Composition and Morphology of Zn-Co Alloy Coatings Deposited by Means of Pulse Plating Containing Reverse Current

The influence of bath constituents and pulse parameters on cobalt content, surface morphologies and grain size of Zn-Co alloy deposits was studied using a pulse plating technique with a square- wave current containing reverse pulse, It is found that Zn-Co alloy coatings obtained from the bath with the cobalt ion concentration over 60 wt% have a higher cobalt content in deposits. The results of pulse plating show that the average current density and reverse anodic current density amongst the variables investigated have very strong effects on the cobalt content in the Zn-Co alloy deposits. It is possible to electrodeposit Zn-Co alloy coatings with 10-90 wt% cobalt by modulating pulse parameters. The grain size, surface appearance and internal stress in the deposit were improved significantly by introducing the reverse current.     

Interface conjunction factors of thermal barrier coatings and the relationship between factors and composition

1 Structure and composition of thermal barrier coatings The thermal barrier coatings (TBCs), having superior properties of heat resistance, corrosion resistance, wear resistances and low heat conductivity, are mainly used in the aeronautic turbines with large thrust force-weight ratio. In TBCs ceramics is covered on the metal matrix in the form of coatings to withstand high service temperature [1]. Today most of the TBCs have the dou-ble-layer- structure of alloy matrix + the bonding laye…     

Electrochemical behavior of Mg-Al-Pb alloy in 3.5% NaCl solution

An investigation on electrochemical behavior of Mg-5%Pb alloy, Mg-6%Al alloy and Mg-6%Al-5%Pb alloy(mass fraction) in 3.5% Na Cl(mass fraction) solution was conducted using electrochemical measurements and corroded morphology observation, in which solid solution and the as-aged state of each alloy were compared to discuss the influence mechanism of lead and aluminium on the electrochemical properties of alloys. The X-ray diffraction(XRD) analysis was performed to make microstructure characterization. The electrochemical results indicate that the corrosion of Mg-5%Pb alloy is predominated by homogeneous pitting and dissolution of PbCl_2 film due to Cl ions attack, while corrosion crevice propagates along grain boundaries in solid solution of Mg-6%Al alloy and the micro galvanic corrosion also plays vital role in Mg_(17)Al_(12) phase containing experimental alloys. The co-existence of lead and aluminium in magnesium alloy increases corrosion current density and electrochemical activity as well. The comparison between solid solution and the as-aged state demonstrates that Mg_2 Pb and Mg_(17)Al_(12) somewhat increase corrosion resistance but lighten anodic polarization by facilitating corrosion product flaking off.     

Electrodeposition of Ni-Cr alloy on aluminum substrate

1 INTRODUCTIONOwing to low mass , high strength and easymachining, aluminum ( Al) and its alloys havebeen widely appliedin many fields .But the chemi-cal character of Al is very active ,it can be oxidizedeasilyinthe at mosphere and erodedinthe foul con-dition,and its wear resistance is poor . All theseseriously affect its application andlifeti me .It is aneffective protective measure to i mprove perform-ance by means of plating alloy on Al substrate .Ni-Cr alloys have many characteristi…     

新型Fe-Mn-Al-Cr合金的组织及耐酸性能的研究

设计了几种不同铬质量分数和铝质量分数的Fe-Mn-Al-Cr合金,将以前设计的Fe-25．65Mn-4．1Al-4．13cr和1Cr18Ni9Ti作为对比试样．金相观察结果表明：当锰质量分数降到15％时合金仍能呈单相奥氏体,但当铬铝达到一定值时出现铁素体．应用阳极极化技术和失重法研究了各种合金在0．5mol／L H2SO4和1 mol／L HNO3中的耐腐蚀性能,结果表明：随铬质量分数的增加,合金的耐酸性能先提高后降低;随铝质量分数的增加,合金的耐酸性能下降．铝在硝酸中大大提高了合金的耐腐蚀性,而在硫酸中作用不大;降低锰铝并适当升高铬质量分数既可得到更好耐酸性能的合金又降低了成本,经钝化后的Fe-Mn-Al-Cr合金的耐硝酸性能比1Cr18Ni9Ti好．     

Electroless Ni-P deposition on magnesium alloy from a sulfate bath

A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.     

变质Al-xMg2Si合金中超细初生Mg2Si的制备

在未变质Al-xMg₂Si合金中,随着Mg\Si含量从18降低到14 wt.%,初生Mg₂Si晶粒尺寸发生明显细化,由~30 mm减小到~10 mm;当合金中Mg\Si的含量降低到12 wt.%,初生Mg₂Si全消失,其金相组织为单一共晶相组成。对Al-xMg₂Si进行0.5 wt.% Ca-Sb复合变质处理,当合金中Mg\Si的含量降低到10 wt.%,合金中金相组织为初生α-Al+共晶Mg₂Si组成。在0.5 wt.% Ca-Sb复合变质的Al-xMg₂Si合金中,由于变质剂的作用,在Al-xMg₂Si合金中,树枝晶状初生Mg₂Si消失,转变为细小的多边形,随着合金中Mg\Si含量从18降低到12 wt.%,初生Mg₂Si晶粒尺寸从~15 mm降低到~5 mm,形成超细初生Mg2Si晶体。对合金进行力学性能测试发现,超细初生Mg2Si的形成对提高合金强度、硬度作用较大。     

