EIS studies the effect of Zinc to Al-Zn alloy used for cathodic protection in 3% NaCl solution

Electrochemical impendence spectroscopy （EIS） is applied to investigate the dissolution behavior of Al-Zn alloys in 3% NaCl solution at different polarization potentials. A new reaction model is proposed, and the activation mechanism of zinc in Al-Zn alloys is achieved. There are three intermediates in the dissolution process： Znad^＋, Znad^2＋ and Alad^＋, ,of which only Zni can activate Al-Zn alloys. Most Znnd^＋ is produced by β-phase,and the alloys with 2. 3% - 3. 8% （wt） Zn dissolve rapidly. The Al-Zn alloys of heart-shaped EIS are active in 3% NaCl solution, thus EIS characteristic can be used to distinguish the activa-tion of Al-Zn alloys.

Effects of compressing and remelting in SIMA processing on semi-solid structure evolution of an Al-Zn wrought alloy

Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.

Recrystallization of the cold-deformed discontinuous precipitation microstructure in Al-Zn (-Cu) alloys

Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallizationmechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be dividedinto coarsening mainly driven by stored deformation energy at colony boundaries and slip bands andthe one mainly driven by boundary energy in the area with little deformation. It is shown that theaddition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffractionanalysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn duringthe heating process.

Study on Heating Uniformity of Pt-Rh Alloy Bushing for Producing Flexible Glass

The numerical simulation for temperature distribution of Pt-Rh alloy bushing was carried out using a thermal-electric module in ANSYS Workbench finite element analysis software.The effects of side wall thickness,plug thickness,the angle of two side walls and electrode structure on the uniformity of temperature distribution were investigated.Meanwhile,the contrastive analysis results of bushing with and without glass melt were discussed.The simulation results show that,when the homogeneous glass melt flows through bushing,the temperature difference between the center and both ends of bushing is decreased significantly,but the temperature distribution at both ends of bushing is still affected by heating non-uniformity of bushing.Compared with side wall thickness,plug thickness and the angle of two side walls,electrode structure plays a greater role in adjusting heating uniformity of bushing.

Platinum/rhodium Alloy Bushing for Drawing Glass Fibers in Centrifugal-spinneret-blow Process

In this paper,glass fibers were prepared by centrifugal-spinneret-blow(CSB) process.The molten glass got different flow rate from 390 kg/h to 270 kg/h by adjusting the electric current of platinum/10 rhodium alloy bushing.The diameter and microstructure of glass fibers have been investigated by scanning electron microscopy(SEM) and vertical optical microscope(VOM).The results indicated that the flow rate of molten glass was proportional to the diameter of glass fibers when the molten glass got main flow rate of 330 kg/h.The lower the flow rate was,the finer the average diameter was.

Structures Solidified under Microgravity in an Al-Zn Alloy

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STABLE NONLINEAR RELAXATIONS IN A MULTIPHASIC Al-Zn ALLOY

The experiments reveal the characteristics of stable damping in a multiphasic Al-Zn eutectoid alloy:（1）Thewhole damping(Q-1)has the same dependence on measured frequency（f）,i.e.Q-1ocf-n,where n is a parameterand is independent of temperature.（2）In a low-temperature（low-T）and low-strain-amplitude（low-A）region,Q-1=（B/）exp（-nH/kT）,where B is a parameter,H the atomic diffusion activation energy,k Boltzmann′sconstant,and T the absolute temperature.n,Ho（=nH）and H are all independent of A.The damping comesfrom an anelastic motion of the phase-interface.（3）In an intermediate region including a low-Tand a high-A,a middle-T and middle A and a high-T and low-A regions,the equation Q-1=（C/fn）exp（nH/kT）stillholds,but the damping has a normal amplitude effect C,n,and H all vary with A;the damping results from anonlinear relaxation of phase-interface.（4）In a high-T and high-A region,there is no longer a linear relationship between InQ-1 and T-1,whereas the relation Q-1f-n is still satisfied,where n increases as A increases,andthe damping has a normal amplitude effect but one which is weaker than that in the case（3）.The damping maybe attributed to another kind of nonlinear relaxation between phase-interfaces.

