Effect of grain size on corrosion behavior of electrodeposited bulk nanocrystalline Ni

Nanocrystalline (NC) and coarse-grained Ni with different grain sizes (from 16 nm to 2 μm) were fabricated by direct current electrodeposition. Effect of grain size on the electrochemical corrosion behavior of these Ni deposits in different corrosion media was characterized by using potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and immersion corrosion test. Results show that in the NaOH or NaCl solution, the NC Ni exhibits improved corrosion resistance with the decrease of grain size. But in H2SO4 solution, the higher grain boundary density accelerates corrosion due to no passive process and the corrosion resistance of NC Ni decreases with refining grain size. The distinct experimental results of NC Ni in corrosion behavior can be reasonably explained by the positive or negative effect of high-density grain boundaries in different corrosion media.     

双模晶粒氧化物弥散强化合金的强化模型及热稳定性

通过透射电子显微镜、电子背散射衍射、扫描电子显微镜和室温拉伸检测等手段,建立并验证双模晶粒尺寸分布氧化物弥散强化合金的室温强化预测模型。同时,通过在1150℃下进行不同时间的热处理试验,结合组织观察和显微硬度测试,研究合金的高温组织热稳定性。结果表明:室温强化预测模型通过叠加固溶强化(σ_ss)、晶粒尺寸强化(σ_g)、位错强化(σ_d)与氧化物纳米粒子强化(σ_p)之和的平方根,模型预测结果与试验值十分接近。合金组织热稳定性研究结果表明,在1150℃热处理初期,晶粒长大迅速且合金硬度迅速降低;而当热处理时间延长到8 h之后,晶粒尺寸虽有变化但其长大速率明显放缓,且合金硬度在热处理8 h后趋于稳定。     

镍基合金大锻件成形过程流变行为与晶粒尺寸预测

基于IN718合金热态成形过程中流动应力软化特征,采用动态再结晶软化本构模型来描述锻造过程中变形-传热-微观组织演变的相互作用。借助DEFORM-3D二次开发,将本构模型和微观演变模型进行耦合,模拟预测了IN718合金在多道次锻造过程中流变行为与晶粒尺寸演变,为大锻件锻造热力参数的合理制定与控制提供了依据。     

Corrosion resistance of electrodeposited RE-Ni-W-P-SiC composite coating

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭａｋｉｎｇｕｓｅｏｆｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｓｉｓｔｈｅｄｅｖｅｌ ｏｐｉｎｇｔｒｅｎｄｉｎｔｈｅｃｕｒｒｅｎｔｍａｔｅｒｉａｌｓｓｃｉｅｎｃｅ .Ｉｔｍｅａｎｓｏｂｔａｉｎｉｎｇａｎｅｗｃｏｍｐｏｓｉｔｅｍａｔｅｒｉａｌｂｙｃｏｍｂｉｎｉｎｇｔｈｅｂｅｓｔｐｒｏｐｅｒｔｉｅｓｏｆｓｅｖｅｒａｌｄｉｆｆｅｒｅｎｔｍａｔｅｒｉａｌｓｓｏａｓｔｏｍｅｅｔｐｅｏｐｌｅ’ｓｄｅｍａｎｄｓ .Ｃｏｍｐｏｓｉｔｅｅｌｅｃｔｒｏｐｌａｔｉｎｇｉｓｏｎｅｏｆｔｈｅｍｏｓｔｕｓｅ…     

SiC颗粒尺寸对镍基复合镀层耐磨性和耐蚀性的影响

在正交实验基础上,对比研究微米SiC(平均粒径1.5 μm)和纳米SiC(平均粒径20 nm)增强复合镍基镀层的摩擦磨损行为和耐腐蚀性能.通过TEM、SEM、EDX和XRD等手段研究颗粒分散状态以及复合镀层的表面和截面形貌、成分及相结构.采用球-盘滑动摩擦磨损试验机研究复合镀层的耐磨性.电化学阻抗谱测量在3.5%的NaCl水溶液中进行.结果表明:微米级颗粒增强复合镀层可以获得更高的表面硬度,两种增强复合镀层具有相似的摩擦磨损行为.电化学阻抗谱分析表明:SiC颗粒的加入可以提高镀层的耐腐蚀性,且纳米颗粒复合镀层具有更好的耐蚀性.     

Effect of grain size on high-temperature oxidation behavior of Cu-80Ni alloy

1　INTRODUCTIONTheoxidationofunalloyedcopperandnickelhasalreadybeenstudiedindetail.Whilethehigh tem peratureoxidationofCu Nialloys ,alsostudiedanumberoftimestodate[13] ,isanexampleofarela tivelysimpleclassofscalingofbinaryalloysbyasin gleoxidant,becausethemetalsformacontinuousse riesofsolidsolutions ,whiletheiroxides ,CuO ,Cu2 OandNiO ,exhibitsmallmutualsolubilitiesandshowsignificantdifferencesinthethermodynamicstabilityandparabolicgrowthrates .Thus ,copper richalloysformexternalscales…     

Electrochemical corrosion behavior of Cu-40Ni-20Cr alloys with different grain sizes in solutions containing chloride ions