焊接铝合金柱承载力研究

铝合金作为一种新型结构材料,在现代建筑中得到了越来越广泛的应用。国内目前关于挤压型材已经进行了大量研究[1],但有关焊接铝合金构件的研究很少。由于铝合金焊接后受焊接热影响较大,试件中除了产生残余应力,在焊缝附近的局部区域材料强度还将大大降低,该区域被称为热影响区(HAZ)。而对于钢结构,由于其热导率比铝材小得多[2],因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区的宽度也比铝合金小得多。这将使得铝合金受压杆件的承载力研究变得更为复杂。为此,本文对贴脚焊工字型铝合金中心受压杆件进行了试验研究,并将试验结果同即将颁布的国家标准《铝合金结构设计规范》及《欧洲铝合金结构设计规范》(EC9)进行了比较。研究表明,通常情况下,对于贴脚焊构件,《规范》结果和试验结果吻合较好。     

Growth characterization of anodic film on AZ91D magnesium alloy in an electrolyte of Na2SiO3 and KF

Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The corrosion resistance of the various anodized alloys was evaluated by a fast corrosion test using the solution of hydrochloric acid and potassium dichromate. The results showed that the addition of KF resulted in the presence of NaF in the anodic film. The thickness of the anodic film formed under a constant current density of 20 mA/cm2 for 16 min at 60℃ exceeded 100 μm. The growth of the anodic film could be divided into three stages based on the anodizing time; the growth rate was much faster during stage Ⅱ than in stages Ⅰ and Ⅲ. The anodic film exhibited the highest corrosion resistance for the AZ91 alloy,which is attributed to the fact that the anodization was maintained until the end of stage Ⅱ.     

等离子体电解氧化陶瓷膜的工艺研究

利用等离子体电解氧化技术在铝合金6063表面生成了氧化物陶瓷膜．测试了氧化膜表面厚度和硬度，观察了膜层表面形貌，分析了氧化陶瓷膜的成分，探讨了不同电流密度对形成陶瓷膜厚度和硬度的影响．结果表明：铝合金6063表面陶瓷膜的厚度和硬度随电流密度的增大而提高，但有一极限值平均电流密度极限值为25A／dm^2；随氧化时间的延长而增厚增硬，但也有一极限值，氧化时间极限值为45min．     

铝—石墨复合材料的制备

本文研究了铝—石墨复合材料的制备.结果表明,铝合金中添加一定量的元素钛后,可以通过向铝液中直接加入不经镀覆的颗粒石墨而制得铝—石墨复合材料.并且铝合金的含钛量和石墨粒度对于铝—石墨复合材料中的最大石墨含量有很大的影响.文中分析了这种影响的原因.     

纳米TiO2复合涂层的制备及其对LY12铝合金的防护性能影响

为了改善铝合金材料的耐腐蚀性能,研究了以正硅酸乙酯（TEOS）为主要原料,加入一定量的-氨丙基三乙氧基硅烷（KH550）,并引入纳米TiO2进行复合,以冰乙酸为催化剂,采用溶胶-凝胶法在铝合金基体表面形成复合涂层,并利用氟硅烷进行表面修饰。腐蚀电化学测试分析结果表明,纳米TiO2掺杂制备的复合涂层能够明显的提高铝合金基体的防护性能。并考察了纳米TiO2含量对涂层性能的影响,结果表明,在纳米TiO2质量分数为0.04%时制备的涂层性能最佳,相应的试样在3.5%（质量分数）NaCl溶液中的腐蚀电流密度约为5.965×10 9 A/cm2,而同等实验条件下铝合金基体腐蚀电流密度为7.216×10 5 A/cm2,涂层的存在使腐蚀速率降低了4个数量级,说明涂层对铝合金基体具有显著的防护效果,并且利用扫描电镜（SEM）和接触角测试来考察涂层的致密性和憎水性。     

Pressureless infiltration of Si3N4 preforms with an Al-2wt%Mg alloy

The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms, The growth of the composite with useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope. During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AIN. The silicon produced during the growth consumed in the formation of MgSiAIO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms, First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase （AlON）, The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.     

铝复合变质处理对M_2铸造高速钢的影响

Ｍ２铸造高速钢加铝复合变质处理后，可减小Ｗ，Ｍｏ元素偏析，加大Ｃｒ元素偏析，改善铸态与热处理后组织中共晶碳化物的形态和分布，提高机械性能。     

Cu对热挤压Al-Mg-Si合金力学性能及导电率的影响

为了满足铝合金架空输电导线的使用需求,以热挤压法制备的Al-Mg-Si合金电工铝杆为研究对象,通过调节Cu元素的添加量,研究了Cu对Al-Mg-Si合金的力学性能及导电率的影响.结果表明,向Al-0.35Si-0.45Mg-0.13Fe合金中添入微量Cu元素后,Mg2Si析出相得到细化且时效强度提高.随着Cu元素含量的增加,峰时效时间缩短,合金抗拉强度不断提高,但伸长率逐渐降低.当Cu含量为0.06%时,合金抗拉强度达到最大值145.7 MPa.合金导电率随着Cu元素含量的增加先升后降,当Cu含量为0.03%时达到最大值60.18%IACS.     

