海水中Zn（OH）2对镀锌钢腐蚀行为的影响

将镀锌钢试样浸入饱和Zn(OH)2海水溶液中以模拟腐蚀环境,采用失重法、扫描电镜(SEM)、极化曲线和交流阻抗谱研究了海水中Zn(OH)2对镀锌钢腐蚀行为的影响。结果表明:电极表面上由于腐蚀产物Zn(OH)2的吸附,镀锌层的膜结构遭到破坏,随着浸泡时间的延长,镀锌钢表面发生腐蚀反应时的电荷转移电阻逐渐减小,自腐蚀电流密度逐渐增大,腐蚀产物Zn(OH)2的吸附诱导了镀锌层表面点蚀的发生。     

电阻点焊电极的研究进展与发展趋势

电极是电阻点焊工作过程中最关键的部件,电极性能的优劣直接影响点焊的焊接质量和焊接效率.介绍了点焊电极的失效形式和失效机理,分别论述了点焊电极成分、强化工艺和结构设计以及点焊工艺和被焊件材料对电极性能的影响,提出了改善点焊电极寿命的未来研究发展趋势.     

电火花沉积工艺对点焊电极TiC沉积层硬度的影响

为了改善镀锌钢板点焊电极的寿命,在电极表面进行了电火花振动熔敷TiC的工艺试验。通过正交试验考察了沉积工艺参数（电容、基体电极转速、振动频率、沉积时间）对沉积层硬度的影响,并考察了对基体材料进行前、后处理对沉积层硬度的影响。结果表明,电容是影响电火花沉积层硬度的主要因素;振动频率、基体转速、沉积时间对沉积层硬度影响较小。试验条件下最佳的工艺参数为：电容量30000μF,基体转速1320Hz,振动频率A档,沉积时间120s。前处理改善界面,对沉积层硬度影响小;后处理促进元素扩散,降低沉积层硬度,但减少了过渡层的微孔和微裂纹。     

热镀锌层对Q235钢在模拟混凝土碱性环境中的保护作用

为了探知DN25热镀锌钢管热镀锌层对Q235管材的保护作用,对比测量了不同模拟混凝土介质中Q235钢热镀锌前后的电极电位和两者间的电偶电流,从热力学和动力学方面判断镀锌层对Q235钢的保护作用。结果表明:在NaCl中性溶液及pH=10.0～13.0 Ca(OH)2溶液中,热镀锌层对Q235钢均有牺牲阳极的保护作用;在含Cl-模拟混凝土饱和Ca(OH)2碱性溶液[Ca(OH)2+NaCl,pH值为12.5]中,镀锌后的电极电位和电偶电流均波动较大,其电极电位比镀锌前的负,大部分时间内镀锌后流过的是阳极电流,某些瞬间镀锌前后间的电偶电流会发生逆转。     

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。     

Zn~(2+)离子掺杂对纳米TiO_2薄膜电极表面形貌和紫外光电性能的影响

采用sol-gel法制备了Zn2+离子掺杂的锐钛矿相纳米TiO2薄膜电极。通过X射线衍射(XRD)、吸收光谱、原子力显微镜(AFM),结合光电流作用谱研究了Zn2+离子掺杂对TiO2薄膜电极表面形貌和紫外光电性能的影响。结果表明,在所选浓度范围内,Zn2+离子掺杂浓度对薄膜的相组成和紫外光吸收强度无明显作用,但可显著改变薄膜表面颗粒大小和形貌特征,从而影响电极光电性能。0.1%(摩尔分数)Zn2+离子的掺杂使膜内颗粒尺寸由30nm增大至40nm,同时使表面颗粒的生长具有一定的择优取向,颗粒形状由本征薄膜的类球形变为垂直于膜面的柱状颗粒。这一结构大幅增大了薄膜的表面积,提高了载流子在固-液界面的传输效率,促使电极光电流密度(PCD)比本征电极提高40%。随掺杂浓度的提高,表面颗粒尺寸逐渐增大,形状恢复为类球形,电极光电性能有所降低。当掺杂浓度达到5%(摩尔分数)时,颗粒粒径急剧增大至130nm,表面颗粒因熔点降低而熔合成无孔表面,导致电极PCD急剧降低。     