Al-Zn轴瓦合金显微组织和力学特性的研究

对采用设计化学成分制备的 Al-Zn 轴瓦合金进行显微组织观察、能谱分析和力学特性测试。结果表明：在合金化学成分设计的质量分数范围内，在 Al-Zn-Cu 基体表面分布着 Mg2Si、CuAl2、S（Al2MgCu）相、Pb 相、Sn 相和 Al（6 MnSiFe）相；合金铸锭经过 500 ℃×6 h 均匀化处理、轧制和 300 ℃×1 h 退火处理后，其抗拉强度为 180~205 MPa，伸长率为 16%~18%，显微硬度为 54.7HV。

Effects of F-Si sealer on electrochemical characteristics of 15%Al-85%Zn alloy thermal spray coating

Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al-Zn alloy wire material. Thereafter, and sealed specimens with F-Si sealer on Al-Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al-85%Zn seems to be appropriate not only in static environment but also in dynamic environment.

Effect of Cu on Discontinuous Precipitation of a Symmetrical AlZn Alloy

The effect of Cu additions on discontinuous precipitation of AlZn alloy were studied with optical microscopy, scanning electron microscopy and X-ray diffraction. It is found that the effect of addition of 2 at. pct Cu on cellular nucleation site is not remarkable, while the effect of aging temperature on cellular nucleation site of AlZn and AIZn-2Cu alloys is fairly obvious. The cell growth rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu. The discontinuous precipitation microstructure of AlZn alloy is not apparently affected with the addition of 2 at. pct Cu and the cellular front is still fine microstructure of spinodal decomposition. The phase constituents consist of a fcc Al-rich phase, a hcp Zn-rich phase and a CuZn4 phase. The transformation rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu.

Effect of Cu on the Spinodal Decomposition of AlZn Alloy with Symmetrical Composition

The effect of Cu addition on the spinodal decomposition of the Al-Zn alloy with symmetrical compositions has been investigated by X-ray diffraction analysis. It is found that the single fcc phase can be obtained in the AlZn alloy with the addition of 2 at. pct Cu after solution treatment at 400℃ and water quenching to room temperature. The modulation structure occurs in two types of alloys aged at room temperature for 30 min. The spinodal process remarkably slows down above or at the three phase equilibrium temperature, particularly at room temperature due to the addition of 2 at. pct Cu. The spinodal time increases by 20 times when aging at 300℃ and by more than 30 times when aging at room temperature.

Discontinuous Precipitation and Dissolution under the Influence of the Plastic Strain and Temperature in Al-15 at.%Zn and Al-30 at.%Zn Alloys

The discontinuous precipitation and dissolution in the alloy Al-Zn system has been the subject of many theoretical and experimental investigations that have contributed to the understanding of the different mechanisms which control them. However, many questions remain unanswered because of the complexity of the constituted phases which are affected by the speed of the quenched, deformation, the temperature of homogenization and ageing effect. The purpose of this work is to clarify the effect of temperature and deformation on the mechanisms of these two reactions during ageing of Al-15 at.% Zn and Al-30 at.% Zn alloy. The techniques of analysis used in this respect are the optical microscopy, the X-ray diffraction and the hardness Vickers.

Study on the property of AI-Sn-Pb and its bush material clad with steel strip by liquid-solid bond rolling

AISn8Pb2Si25Cu0.8Cr0.2(ASP) is a new bush material with high performance, but its bad plasticity limits itsapplication. By studying the effect of silicon content on the performance of this bush material, it was found that the alloyperformance and the distribution of tin and lead were affected by the silicon content. When the silicon content was 2.5%,most of the silicon precipitated along the grain boundary, and most of the lead and tin located along the grain boundarycontinuously, this resulted in the decrease of the bush material’s performance. When the silicon content decreased to 1.0%,it distributed more uniformly, the tin and lead phases were spheroidized and became discontinuous, the performance ofASP material was then greatly increased.

基于正交试验设计的Al-Zn轴瓦合金性能影响因素研究

以Al-Zn轴瓦合金为研究对象,基于正交试验设计方法,熔炼不同成分及对熔体保温不同时间制备合金试样,对其抗拉强度、伸长率、硬度等性能指标进行了检测,研究Zn、Si、Cu元素的含量以及熔体保温时间四因素对Al-Zn合金性能的影响。结果表明,对抗拉强度的影响显著性由大到小的因素依次为Cu、Zn、保温时间、Si;随着锌、铜含量的增加,抗拉强度逐渐升高;随着硅含量的增加,抗拉强度先升高后略有下降;随着熔体保温时间的增加,抗拉强度逐渐降低;对伸长率的影响显著性由大到小的因素依次为Cu、Zn、保温时间、Si;随着锌含量的增加,伸长率先提高后降低;随着铜、硅含量增加,伸长率逐渐降低;随着熔体保温时间的增加,伸长率先降低后升高;对布氏硬度的影响显著性由大到小的因素依次为保温时间、Cu、Zn、Si;随着锌、硅含量及熔体保温时间的增加,硬度值先升高后下降;随着铜含量的增加,硬度值逐渐升高。

