

采用浸渍法将钾水玻璃负载于碳颗粒(粒径1～3.5 mm)上,经120℃烘干后制得K2SiO3/C催化剂.以X射线衍射、扫瞄电镜-能量色散X射线与Hammett指示剂等方法对样品进行了表征.以K2SiO3/C为催化剂,大豆油为原料,进行酯交换反应制备生物柴油,考察了催化剂用量、醇/油摩尔比、反应时间(微波与传统加热)等因素对大豆油酯交换率的影响.当醇/油摩尔比30∶1,催化剂用量24 wt％时,传统加热反应于2.5 h达到96.5％酯交换率,而相同条件下微波加热反应于1.5h达到96.7％酯交换率.

关键词: 生物柴油 , 固体催化剂 , 钾水玻璃 , 碳颗粒 , 微波吸收

K3C60晶体中钾离子的平衡位置

刘红 , 陈宗璋 , 彭景翠 , 陈小华 , 白晓军

无机材料学报 doi:10.3321/j.issn:1000-324X.2000.03.004

分析八面体空隙中心碱金属的相互作用势能, 研究碱金属沿[111]、[110]和[100]三个不同方向移动时, 势能的变化情况, 结果表明, 对于K3C60晶体, K+离子在三个不同方向上都存在非中心平衡位置, 而且在三个不同方向上, 非中心平衡位置相对中心的偏移量不同, 在[111]轴上为0.98, 在[110]轴方向上为0.78, 在[100]方向上为0.56, 在[111]轴方向的非中心的势能是最小值, 为-508.59meV.通过对计算结果的分析, 认为非中心平衡位置的出现应归因于短程相互作用, 其中与C60的相互作用是最主要的, 其势能最低点对应的位置不在中心;三个不同方向的非中心平衡位置偏离中心距离不同, 是因为与之对应晶面上的C60面密度不同.

关键词: K3C60晶体 , 非中心格点 , 八面体对称性 , Lennard-Jones势 , 晶面

一种改进的C-V方法对向列相液晶弹性常数k11、k33测量的理论研究

孔祥建 , 荆海 , 黄霞 , 廖燕平 , 刘金娥

液晶与显示 doi:10.3969/j.issn.1007-2780.2007.05.017

提出了一种更为准确的测量向列相液晶展曲、弯曲弹性常数的C-V方法.以正性液晶材料为例,当沿面排列的液晶分子预倾角不为零时,阈值电压值不易确定, k11的确定必定存在误差,而以前报道并未考虑到此问题.文章针对此问题给出了在强锚定条件下,预倾角不为零时C-V的关系式,并提出了通过曲线拟合来同时确定弹性常数k11、k33的方法.此方法对弹性常数的测量更为准确,液晶盒的制作要求降低,且测试简单、易操作.

关键词: 向列相液晶 , 电容-电压 , 弹性常数 , 预倾角 , 曲线拟合