Mg2Ni纳米储氢合金结构及电化学性能研究

利用高能球磨方法制备纳米Mg2Ni储氢合金,用于高容量MH／Ni电池氢化物电极电化学性能研究。XRD和TEM测试结果表明,机械合金化方法制备Mg2Ni合金的历程为合金化——非晶化——纳米晶化,球磨时间直接影响Mg2Ni合金的结构。高能球磨20h可以制备非晶态Mg2Ni合金,比普通的机械合金化方法制备非晶态Mg2Ni合金的时间减少了约5倍之多;高能球磨30h可以制备纳米晶态Mg2Ni合金,粒径在10nm以下,有团聚现象。研究了Mg2Ni纳米氢化物电极在不同温度下的电化学性能,并从热力学角度就Mg2Ni纳米氢化物电极的某些高温电化学性能进行了解释和推测。实验结果表明：在30～70℃范围内,随着温度增加,氢化物电极的电化学容量逐渐增加,在70℃时电化学容量可达530．5mAh／g,约为30℃放电容量273．2mAh／g的2倍,Mg2Ni纳米氢化物电极具有较好的高倍率放电性能及大电流充放电性能,这表明机械合金化方法制备的Mg2Ni纳米氢化物电极具备电动车用大型MH／Ni电池负极材料的初步条件,但容量衰减严重。     

锌-铁合金异常共沉积中锌沉积机理的研究(Ⅱ)——Zn(OH)_4~(2-)阴极放电的交流阻抗研究

根据拟定的电极反应机理对Zn(OH) 2 -4阴极沉积的交流阻抗进行了理论研究及试验测试。结果表明 :第一个得电子反应为速度控制步骤 ;电极反应过程中存在有电活性的吸附态中间产物 ,而且吸附态的中间产物是以电感的形式影响电极反应的阻抗 ;拟定的机理正确。因此 ,Zn Fe合金异常共沉积中Zn的阴极沉积机理可确定为 :Zn(OH) 2 -4=Zn(OH) 2 +2OH-;Zn(OH) 2 +eZn(OH) ad+OH-(rds) ;Zn(OH) ad+e=Zn +OH-。其中 ,Zn(OH) 2 -4阴极放电的交流阻抗例证表明 ,第二步为电极反应速度控制步骤。     

TiB2含量及T6热处理对原位TiB2/ZL111复合材料显微组织和硬度的影响

采用原位合成法制备了TiB_2/ZL111复合材料,并对铸态及T6态TiB_2/ZL111复合材料的显微组织及硬度进行了研究。结果表明:显微组织方面,铸态TiB_2/ZL111复合材料主要由α-Al、共晶Si和TiB_2组成,TiB_2颗粒平均尺寸为1μm,呈六边形或卵圆形分布于α-Al晶界处;TiB_2有效细化了ZL111的α-Al晶粒,使长条状共晶Si向等轴状转变;T6热处理使共晶Si进一步演变为近球状,并有效改善了TiB_2的团聚现象。硬度方面,TiB_2含量越高,铸态TiB_2/ZL111复合材料的硬度越高,铸态10%TiB_2/ZL111(质量分数)复合材料的维氏硬度(120.13Hv)比铸态ZL111合金(96.63Hv)提高了24.32%;T6热处理使ZL111合金及TiB_2/ZL111复合材料的硬度进一步提高,但硬度提高率随TiB_2含量的增大而减小,TiB_2消弱了T6热处理的时效硬化作用,归因于TiB_2颗粒抑制了Al_2Cu相的析出。     

锌-铁合金异常共沉积中锌沉积机理的研究(Ⅱ)--Zn(OH)2-4阴极放电的交流阻抗研究

根据拟定的电极反应机理对Zn(OH)2-4阴极沉积的交流阻抗进行了理论研究及试验测试.结果表明:第一个得电子反应为速度控制步骤;电极反应过程中存在有电活性的吸附态中间产物,而且吸附态的中间产物是以电感的形式影响电极反应的阻抗;拟定的机理正确.因此,Zn-Fe合金异常共沉积中Zn的阴极沉积机理可确定为:Zn(OH)2-4=Zn(OH)2 2OH-;Zn(OH)2 e→Zn(OH)ad OH-(rds);Zn(OH)ad e=Zn OH-.其中,Zn(OH)2-4阴极放电的交流阻抗例证表明,第二步为电极反应速度控制步骤.     

