混合稀土含量对Zn9.3Al7Cu合金钎料润湿性能及显微组织的影响

在Zn9.3Al7Cu合金钎料中添加了质量分数分别为0,0.1%,0.3%,0.5%的由镧粉和钕粉组成的混合稀土,研究了混合稀土含量对该合金钎料熔点、润湿性能、显微组织,以及对其钎焊铜/铝接头剪切强度的影响。结果表明:合金钎料的显微组织均由η(Zn)相、ε(CuZn5)相、β(ZnAl)共析相组成,混合稀土的添加使大树枝状的ε(CuZn5)相细化、分布变均匀;随着混合稀土含量的增加,合金钎料的熔点逐渐降低,润湿性能及其钎焊铜/铝接头的剪切强度均先增大后下降;当混合稀土质量分数为0.1%时,钎料在铜板和铝板上的铺展面积均达到最大,分别比未添加稀土的提高了20.4%和46.6%,其润湿铝板的界面变得连续,没有缺陷;合金钎料钎焊铜/铝接头的剪切强度也达到最大,为66.5MPa,比未添加稀土的提高了32.5%。     

Cu颗粒增强复合钎料钎焊接头的蠕变断裂及强化机理

测定不同应力和温度下Cu颗粒增强复合钎料及基体钎料钎焊接头蠕变寿命,分析Cu颗粒增强复合钎料及其基体钎料63Sn37Pb钎焊接头蠕变断裂机理。结果表明：Cu颗粒增强复合钎料钎焊接头蠕变寿命优于基体钎料。Cu颗粒表面金属间化合物形成及Cu颗粒对富Pb层阻碍作用是复合钎料钎焊接头蠕变性能改善的主要因素。钎焊接头铜基板上一薄层富Pb相的形成是蠕变裂纹产生的根源。     

CuSnNiCr真空钎焊金刚石界面微结构分析

为降低钎焊金刚石的热损伤和制造成本,采用CuSnNiCr单质金属粉作为钎料,对金刚石磨粒进行了钎焊实验。采用SEM、EDS及XRD对金刚石焊后界面微结构、钎料组织进行了分析。结果表明：适合钎焊金刚石的活性成分为Cu75Sn15Ni5Cr5,该钎料能与金刚石实现化学冶金结合,熔点适中,润湿性较好。金刚石焊后形貌完整,表面基本光滑,表面生成了连续片状（Cr,Fe）7C3。钎料凝固过程先结晶出αCu枝晶,经包晶转变和共析转变,形成了αCu枝晶、Cu5.6Sn和共析αCu,钎料的显微硬度大约为200～250HV0.2。     

锗元素对Sn-3.5Ag合金/铜界面反应的影响

通过向Sn-3.5Ag共晶合金中添加质量分数为0.1%,0.3%的锗元素,研究了锗元素对Sn-3.5Ag合金/铜界面反应的影响。结果表明:对于Sn-3.5Ag合金/铜界面,没加入锗元素时界面反应初生相为扇贝状Cu6Sn5,在热老化过程中此化合物层不断长大,且在Cu6Sn5/铜界面处生成新的Cu3Sn化合物,同时在Cu3Sn/铜界面上出现柯肯达尔空洞;当钎料中添加锗后,界面初生相也为Cu6Sn5化合物,在热老化阶段,Cu6Sn5化合物层厚度增长非常缓慢,且无Cu3Sn化合物生成,整个老化过程中都无柯肯达尔空洞出现。     

TiNi形状记忆合金与不锈钢钎焊接头的微观组织与性能

采用含Ag50％~68％、Cu10％~30％、Zn12％~20％、Sn0％~10％的银基钎料,通过激光钎焊,改变钎焊 有效热输入(激光输出功率和钎焊时间),研究了TiNi形状记忆合金与不锈钢异质钎焊接头的微观组织和性能。结 果表明:AgCuZnSn钎料对TiNi形状记忆合金和不锈钢的润湿性较好,钎焊接头界面平整、致密,与TiNi形状记 忆合金形成的界面反应层较窄,而与不锈钢形成的界面反应层较宽。钎焊有效热输入对TiNi形状记忆合金热影响 区组织和性能影响较大。钎焊有效热输入量过高,将导致TiNi形状记忆合金侧热影响区组织晶粒粗大、硬度降低、 塑性提高。严格控制钎焊工艺参数可以获得具有较高抗拉强度、形状记忆效应和超弹性的TiNi形状记忆合金与不 锈钢钎焊接头。     

晶须增强Ag-18Cu复合钎料钎焊氧化锆增韧氧化铝陶瓷接头组织试验研究

采用硼酸铝晶须增强的Ag-18Cu复合钎料对氧化锆增韧氧化铝陶瓷进行钎焊,根据钎料润湿和铺展性能的变化得出合理的晶须加入量。通过扫描电镜进行钎焊接头组织形貌观察,并通过能谱仪进行元素分析,研究钎焊接头微观结构及晶须对接头的强化机理。在改变焊接温度、焊接时间等工艺参数的情况下,进行多次钎焊试验。通过微机控制电子万能试验机及专用夹具,对钎焊后的试验件进行抗剪强度测试。通过测试得到工艺参数对钎焊接头组织及力学性能的影响规律,进而得出最优的工艺参数。     

