超重和对铅锡共晶凝固组织的影响

采用臂长为１．３ｍ的离心机实现１、５、１０、１５ｇ（１ｇ＝９．８ｍ·ｓ＾－２）四个重力水平，利用Ｂｒｉｄｇｍａｎ法使Ｐｂ－Ｓｎ共晶单向凝固。以观察重力对凝固组织的影响。结果表明，随重力水平的提高，共晶昌团尺寸减小，而共晶相间距不变，表明浮力对流不影响共晶相间的溶质交换。     

倒装芯片互连时SnAg／95Pb5Sn焊料间的互扩散行为及Ni阻挡层的作用

本文研究了共晶ＳｎＡｇ／９５ＰｂＳｎ扩散偶在２５０℃下的扩散行为。发现由于９５Ｐｂ５Ｓｎ中的Ｐｂ向熔融共晶ＳｎＡｇ焊料中扩散而部分生成三元共晶Ｐｂ－Ｓｎ－Ａｇ相,其熔点约为１７８℃。化学镀Ｎｉ层可以有效地防止共晶ＳｎＡｇ和９５Ｐｂ５５ｎ间的互扩散,防止Ｐｂ－Ｓｎ－Ａｇ共晶相的生成,从而提高焊点的耐热温度。文中还研究了与共晶ＳｎＡｇ／Ｎｉ／９５Ｐｂ５Ｓｎ结构相关的相变及力学性能。     

凝固界面临界分叉—Sn—Pb共晶定向凝固几何模型

数值求解了Ｓｎ－Ｐｂ共晶定向凝固静态耦合方程。详细讨论了三相交接点处过冷，界面形态及界面分叉特征作为共晶相间距的函数待征。计算发现三相交接点处最小过冷、β（Ｐｂ）相凝固界面形态临界分叉及此界面中心位置极大值三者是一一对应的。提出了共晶定向凝固几何模型并导出了谱适标度律：λ－Ｖ＾－１／２．ｆ（Ｇｉ／Ｖ），这里λ为共晶相间距，Ｃｌ为温度梯度。ｆ是凝固速度Ｖ的增函数并在Ｖ很高时趋于饱和。将这一标度律同现     

凝固界面临界分叉－Sn－Pb共晶定向凝固几何模型

数值求解了Ｓｎ－Ｐｂ共晶定向凝固静态耦合方程．详细讨论了三相交接点处过冷、界面形态及界面分叉特征作为共晶相间距的函数特征．计算发现三相交接点处最小过冷、β（Ｐｂ）相凝固界面形态临界分叉及此界面中心位置极大值三者是一一对应的．提出了共晶定向凝固几何模型并导出了普适标度律：λ～Ｖ－１／２·ｆ（ＧＬ／Ｖ），这里λ为共晶相间距，ＧＬ为温度梯度，ｆ是凝固速度Ｖ的增函数并在Ｖ很高时趋于饱和．将这一标度律同现有试验结果进行了比较     

电沉积可焊性光亮锡—铅合金的研究

提出了一种电积可焊性光亮Ｓｎ－Ｐｂ合金的新工艺。研究结果表明：Ｐｂ＾２＋浓度、溶液温度、阴极电流密度和光亮剂的含量对合金沉积层中Ｐｂ含量有较大影响。在给定的工艺条件下，可得到含Ｐｂ量为１０％左右、可焊性良好的光亮Ｓｎ－Ｐｂ合金沉积层。     

电沉积可焊性光亮锡－铅合金的研究

提出了一种电沉积可焊性光亮Ｓｎ－Ｐｂ合金的新工艺。研究结果表明：Ｐｂ２＋浓度、溶液温度、阴极电流密度和光亮剂的含量对合金沉积层中Ｐｂ含量有较大影响。在给定的工艺条件下，可得到合Ｐｂ量为１０％左右、可焊性良好的光亮Ｓｎ－Ｐｈ合金沉积层。     

双金属复合材料双结晶器连铸工艺研究

总结了双金属连铸技术的研究开发现状，提出了双金属复合材料双结晶器一次铸造连续成形新工艺。以Ｐｂ和Ｐｂ－Ｓｎ共晶合金作为试验材料，在自行设计和制造的双结晶器连铸试验样机上进行了成形试验。结果表明：本文提出的双金属复合材料双结晶器一次铸造连续成形新工艺是可行的；采用该工艺成功地制备了内坯Ｐｂ与包覆金属Ｐｂ－Ｓｎ合金之间为冶金结合的复合材料；影响连铸复合材料质量的主要因素是两种金属的浇注温度和拉坯速度。     

