电弧作用下AlSi5钎料在镀锌钢板上铺展及界面行为研究

采用 TIG 电弧钎焊试验方法,主要研究了电流大小、电弧加热时间以及弧长对 AlSi5钎料在镀锌钢板上润湿铺展及界面行为的影响。实验结果表明：随着电流、燃弧时间和某一范围内弧长的增加,钎料在镀锌钢板上的润湿角逐渐减小,铺展面积逐渐增加,并在某一特定范围时润湿铺展性能达到最佳;随着燃弧电流的增加,界面金属间化合物的厚度呈现先增加后减小的趋势,靠近母材一侧有 Fe2 Al5相生成,钎料一侧则生成 FeAl3相;Al 元素扩散到界面处与 Fe 元素发生扩散反应形成 Fe-Al 金属化合物颗粒,在钎缝中弥散分布着 Si 元素,对钎缝有强化作用。     

6061铝合金分别在Q235钢和纯钛表面的反应润湿

采用座滴法在高真空条件下研究了熔融6061铝合金在600~700℃分别与Q235钢和纯钛的润湿行为。研究表明两者都为典型的反应润湿,且最终润湿性随着温度的升高而改善;界面反应的自由能变化对最终润湿性及界面结构影响较小,而基板金属在铝中的溶解度不同决定了界面反应层厚度(即溶解度越大则反应层越厚);三相线附近的还原反应诱发了前驱膜的产生,且最终润湿性越好则前驱膜越宽;两者体系的铺展动力学均可以由RPC模型描述:在Al/Ti体系中整个润湿过程分为两个阶段,即先非线性铺展,后线性铺展阶段,两个阶段的铺展活化能分别为72kJ/mol、118kJ/mol,且界面上存在Si的富集;在Al/Q235钢体系中整个润湿过程呈线性铺展,铺展活化能为86kJ/mol,无Si元素在界面富集。     

典型接地材料在陕北黄土高原土壤模拟液中的短期腐蚀行为

目前,有关陕北黄土高原土壤对典型接地材料的腐蚀研究鲜有报道。采用浸泡试验、EIS测试和表面分析方法,研究了Q235碳钢、镀锌钢、镀铜钢、紫铜和304不锈钢在陕北黄土高原土壤模拟液中的腐蚀行为。结果表明:5种典型接地材料在其土壤模拟液中的耐蚀性大小顺序为304不锈钢紫铜镀铜钢镀锌钢Q235碳钢;Q235碳钢的腐蚀产物具有明显的层状结构,腐蚀产物内层紧密,对基体有较好的保护作用,外层疏松,氧化充分;镀锌钢、镀铜钢和紫铜的表面腐蚀产物分别主要为锌和铜的氧化物;304不锈钢的表面未见明显的腐蚀产物。     

陕西土壤模拟液中3种典型接地金属材料的腐蚀行为

为了弄清3种典型接地金属材料(H62黄铜、Q235钢、镀锌钢)在陕西土壤中的腐蚀情况,采用失重法(外加电流浸泡)、电化学测试、扫描电镜(SEM)和X射线衍射(XRD)研究了其在陕西中部土壤模拟液中的腐蚀行为和电化学规律。结果表明:在有外加电流的模拟液中浸泡,随浸泡时间延长,Q235钢腐蚀速率逐渐变慢,镀锌钢表面镀锌层腐蚀较快,H62黄铜的腐蚀速率变化不大;Q235钢、镀锌钢、H62黄铜的腐蚀产物分别主要为α-FeOOH、β-FeOOH、Fe3O4,ZnO、Zn(OH)2、FeOOH、Zn5(CO3)2(OH)6和Cu2O、CuO、CuCl2;在含相同NaCl浓度的模拟液中,H62黄铜的耐腐蚀性能最好,镀锌钢的次之,Q235钢的最差。     