聚晶金刚石复合片高频感应钎焊的试验研究

采用部分不等间隙接头设计方案和Ag Cu Zn Cd钎料 ,通过在空气中高频感应加热 (钎焊温度 6 90℃ ) ,成功实现了PCD复合片与 4 5钢刀杆的高强度焊接。根据钎焊试验结果 ,分析了钎料润湿性、钎焊温度、恒温保持时间和钎焊金属表面粗糙度对接头强度的影响     

添加Ni-Cr-B-Si的Cu基复合钎料真空钎焊金刚石界面微结构

为了降低钎焊金刚石的热损伤和调控钎料性能,采用添加适量Ni-Cr-B-Si的Cu基钎料对金刚石磨粒进行真空钎焊试验。采用扫描电镜、能谱仪和X射线衍射仪对金刚石焊后形貌、界面微结构、钎料组织进行了分析。结果表明：添加20%Ni-Cr-B-Si的CuSn混合粉能够与金刚石实现化学冶金结合,金刚石热损伤降低明显,焊后形貌完整,表面基本光滑,并在金刚石表面的不同晶面生成了不同类型和形貌的碳化物。钎料凝固过程中首先析出α-Cu枝晶,经过包晶转变和共析转变,形成了α-Cu枝晶、Cu5.6Sn、Cu3Sn、Ni3Sn和共析α-Cu。随着Ni-Cr-B-Si含量的增大,钎料的硬度在增大,当添加量为20%时,硬度达到360~400HV0.2。     

基于润湿识别的SMT激光软钎焊焊点质量控制研究

采用高速摄影试验方法研究表面组装激光软钎焊焊点动态形成过程及焊点红外辐射信号与焊点形成过程的关系,发现钎料的润湿过程造成红处辐射信号及其动态微分信号的突变,提出基于润湿识别的焊点质量控制方法及算法。结果表明,该控制算法能保证形成良好的激光软钎焊焊点并严格避免烧毁。根据信号的特征还可以识别出多种工艺缺陷并可进行预测控制。     

毛细管板接头真空电子束钎焊工艺

应用自制柔性化电子束钎焊系统对毛细管板接头的钎焊工艺进行了研究，探讨了钎焊工艺参数对钎料扩散深度以及钎脚高度的影响。结果表明：随着电子束输入功率或功率密度的加大，钎料向毛细管壁的扩散深度逐渐增大，钎脚高度的增长趋势显著。在一定范围内，钎料扩散深度及钎脚高度随钎料量及装配间隙的增加而增大。工件表面状态对钎脚高度的影响规律是：铰制过的试板，最有利于钎料铺展，钎脚高度最高，酸洗的试板次之，未经任何处理的试板钎脚高度最低。电子束钎焊的优化工艺参数为：加速电压60kV，束流6．5nA，加热时间37s，钎料质量25mg，聚焦电流654mA，装配间隙0．027mm。     

润湿性梯度表面上液滴运动的数值模拟

建立液滴在具有润湿梯度表面上运动的物理和数学模型,用Fluent软件模拟出液滴在润湿梯度表面上的运动过程,并从能量变化的方法得到液滴在润湿梯度表面上运动的机制.计算结果表明润湿性梯度表面上的液滴具有不同的能量状态,当液滴的接触角较大时,液滴的表面能较大,此时液滴可以自发地向低接触角的方向运动,润湿性梯度的分布状况将决定液滴运动过程的速度和加速度的大小.     

不同润滑液的电润湿性能研究

润湿性是指液体在固体表面铺展的倾向性,可以通过润湿角描述,是评价润滑液渗透性能的一个重要指标。为了研究润滑液的电润湿性,搭建电润湿润湿角测量装置,对施加负高电压的润滑液润湿角进行测量,得到不同电压下不同润滑液的润湿角变化情况,结合仿真分析施加负高压液滴润湿角变化机制。结果表明:润滑液润湿角受外加电场影响,在一定范围内,电压越大,润滑液润湿角越小;在润滑液中加入纳米颗粒可提高润滑液的电润湿性能;在同等电压下,与去离子水、去离子水基纳米流体、蓖麻油、蓖麻油基纳米流体、葵花油相比,葵花油基纳米流体的电润湿性能最好;对润滑液液滴施加电压后,液滴各位置压力场与速度场发生变化,其顶部压力场较大,速度指向液滴内部,边缘压力场较小,速度指向液滴外部,进而导致润湿角减小。     

Wetting behaviour during evaporation and condensation of water microdroplets on superhydrophobic patterned surfaces