氮对纳米硅氮薄膜晶化的影响

在电容式耦合等离子体化学气相沉积系统中，用高氢稀释硅烷和氮气为反应气氛制备纳米硅氮（ｎｃ－ＳｉＮｘ２Ｈ）薄膜，结果表明，当Ｎ２／ＳｉＨ４气体流量比（Ｘｎ）从Ｉ增加为４时，薄膜的晶态率从５８％降至１４％，晶粒尺寸从１０ｎｍ降至５ｎｍ，Ｎ／Ｓｉ含量比从０．０３增至０．１２，当Ｘｎ≥５，则生成非晶硅氮（ａ－ＳｉｕＮｘ２Ｈ）薄膜，当Ｘｎ从１增加为１０时，薄膜暗电导率从１０＾－５（Ωｃｍ）＾－１降至１０＾－     

氮对纳米硅氮薄膜品化的影响

在电容式耦合等离子体化学气相沉积系统中，用高氢稀释硅烷和氮气为反应气氛制备纳米硅氮（ｎｃ－ＳｉＮｘ：Ｈ）薄膜结果表明：当Ｎ＿２／ＳｉＨ＿４气体流量比（Ｘｎ）从１增加为４时，薄膜的晶态年从５８％降至１４％，晶粒尺寸从１０ｎｍ降至５ｕｍ，Ｎ／Ｓｉ含量比从０．０３增至０．１２．当Ｘｎ≥５，则生成非晶硅氮（ａ－ＳｉＮｘ：Ｈ）薄膜．当Ｘｎ从１增加为１０时，薄膜暗电导率从１０￣（－５）（Ωｃｍ）￣（－１）降至１０￣（－１１）（Ωｃｍ）￣（－１），具有逾渗行为，这与薄膜的晶态率紧密相关．     

Ti／SnO2＋Sb2O3／PbO2电极的电催化性

本文研制了一种阳极－Ｔｉ／ＳｎＯ２＋Ｓｂ２Ｏ３／ＰｂＯ２，考察了该电极在２．５ＭＨ２ＳＯ４中不同温度下的电解使用寿命，测定了该电极的极化曲线和电化学动力学参数ａ、ｂ、ｉ。讨论了ＰｂＯ２电极的析氧机理和酚氧化的催化性，结果表明该电极的电催化性能优良。     

超重力对铅锡共晶凝固组织的影响

采用臂长为1．3m的离心机实现1、5、10、15g（1g=9．8m·s-2）四个重力水平；利用Bridgman法使Ph－Sn共晶单向凝固，以观察重力对凝固组织的影响结果表明，随重力水平的提高，共晶晶团尺寸减小，而共晶相间距不变，表明浮力才流不影响并晶相间的溶质交换     

Lamellar Spacing Selection in Regular Eutectic Solidification at Low Velocity

Based on the Jackson and Hunt＇s analysis, the selection of lamellar spacing in regular eutectics was reexamined at low velocity. The isothermal assumption was released and the effective interface undercooling was determined by the weighted average of the eutectic phases. It is found that the lamellar spacing minimized the effective interface undercooling depends only on the intrinsic characteristics of a given system at a fixed velocity. In addition, the selection of lamellar spacing is related to the relationship between the average interracial undercoolings of the eutectic phases and the lamellar spacing. The selected lamellar spacing obviously deviated from that predicted by the Jackson and Hunt＇s analysis if the variation of the average interracial undercoolings of the solid phases with the lamellar spacing was markedly different at a constant growth rate.     

Microstructure development in eutectic Al–Fe alloy during directional solidification under high magnetic fields at different growth velocities

In this study, the Al-1.9 wt.% Fe alloy was directionally solidified at different growth velocities under various high magnetic fields. The effect of high magnetic fields on microstructural evolution of the alloys during directional solidification and their dependence on the growth velocity were investigated. The microstructures near the transition growth regions of the alloys between two different growth velocities were observed. With increasing growth velocity, the microstructure exhibited a eutectic to cellular eutectic to hypoeutectic structure transformation. Applying high magnetic fields increased the spacing of the eutectic Al₃Fe phase and decreased the alignment degree of the eutectic Al₃Fe phase at 1 µm/s, decreased the size of the eutectic cells at 10 µm/s, and promoted development and branching of the primary Al dendrites at 100 µm/s. Near the transition growth region, applying high magnetic fields stopped the growth of existing eutectic Al₃Fe and promoted nucleation of the new eutectic Al₃Fe phase for 1–10 μm/s, and accelerated transformation of the growth behavior from cellular eutectic to hypoeutectic for 10–100 μm/s. The evolution of the eutectic growth behavior caused by the high magnetic fields can be attributed to suppression of convection and the corresponding decrease in solute migration owing to the Lorentz force.