镀锌钢板蒸镀镁层的耐腐蚀机理

采用真空蒸镀技术在镀锌钢板上蒸镀镁,制得了蒸镀镁层,将其在5%NaCl溶液中浸泡,运用XRD,SEM和电化学方法等对其腐蚀产物进行了分析.对2种材料的的腐蚀行为进行了研究,探讨了其耐腐蚀机理.结果表明:镀锌钢板蒸镀镁层是以MgZn2和Mg2Zn11.金属间化合物的形式存在;其腐蚀产物是以致密且具有良好绝缘性的ZnCl2·4Zn(OH)2·H2O和致密的Zn4CO3(OH)6·H2O为主体,而纯锌镀层的腐蚀产物是以疏松且具有N型半导体性质的ZnO为主体;蒸镀镁层的形成可以抑制Zn(OH)2向ZnO的转化,能促进Zn(OH)2向ZnCl2·4Zn(OH)2·H2O和Zn4CO3(OH)6·H2O的转化,后二者能够牢固地覆盖在基体表面,从而延缓了锌的腐蚀进程;在宏观上表现为镀锌钢板蒸镀镁层腐蚀产物相对于纯锌镀层更加致密,在电化学行为上表现为镀锌钢板蒸镀镬层具有更小的腐蚀电流和更高的极化电阻.     

Dissimilar joining of galvanized high-strength steel to aluminum alloy in a zero-gap lap joint configuration by two-pass laser welding

A welding procedure based on using two-pass laser scans is introduced for dissimilar joining of overlapped galvanized high-strength dual-phase (DP) steel DP590 to aluminum alloy (AA) 6061 sheets. The first pass is based on a defocused laser spot that scans across the top of the two overlapped sheets and heats the zinc coating at the faying surface to be melted and partially vaporized, while the second pass is executed with a focused laser spot in order to perform the welding. Completely defect-free galvanized steel to aluminum lap joints were obtained by using this two-pass laser welding procedure. An on-line machine vision system was applied to monitor the keyhole dynamics during the laser welding process. An energy-dispersive X-ray spectroscopy (EDS) was carried out to determine the atomic percent of zinc, aluminum, and iron in the galvanized steel to aluminum lap joints. Mechanical testing and micro-hardness test were conducted to evaluate the mechanical properties of the galvanized steel to aluminum lap joints. The experimental results showed that the lap joint of galvanized steel to aluminum obtained by the two-pass laser welding approach had a higher failure value than those joints obtained when the zinc at the faying surface was mechanically removed under the same welding speed and laser power.     

Microstructure and failure behavior of dissimilar resistance spot welds between low carbon galvanized and austenitic stainless steels

Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode.     

Effect of deep cryogenic treatment on electrode life and microstructure for spot welding hot dip galvanized steel

In this article, the deep cryogenic treatment technology is first applied in the treatment of electrodes, for spot welding hot dip galvanized steel plate and electrode, life experiment is carried out. The microstructure and elements distribution of the deep cryogenic treatment electrodes, and non-cryogenic treatment of electrodes for spot welding hot dip galvanized steel is observed by, scanning electrical microscope and X-ray diffraction. The experimental results shows that deep cryogenic treatment makes Cr, Zr, in deep cryogenic treatment of electrodes, emanate disperseadly and makes the grain of deep cryogenic treatment of electrodes, smaller than non-cryogenic treatment ones, so that the electrical conductivity and the thermal conductivity of deep cryogenic treatment electrodes are improved very much, which makes electrode life for spot welding hot dip galvanized steel that improves obviously.     