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water repellent properties. The superhydrophobic surfaces may be generated by the use of hydrophobic coating, roughness and air pockets between solid and liquid. The geometric effects and dynamic effects, such as surface waves, can destroy the composite solid–air–liquid interface. The relationship between the water droplet size and geometric parameters governs the creation of composite interface and affects transition from solid–liquid interface to composite interface. Therefore, it is necessary to study the effect of droplets of various sizes. We have studied the effect of droplet size on contact angle by evaporation using droplets with radii ranging from about 300 to 700 μm. Experimental and theoretical studies of the wetting properties of silicon surfaces patterned with pillars of two different diameters and heights with varying pitch values are presented. We propose a criterion where the transition from Cassie and Baxter regime to Wenzel regime occurs when the droop of the droplet sinking between two asperities is larger than the depth of the cavity. The trends are explained based on the experimental data and the proposed transition criteria. An environmental scanning electron microscopy (ESEM) is used to form smaller droplets of about 20 μm radius and measure the contact angle on the patterned surfaces. The investigation has shown that ESEM provides a new approach to wetting studies on the microscale.     

THERMAL PROCESS OF VACUUM FLUXLESS LASERSOLDERING AND ANALYSIS ON SOLDER SPREADING AND WETTING

0INTRODUCTIONInordertoprotectenvironment,freonisforbiddentobeaPPliedinweldingfield.Howeveritisimpossibleforfluxremainsonjointssolderedtobecompletelycleanedinsolderingp~essforsuperfineInaterial.SOitwillerodethejointmetalandbadlyinfluencejointreliabilityofpIDducts.Recently,asfoefluenesssolderingp~esswithoutcleaningaftersolderingcanassurethejointreliability,ithasbeen.gnded[1].Atpresent,jointperformancebetweensolderandsolderedmetalsurfaceismainlystudiedinflunesssolderingmethodsbymeansofbot…     

规则粗糙固体表面液体浸润性对表观接触角影响的研究

在粗糙表面固液接触角的Wenzel模型和Cassie模型的基础上,考虑规则粗糙形貌中液体浸润性对表观接触角的影响,推导出了一种新的规则粗糙表面的表观接触角模型。数值分析结果表明,规则形貌的设计可以控制液体的浸润特性,以及固液表观接触角,其中微孔的孔深和孔分辨率等几何参数成为重要的控制参数。同时,我们进行了相关的实验验证。这种考虑液体浸润性的表观接触角模型,也提供了对表观接触角滞后现象解释的可能。     

Influence of direct electric current on wetting behavior during brazing

Frontiers of Mechanical Engineering - The wetting behavior of liquid metals is of great importance for many processes. For brazing, however, a targeted modification beyond the adjustment of...     

新型金属烤瓷材料--遮色瓷粉体的研究

用高纯长石粉等国产原料,采用熔融后水淬、湿法球磨的工艺,制备齿科用金属烤瓷材料。对自制遮色瓷粉体的粒度、润湿性能、遮色性能以及生物相容性等进行研究与测定。结果表明：自制粉体的性能已达到生物医用材料的要求,可以应用于临床。     

Thermodynamic limitations on the resolution obtainable with metal replicas

The major factor limiting resolution of metal-shadowed surfaces for electron and scanning tunnelling microscopy is the granularity of the metal film. This granularity had been believed to result from a recrystallization of the evaporated film, and hence could be limited by use of higher melting point materials for replication, or inhibited by adding carbon or other impurities to the film. However, evaporated and sputtered films of amorphous metal alloys that do not crystallize also show a granularity that decreases with increasing alloy melting point. A simple thermodynamic analysis shows that the granularity results from a dewetting of the typically low surface energy sample by the high surface energy metal film, similar to the beading up of drops of spilled mercury. The metal granularity and the resulting resolution of the metal-coated surface is proportional to the mobility of the metal on the surface after evaporation, which is related to the difference in temperature between the melting point of the metal and the sample surface temperature.     

Nanoscale Friction and Wetting on a Representative Ensemble of Model Surfaces with Different Polarities

We report experimental results of model investigations on wetting and nanoscale friction on an ensemble of substrates, involving both uniform and heterogeneous organic, and inorganic surfaces. In contrast to the external applied load-dependent friction that was found to increase linearly on all substrates, a transition was observed in the velocity-dependent frictional forces, which exclusively depends on the polarity of the contacting surfaces, no matter what their nature (organic or inorganic), chemical composition and topological organization (heterogeneity). Finally, using water contact angle data, we showed that a unique relation exists, namely a linear scaling of friction with the de-bonding (retraction) energy of the triple phase contact line that naturally connects the wetting and frictional properties on both substrates.     

超疏水表面液滴的冷凝成长特性研究

利用聚二甲基硅氧烷(PDMS)为基底采用光刻技术制备了微方柱状超疏水表面,分析了冷凝条件下超疏水表面液滴的冷凝生长特征,发现液滴的生长过程可分为微液滴成核冷凝独立生长、冷凝微液滴合并生长以及大液滴生长3个阶段。超疏水表面初始合并的液滴呈Wenzel-Cassie状态和Wenzel状态,随着冷凝液滴的成长,液滴的液-固接触面积与粗糙结构表面的表观面积之比f随着冷凝液滴尺寸的增大而增大,Wenzel-Cassie状态向完全Wenzel状态转变。最后分析了超疏水性破坏的原因。