     

Mechanical properties characterization of the Pb-Cd eutectic composite

The tensile and compressive properties of the unidirectionally solidified Pb-Cd eutectic have been examined and compared with those of the Cd-Zn eutectic. In spite of the fact that these two eutectic composites contain volume fractions of almost identical (h c p) reinforcing phase, the former exhibited poor mechanical properties. This has been attributed principally to the relatively lower UTS of the Cd lamellae and to the lower shear strength of the Pb-rich matrix. Off-eutectic alloys showing a coupled eutectic microstructure did not show any appreciable increases in mechanical properties even when grown at lower growth rates where a regular lamellar structure was obtained.     

稀土元素(La,Sm,Tb)合金化铌硅材料显微组织及室温断裂韧度EI北大核心CSCD

采用真空非自耗电弧熔炼制备添加稀土元素的Nb-20Ti-16Si-3Al-3Cr-2Hf合金纽扣锭,稀土元素为不同含量的Sm,La,Tb。对铸态合金进行微观组织分析和室温断裂韧度测试。结果表明:合金主要由(Nb,Ti)相与Nb5Si3相组成,不同部位存在多种微观组织,粗大的两相组织存在宏观聚集现象;纽扣锭中普遍存在规则的共晶晶胞和以Nb5Si3相为核心的板条状晶胞;共晶晶胞中心为Nb5Si3相和铌固溶体相Nbss组成的层片状组织,外围为粗大的"齿状"两相组织;板条状晶胞的Nb5Si3相核心保留了完整的平直界面和规则的棱角,晶胞外围主要由细小网状的硅化物和粗大的树枝状Nbss相组成。使用多元线性回归分析不同稀土含量与合金室温断裂韧度的关系,不同稀土含量的合金室温断裂韧度值分布在11~15MPa·m^(1/2)之间,多元线性逐步回归分析后得到室温断裂韧度Kq与稀土含量(Sm,La,Tb)的关系为Kq=10.344+6.896La+2.993Sm。     

激冷快速凝固Al-Cu共晶合金的层片失稳研究

目的 研究热处理条件下共晶层片组织的失稳机制,通过理论建模定量阐明控制层片失稳的关键因素。方法 以Al-Cu共晶合金为研究对象,采用铜模激冷的方法使合金发生激冷快速凝固,获得2个不同冷却速率下的细化共晶层片组织,进一步对所制备的样品进行不同温度及时间的退火处理。研究了退火条件下层片组织的失稳行为,进一步建立了层片失稳的理论解析模型,并基于模型,阐明了热处理条件下共晶层片失稳的机制。结果 凝固冷速为63 K/s和28 K/s的2个样品层片组织均发生了失稳,且在相同退火温度下,冷速为63 K/s的样品(初始共晶层片更细小)更易发生失稳,当退火温度及时间相同时,冷速为63 K/s的样品层片失稳程度更高。结论 在退火条件下,受瑞利不稳定性的影响,共晶层片失稳遵循由层片组织转为棒状组织、棒状组织转变为粒状组织的演变规律;层片厚度和退火温度是层片粒化的主要影响因素。     

Study on the Relationship between Lamellar Spacing and Growth Rate inthe Regular Eutectic Growthby Monte-Carlo Simulation

A modified Monte-Carlo(MC) method to simulate the regular growth of binary eutectic alloys is presented. It is found that the growth rate has a linear dependence on the chemical potential difference between the solid and liquid; the relation between the lamellar spacing A and growth rate R accords well with the prediction of Jackson-Hunt(JH) theory unless the growth rate is very low.     

The microstructure of unidirectionally solidified Ag-Ge eutectic alloys

Ag-Ge alloys containing 15 to 22 wt% Ge were unidirectionally solidified to investigate the growth conditions for fully eutectic growth (the coupled region) in the range of growth rate 1.4 x 10^–4 to 1.1 cm sec^–1 and at a temperature gradient of 200° C cm^–1. Primary silver was not formed in the hypereutectic Ag-Ge alloys, implying that the coupled region of Ag-Ge alloys may be different from that of the other nf-f alloy systems such as Al-Si, Fe-C, Al-Ge and Al-Fe, whose coupled regions are usually skewed towards the faceted component. It was also observed that the morphologies of primary silver, primary germanium and eutectic structure were changed with increasing growth rate. Lamellar colonies were formed prominently in the fast-grown hypereutectic alloys. As the growth rate increased the tendency for branching in massive primary germanium was so pronounced that a lamellar colony was finally formed.     

Study on the Relationship Lamellar Spacing and Growth Rate in the Regular Eutectic Growth by Monte—Carlo Simulation

A modified Monte-Carlo(MC) method to simulate the regular growth of binary eutectic alloys is presented.It is found that the growth rate has a linear dependence on the chemical potemtial difference between the solid and liquid ,the relation between the lamellar spacing λ and growth rate R accords well with the prediction of Jackson-Hunt(JH) theory unless the growth rate is very low.