金属/陶瓷润湿性的实验表征和理论预测研究进展

金属/陶瓷体系的润湿性研究在金属与陶瓷的连接、金属液的熔炼和提纯、浸渗法和液相法制备复合材料等领域都有着重要意义。金属熔体在陶瓷表面的润湿过程中,会出现基板在熔体中溶解、界面吸附和互相反应等,是一种较为复杂的物理化学现象。有关金属/陶瓷润湿性的实验和理论研究一直是国际上材料学领域的热点之一。目前金属/陶瓷润湿性主要通过测量接触角θ(借助Young's方程计算)来得出,润湿性表征方法存在较大局限性,特别是接触角对实验条件高度敏感,其往往难以准确反映润湿性,以及适用于高熔点合金与陶瓷体系的方法较为缺乏。因此,除对接触角测试方法进行改进外,很多研究者也试图通过理论计算来考察润湿性,但至今尚未发展出能够很好地应用于所有金属/陶瓷体系的理论预测模型。润湿性实验表征方法的近期研究主要集中在改良座滴法、滴定法、毛细上升法和感应熔化法等。其中,改良座滴法相比传统座滴法能够消除熔体表面氧化膜的影响。感应熔化法可以使高熔点合金(如Ti合金等)熔化,具有独特优势(相比之下其他几种方法只适用于Al系、Mg系等低熔点合金与陶瓷的体系)。在理论预测模型方面,除直接基于Young's方程,根据表面张力模型来研究润湿性外,也有学者尝试结合YoungDupré方程,从热力学和原子键的角度揭示反应界面润湿性的内在规律。同时,将润湿视为一种反应现象,对界面反应吉布斯自由能变化和润湿过程中表面相的能量变化加以考虑,也形成了一种新的定性衡量润湿性的标准。此外,研究者还在润湿铺展动力学方面取得了一些重要成果,包括直接根据金属形核理论来计算润湿角,以及利用如流体动力学模型、分子动力学模型、反应控制模型和扩散控制模型等来预测金属/陶瓷体系的润湿速率。本文主要从润湿过程的机制、接触角的测试方法和用以预测润湿性的理论模型三个方面,综述了金属/陶瓷润湿性领域的实验和理论研究进展。     

抗压容器钢在模拟工业码头大气环境下的腐蚀行为研究

为探究抗压容器钢在模拟工业码头大气环境下的腐蚀行为,利用失重分析、EDS、XRD和电化学方法研究了不同模拟加速试验周期下抗压容器钢Q235和16MnNiVR钢的腐蚀行为。结果表明：抗压容器钢Q235和16MnNiVR钢在模拟工业海洋大气环境试验中,其腐蚀速率先呈现上升趋势,随着锈层由疏松逐渐变致密,腐蚀速率会发生不同程度地下降。在此加速试验下2种钢的腐蚀产物化学性质一致,所发生的腐蚀行为差异是由金属基材表面腐蚀产物致密性所致,在东南沿海工业海洋大气环境腐蚀因子作用下,16MnNiVR钢的耐蚀性可达到Q235钢的1.6倍。     

镀锌钢板与6061铝合金搭接搅拌摩擦钎焊

目的 分析Q235镀锌钢与6061铝合金搅拌摩擦钎焊接头在不同旋转速度下的组织性能。方法 使用0.3 mm的Zn作为中间层,通过搅拌摩擦钎焊,焊接6061铝合金与Q235镀锌钢,观察测试其接头组织和力学性能。结果 转速从660 r/min增加到1750 r/min时,随着进入到6061铝合金近缝区Zn元素的增加,铝合金搅拌区孔洞变小。界面Zn过渡层变薄。在适中的转速下,界面结合良好。接头最大平均拉剪力先增加后降低,界面显微硬度升高,硬度梯度增加。结论 搅拌头在1320 r/min转速下,测得搅拌摩擦钎焊接头平均拉剪力为2.33 kN。     

钢板锌镁镀层制备及退火工艺对锌镁合金化的影响

钢板表面的锌镁合金镀层可以提高其耐腐蚀性能,而锌镁金属间化合物MgZn2和Mg2Zn11的形成可能是耐腐蚀性能提高的主要因素。本文在镀锌钢板表面采用真空热蒸发镀镁,并由快速退火工艺形成锌镁合金镀层,进而研究退火条件对形成锌镁合金镀层的影响,即通过改变退火温度和时间,得到不同的合金成分,然后通过X射线衍射分析退火条件对合金成分的影响。研究表明,退火温度较低时,不会形成锌镁合金;退火温度越高,形成的锌镁合金相越多,合金化程度越高;退火温度过高会导致铁锌合金相生成。退火时间对合金化也有类似规律。     