镀层厚度对热镀锌热轧板耐蚀性的影响

为模拟热镀锌板的实际使用情况,以剪裁后不同镀层厚度的热镀锌热轧板为研究对象,采用光学显微镜(OM)观察镀锌前后基体组织,通过中性盐雾试验分析镀层厚度对热镀锌热轧板产生白锈和红锈的影响规律。结果表明:在腐蚀过程中,腐蚀沿镀层由四周向内部扩展,同时由钢基体向表面扩展和锌层表面向内部扩展;随着镀层厚度增加,腐蚀扩展时间增长导致腐蚀时间增长,热镀锌板抗白锈能力增强,意味着耐蚀寿命增加;但抗白锈能力与镀层厚度呈非线性关系,涂层较厚时,通过增加镀层厚度提高热镀锌板抗白锈能力的效率降低。     

A novel Ti cored wire developed for wire-feed arc deposition of TiB/Ti composite coating

A novel Ti cored wire containing TiB2,Al60V40 and Ti6Al4V mixed powders was developed for wire-feed arc deposition of TiB/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed TiB2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of TiB whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of TiB whisker to some extent.The decomposition process of TiB2 particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV0.5)as compared with Ti6Al4V substrate(326 HV0.5).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of TiB whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.     

不锈钢焊条熔滴过渡形态与交流稳弧性的关系

采用水中收集熔滴、平堆板焊、高速摄影等试验方法，研究了不锈钢焊条熔滴过渡形态与交流稳弧性的关系。结果表明：细熔滴过渡时交流稳弧性好，电极斑点面积增大是改善交流稳弧性的主要原因；促使熔滴细化的药皮组成物、适当的药皮厚度、合理的焊条烘干温度和合适的焊接电流，对改善交流稳弧性都具有重要作用。     

Influence of fusion zone size and failure mode on mechanical performance of dissimilar resistance spot welds of AISI 1008 low carbon steel and DP600 advanced high strength steel

The work here addresses the investigation of the effect of the welding parameters (welding time, welding current and electrode force) on the overload failure mode and mechanical performance of dissimilar resistance spot welds between drawing quality special killed AISI 1008 low carbon steel and DP600 dual phase steel. Mechanical properties of spot welds are described in terms of failure mode, peak load and energy absorption during the quasi-static tensile-shear test. Three distinct failure modes were observed during the tensile-shear test: interfacial, pullout and partial thickness–partial pullout failure modes. Correlations among failure mode, welding parameters, weld physical attributes and weld mechanical performance are analyzed. Effect of expulsion on mechanical performance of welds is also investigated.     

镀锌板焊接件磷化工艺研究

针对目前焊接件焊缝区磷化效果不理想的情况,对镀锌板焊接件进行了3种不同工艺的磷化。通过扫描电镜观察磷化表面的形貌,采用硫酸铜滴定试验评价磷化膜的耐蚀性。研究表明:镀锌板焊接件用同一种磷化工艺很难达到预期效果;而先对焊缝用硝酸锌调节的磷化液喷淋磷化2 min,然后在Zn O调节酸度的磷化液中浸泡磷化2 min,焊缝和母材都可得到均匀、细小、致密的磷化膜,耐蚀性均较好。     

镀锌钢的液态金属脆现象及其在电阻点焊过程中的表现

液态金属脆是指通常具有韧性的固体金属或者合金与液态金属直接接触且受到拉伸应力时,其塑性降低并发生脆性断裂的现象。钢在液态锌中会发生液态金属脆现象,这在镀锌钢的热拉伸实验中得到了证实。此外,研究人员发现在镀锌高强钢的电阻点焊过程中也会出现液态金属脆现象,表现为在焊点表面出现大量裂纹,这些裂纹对焊点性能存在潜在危害。本文回顾了镀锌钢液态金属脆现象的热拉伸实验研究,阐明了影响脆化现象的实验因素;综述了镀锌钢在电阻点焊过程中发生液态金属脆现象的研究进展,分析了产生裂纹的位置及其影响因素,并总结了可能的解决方案。