CELLULAR SPACING SELECTION OF Al-0.53wt%Zn ALLOY UNDER NEAR-RAPID DIRECTIONAL SOLIDIFICATION CONDITION

In order to investigate the response of cellular spacing to the variation of growth velocity under near-rapid directional solidification condition, Al-0.53wt%Zn alloy is directionally solidified with Bridgman apparatus. The results show that at the given temperature gradient the obtained microstrvctures are all cells and there exists a wide distribution range of cellular spacing. The maximum, λmax, minimum, λmin, and average cellular spacing, λ, as functions of growth rate, V, can be given by λmax=948.51V-0.4961, λmin= 661.16V-0.5015 and λ=412.41V-0.5049, respectively. The experimental results are compared with that predicted by KGT model, and a good agreement is found. Moreover,it is found that the average cellular spacing is also remarkably history-dependent.

Effect of Mischmetal on Oxidation Resistance of 55Al－Zn Alloy Hot Dip Coating

The effect of mischmetal addition on high temperature oxidation resistance of 55wt% Al43.4 wt% Zn-1 .6wt% Si alloy hot-dip coatings has been investigated. It is found that rare earth addition improves high temperature oxidation resistance of the coatings. The oxidation tests at 800℃, 100 h and 1000℃, 50 h show that the coating with addition of 0. 1 % RE has the best properties. The morphology of oxide scale and element distribution of coating section were analysed by SEM, EPMA and XRD. It is indicated that mischmetal addition improves the adhesion between oxide scale and coating substrate, and spalling resistance of the scale is also improved with the addition of RE. Additionally, RE controls the degeneracy speed of Al-content in the coatings and inhibits the growth of Fe-Al intermetallic compound. For this reason, higher Al-content is kept in all the coatings with RE addition.

钛合金阀门衬套冷装工艺试验研究

本文针对钛合金阀门衬套结构原理进行分析,确定相应的冷装温度、冷装时间等衬套冷装工艺技术参数,同时开展-196℃液氮环境下的钛合金衬套深冷尺寸变形研究,制定相应的工艺路线,以期对钛合金阀门衬套装配起到一定的指导意义。

橡胶衬套电镀锌镍合金层与橡胶粘接工艺改进

对橡胶衬套中钢铁件电镀锌镍合金层与橡胶的粘接工艺进行改进,包括对电镀锌镍合金工艺进行优化、喷涂或刷涂较薄的底涂胶粘剂并预固化、喷涂或刷涂较厚的面涂胶粘剂。结果表明:与传统粘接工艺相比,采用改进粘接工艺的电镀锌镍合金层与橡胶的粘接力明显提高,钢铁件表面附胶率达到90%以上,粘接性能大幅提高。

轿车活塞衬套材料研究进展

活塞衬套材料是发展汽车发动机技术的关键问题。综述了汽车发动机活塞衬套使用的几种主要材料:铸造共晶硅铝合金、铅青铜、磷青铜等,介绍了铝合金和铜合金衬套材料的成分、性能及其在应用中的不足,并对活塞衬套材料的发展及应用进行了展望。

Al-Pb-Si-Sn-Cu轴瓦合金的微观结构及特征

采用机械合金化、冷压与热挤压法制备了Al 15 %Pb 4 %Si 1%Sn 1 5 %Cu(质量分数 ,% )轴瓦合金。试验结果表明 ,块体材料的组织分布很均匀。Pb粒子细小均匀弥散分布在Al基体上 ,呈纳米晶粒。Al基体晶粒大小约 1 2 μm ,在其晶界和晶粒内都有粒子析出。在Al基体上还分布着由非晶和亚微米晶粒构成的混合相。研究表明 ,该工艺是制备Al Pb系列轴瓦合金的较佳方法 ;并为制备室温不互溶、高温存在很宽固溶间隙、有较大密度差异的合金组元且组织均匀的合金奠定了工艺基础。