试验优化法确定阳极氧化工艺制备铝基疏水表面

通过试验优化方法,找出阳极氧化过程各因素对铝表面接触角的影响规律,确定提高铝基疏水接触角的最佳氧化工艺条件。优化结果表明,因素电流密度的极差最大,且具有显著性水平,相比氧化最低温度、氧化最高温度和氧化时间（30~60min）,对氧化膜表面疏水接触角大小的影响最突出,而氧化最低温度次之。由体式显微镜和电镜分析可知,在优化工艺下制备的铝氧化膜表面获得了具有粗糙形貌的多孔结构。通过分析发现,其疏水性服从cassie—Baxter方程。     

2A12铝合金电化学腐蚀行为研究

采取正交试验方法,利用极化曲线和电化学阻抗谱(EIS)等电化学方法研究了2A12铝合金在不同溶液浓度、pH值以及温度的NaCl溶液中的腐蚀行为。试验结果表明,溶液浓度、pH值以及温度对2A12铝合金在NaCl溶液中耐腐蚀行为的影响依次为：pH值、温度、溶液浓度。2A12铝合金的耐腐蚀性能随着NaCl溶液浓度的增加而变差;NaCl溶液温度越高,腐蚀电流密度Icorr越大,合金耐腐蚀性能下降;溶液中性条件下,合金耐腐蚀性能最强,碱性条件下耐腐蚀性能最差;酸性条件下腐蚀电流密度Icorr随pH值的降低而增大,合金耐腐蚀性能减弱。     

铝合金基板上磁控溅射离子镀氮化钛膜层的研究

对自行研制的一台磁控溅射离子镀实验裴置的放电特性进行了测试,并用该装置在硬铝(LY16)基板上进行了沉积氮化钛膜层的工艺试验,系统地研究了各工艺参数对膜层性能的影响。试验结果表明:在较低温度(120～140℃)条件下,用磁控溅射离子镀工艺可以在铝合金基体上得到组织致密质量较好的膜层,其硬度值可以达到Hv2200kg/mm~2,且仍能保持基体时效强化的强度。     

Tribological Properties of Polyvinyl Mcohol Hydrogel Reinforced with Nanometer Hydroxy Apatite

As a potential artificial cartilage material,the friction and wear properties of nano-hydroxy apatite(HA)particles filled poly(vinyl alcohol)hydrogel(PVA-H)composites sliding against stainless steel disk under water lubrication condition were studied by using a four ball tester.The worn surfaces were investigated by using a scanning electron microscope(SEM)to determine the wear mechanisms.Experimental results show that filling HA to PVA-H will slightly increase the friction coefficient of composites with the increasing of HA content under water lubrication condition.Meanwhile,HA particles can greatly reduce the wear mass loss of the PVA-H composites and enhance the load carrying capacity,the wear loss of the 1 wt% HA reinforced PVA-H composites can be decreased by 30 percent under 2.0 MPa to 50 percent under 0.5 MPa contact pressure.We also found that 2 wt% HA content of composites increase the wear mass loss under the same condition.SEM examination shows that the worn surface of low HA containing(1 wt%)composites are much smoother than that of pure PVA-H or high HA containing(2 wt%)composites under 1.5 MPa contact pressure.It is also found that there are big hole and big reunited HA particles in the surface of 2 wt% HA containing composites,which leads to deterioration of the surface of samples under higher loads in water lubrication.These results may be useful in the tribological design of artificial articular cartilage material.     

Tribological Properties of Polyvinyl Alcohol Hydrogel Reinforced with Nanometer Hydroxy Apatite

As a potential artificial cartilage material, the friction and wear properties of nano-hydroxy apatite （HA） particles filled poly （vinyl alcohol） hydrogel （PVA-H） composites sliding against stainless steel disk under water lubrication condition were studied by using a four ball tester. The worn surfaces were investigated by using a scanning electron microscope （SEM） to determine the wear mechanisms. Experimental results show that filling HA to PVA-H will slightly increase the friction coefficient of composites with the increasing of HA content under water lubrication condition. Meanwhile, HA particles can greatly reduce the wear mass loss of the PVA-H composites and enhance the load carrying capacity, the wear loss of the 1 wt% HA reinforced PVA-H composites can be decreased by 30 percent under 2.0 MPa to 50 percent under 0.5 MPa contact pressure. We also found that 2 wt% HA content of composites increase the wear mass loss under the same condition. SEM examination shows that the worn surface of low HA containing （1 wt%） composites are much smoother than that of pure PVA-H or high HA containing （2 wt%） composites under 1.5 MPa contact pressure. It is also found that there are big hole and big reunited HA particles in the surface of 2 wt% HA containing composites, which leads to deterioration of the surface of samples under higher loads in water lubrication. These results may be useful in the tribological design of artificial articular cartilage material.