金属镀层对铝/钢激光熔钎焊接头组织与性能的影响

针对在铝/钢焊接过程中,钢的表面金属镀层对铝/钢激光熔钎焊接头性能有着重要影响的问题,研究铝合金在不同金属镀层的低碳钢表面的铺展效果,通过SEM对不同金属镀层下熔钎焊接头界面微观组织形态、金属间化合物厚度、种类等进行分析,并进一步研究不同金属镀层下铝/钢接头的力学性能及断口形貌。结果表明:钢表面的金属镀层对铝/钢激光熔钎焊过程中5A06铝合金在钢上的铺展与浸润有着较大的影响,其中5A06铝合金在镀铝钢上的铺展效果最佳,且铝合金与镀铝锌钢熔钎焊的接头抗拉性能最好,达到母材铝合金的70%。铝/钢界面金属间化合物主要由铝铁金属间化合物组成,其中在镀铝钢、镀铝锌钢、镀锌钢中主要存在Fe2Al5,FeAl3,FeAl等金属间化合物,在镀镍钢界面中还存在Fe4Al13等金属间化合物。     

Si、Sn、Mg对Q235钢在铝浴中腐蚀行为的影响

为降低钢在铝液中的腐蚀,通过对比纯铝、Al-Si、Al-Sn、Al-Mg铝合金熔体静态腐蚀作用下Q235钢/熔体界面的结构、形貌和腐蚀速率,研究了Si、Sn、Mg元素对Q235在铝合金熔体中静态腐蚀的影响。结果表明:Q235在不同铝合金熔体中均发生腐蚀,表面均形成Fe_2Al_5金属间化合物层,在铝液中添加Si可以使形成的Fe_2Al_5层由舌状转变为平板状,减小Fe_2Al_5层厚度,并显著减缓腐蚀速率;添加Sn和Mg不改变Fe_2Al_5层的形态和厚度,减缓腐蚀速率效果不如Si显著;Si、Sn、Mg不改变Fe_2Al_5择优生长的特点;Si降低腐蚀速率的机制是阻塞Fe_2Al_5空位孔道抑制原子扩散;Sn、Mg降低腐蚀速率的机制是占位阻隔减缓扩散速率。     

Q235钢、Cu-Cr合金铸铁和TP304H不锈钢在熔融Zn-5%Al-RE合金中的耐蚀性研究

为研究铁基材料的成分和显微组织对其耐熔蚀性能的影响,将Q235钢、Cu-Cr合金灰铸铁、TP304H不锈钢及喷丸的TP304H试样在熔融Zn-5%Al-RE合金中进行了熔蚀试验(试验温度为470℃),并进行了熔蚀速率测定和截面形貌观察(SEM)。结果表明:在试验条件下,Q235钢在熔融合金中不能形成连续致密的Al-Fe金属间化合物层;Cu-Cr合金铸铁中的石墨及珠光体对Al、Fe原子扩散起到了阻挡作用;TP304H不锈钢由于奥氏体结构的致密性,Al原子在其中的扩散速率低,同时在Al-Fe化合物层之外形成了Zn-Al-Cr-RE相,对化合物层起到一定的保护作用;TP304H不锈钢经喷丸处理后由于生成马氏体,使Al原子扩散速率提高,熔蚀速率增大。4种试验材料在熔融Zn-5%Al-RE中的耐蚀性能从高到低的排序:TP304H喷丸处理的TP304HCu-Cr合金铸铁Q235钢。     

Effects of copper addition on microstructure and strength of the hybrid laser-TIG welded joints between magnesium alloy and mild steel

Lap joint of magnesium alloy AZ31B to mild steel Q235 with the addition of copper interlayer by hybrid laser-TIG welding technique was investigated. The microstructure, element distribution at interfaces, and intermediate phases of joints were examined by scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA), and X-ray diffraction (XRD), respectively. The results showed that intermetallic compounds Mg₂Cu with rod-like structure in the joint and equiaxed structure at interface were found, and the bonding between copper and steel was realized by mixing of copper and steel at upper margins of molten pool and a little solid solution of copper in iron at the bottom and side of molten pool. Besides, comparing with that without any interlayer, the wettability of molten magnesium alloy on steel was enhanced, which led to an intimate connection. In the end, the joining mechanism of magnesium–steel joints with copper interlayer was discussed.     

Investigation of laser welding on butt joints of Al/steel dissimilar materials

Dissimilar metals of AA6013 aluminum alloy and Q235 low-carbon steel of 2.5 mm thickness were butt joined using a 10 kW fiber laser welding system with ER4043 filler metal. The study indicates that it is feasible to join aluminum alloy to steel by butt joints when zinc layer was hot-dip galvanized at the steel’s groove face in advance, and better weld appearance can be obtained at appropriate welding parameters. The joints had dual characteristics of a welding joint on the aluminum side and a brazing joint on the steel side. The smooth Fe₂Al₅ layer adjacent to the steel matrix and the serrated-shape FeAl₃ layer close to the weld metal were formed at the brazing interface. The overall thickness of Fe–Al intermetallic compounds layers produced in this experiment were varied from 1.8 μm to 6.2 μm at various welding parameters with laser power of 2.85–3.05 kW and wire feed speed of 5–7 m/min. The Al/steel butt joints were failed at the brazing interface during the tensile test and reached the maximum tensile strength of 120 MPa.     

Microstructural characteristics of lap joint between magnesium alloy and mild steel with and without the addition of Sn element

Lap joint of AZ31B Mg alloy to Q235 steel by hybrid laser-TIG welding was studied. Microstructures of Sn-free and Sn-added joint were investigated, and the intermediate phase of Sn-added joints was also inspected. In contrast with the Sn-free joints, intermetallic compound Mg₂Sn with dendritic structure distributed in the grain boundaries of Mg alloy was identified; Gaps at the interfaces were vanished as the wettability of Mg alloy with the addition of Sn on steel was improved. Big particles in fusion zone became even smaller or disappeared in the Sn-added joints.     

Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel

Dissimilar metals TIG welding-brazing of aluminum alloy to galvanized steel was investigated, and the wettability and spreadability of aluminum filler metal on the steel surface were analyzed. The resultant joint was characterized in order to determine the brittle intermetallic compound (IMC) in the interfacial layer, and the mechanical property of the joint was tested. The results show that the zinc coated layer can improve the wettability and spreadability of liquid aluminum filler metal on the surface of the steel, and the wetting angle can reach less than 20°. The lap joint has a dual characteristic and can be divided into a welding part on the aluminum side and a brazing part on the steel side. The interfacial IMC layer in the steel side is about 9.0 μm in thickness, which transfers from (α-Al + FeAl₃) in the welded seam side to (Fe₂Al₅+ FeAl₂) and (FeAl₂+ FeAl) in the steel side. The crystal grain of the welded seam is obviously larger in size in the aluminum side. The local incomplete brazing is found at the root of the lap joint, which weakens the property of the joint. The fracture of the joint occurs at the root and the average tensile strength reaches 90 MPa.     

Research on explosive welding of aluminum alloy to steel with dovetail grooves

In order to explore a new method for the explosive welding of aluminum alloy to steel, a 5083 aluminum alloy plate and a Q345 steel plate with dovetail grooves were respectively employed as the flyer and base plates. The parameters adopted in the explosive welding experiment were close to the lower limit of weldable window of 5083 aluminum alloy to Q345 steel. The bonding properties of 5083/Q345 clad plate were studied through mechanical performance tests and microstructure observations. The results showed that the aluminum alloy and steel plates were welded under the actions of metallurgical bonding and meshing of dovetail grooves. The tensile shear strength of 5083/Q345 clad plate met the requirements of the bonding strength of Al/Fe clad plate. The interfaces between aluminum alloy and the upper and lower surfaces of dovetail grooves were mainly welded through direct bonding, and discontinuous molten zone emerged in the local region; while the interface between aluminum alloy and the inclined surface of dovetail grooves was bonded by continuous molten layer. The brittle intermetallic compounds FeAl₂ and Al₅Fe₂ were generated at the bonding interfaces of 5083/Q345 clad plate. The fracture surface of the tensile specimen exhibited ductile and quasi-cleavage fractures.     

Arc deposited AlSi12 cladding layer on steel plate without zinc coating

ABSTRACT

AlSi12 cladding layer was fabricated on steel plate without zinc coating via cold metal transfer arc deposited technique. The wettability, morphologies, microstructures, and mechanical properties of the cladding layer were investigated. The cladding layer exhibited favourable wettability with steel plate. Large swing amplitude and high swing frequency were the key factors to achieve excellent wettability. The cladding layer was composed of primary Al dendrites and (Al?+?Si) eutectic structure, and the microstructures were refined. Continuous and thin intermetallic compound layer appeared at AlSi12/steel interface, and reliable bonding strength between the cladding layer and steel plate was achieved. The fracture surface exhibited both brittle fracture and ductile fracture.