The electrochemical corrosion behavior of the two Cu-40Ni-20Cr alloys prepared by conventional casting（CA） and mechanical alloying（MA） with the different grain sizes was studied by using open-circuit potential（OCP）, potentiodynamic polarization and electrochemical impedance spectroscopy（EIS） methods in solutions containing chloride ions. The results show that the free corrosion potentials of the two alloys move towards negative values, corrosion currents increase and therefore corrosion rates become faster with the increase of chloride ion concentrations. EIS plots of CACu-40Ni-20Cr alloy are composed of single capacitive loop, while EIS plots of MACu-40Ni-20Cr alloy are composed of double capacitive loops in solution containing lower chloride ion concentrations. EIS plots of the two alloys have Warburg impedance with the increase of chloride ion concentrations. Corrosion rates of MACu-40Ni-20Cr alloy become faster than those of CACu-40Ni-20Cr alloy obviously in solutions containing the same chloride ion concentrations because MACu-40Ni-20Cr alloy is able to produce large concentrations of grain boundaries in the course of reduction in grain size by mechanical alloying.     

Influence of the alloy grain size on the oxidation behaviour of PM2000 alloy

The influence of the alloy grain size on the oxidation behaviour in air between 900 and 1400 °C of oxide dispersion strengthened PM2000 alloy was studied. The grain size of the alloy affects the morphology, the composition of the alumina scale as well as the size, composition and volume fraction of nodules formed on the alumina scale, but has only a small influence in the kinetics. In the fine-grained PM2000, grain boundaries act as rapid pathways for aluminium diffusion, leading to the establishment of a purer alumina scale than that formed on coarse-grained material. On the coarse-grained alloy, there is enough time for the nucleation of oxides other than alumina. These oxides, impeding alumina grain growth, can lead to the formation of a fine-grained alumina layer. The outward cation and inward oxygen diffusion in this fine-grained alumina layer may contribute to both the slight increase in mass-gain and the increased tendency to form nodules at the outer surface.     

标准砂在磨料粒度组成检测中的作用分析

磨料粗磨粒粒度组成检测的基本方法为筛分法。本文通过对磨料粒度组成检测时筛分条件对筛分结果的影响进行分析，得出标准砂在粒度组成检测中的两个作用：一是用来选择高精度的试验筛，二是对筛分结果进行校正，达到准确检测粒度组成，统一检测结果的目的。同时论述了标准砂的校正原理，并以实例对标准砂的作用进行了论证。     

The effect of alloy grain size on the transient oxidation behavior of an alumina-forming alloy

In the early stages of alloy oxidation, diffusion of solute through the metal to the surface is important in determining the composition of the oxide scale that forms during the transient stage. Rapid solute diffusion to the interface will promote the formation of a protective scale, thereby suppressing the formation of base-metal oxide. The effect of alloy grain size on the formation of the transient oxide scale has been studied using a very fine grained NiCrAlY alloy produced by plasma spraying. The long-term oxidation behavior of this alloy was found to be independent of the grain size of the underlying alloy. However, the short-term, transient oxidation rate was found to decrease with decreasing alloy grain size. This is attributed to the rapid grain boundary transport of Al and Cr to the oxide/metal interface which promoted the formation of Cr₂O₃ and Al₂O₃.     

变形条件对SiCp/2014Al复合材料力学行为和晶粒度的影响

研究了变形温度,应变速率和变形程度等热加工参数对ＳｉＣｐ／２０１４Ａｌ复合材料力学行为和晶粒度的影响。结果表明,该材料的流动应力对变形温度和应变速率比较敏感。变形每升高４０℃,流动应力降低５￣１０ＭＰａ,应变速率每提高一个数量级,流动应力增加１．３￣１．８们。提高应变整编有利于获得细晶组织。以足够的变形程度锻造以及适当提高锻后冷却速度均有利于获得细晶组织。根据实验结果确定了该材料的流动应力与热加工     

Corrosion Resistance of Deformed Cu-Ni Alloy in Seawater

ＣｏｒｏｓｉｏｎＲｅｓｉｓｔａｎｃｅｏｆＤｅｆｏｒｍｅｄＣｕＮｉＡｌｏｙｉｎＳｅａｗａｔｅｒＺｈｕＸｉａｏｌｏｎｇ，ＬｉｎＬｅｙｕｎ（朱小龙）（林乐耘）ＧｅｎｅｒａｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｆｏｒＮｏｎｆｅｒｒｏｕｓＭｅｔａｌｓ，Ｂｅｉｊ...     

Corrosion behavior of ultra-fine grained industrial pure Al fabricated by ECAP

Corrosion behavior of ultra-fine grained(UFG) industrial Al fabricated by equal channel angular pressing(ECAP) for 16 pass times was investigated by potentiodynamic polarization test, potentiostatic polarization test, electrochemical impedance spectroscopy(EIS) measurement, immersion test and surface analyses (OM and SEM). The microstructures including grain size, grain boundaries and dislocations were also observed by TEM. The results show that the UFG industrial pure Al has more positive pitting potential, less corrosion current density and five times larger passive film resistance compared with the coarse grained(CG) one. It was found that the increased pitting resistance is profited from the more stable passive film kept in the Cl⁻ aggressive solution due to more grain boundaries, larger fraction of non-equilibrium grain boundaries and residual stress of the UFG industrial pure Al.     

晶粒度对一些常用金属耐腐蚀性能的影响

关于晶粒度对材料的力学性能影响的研究很多,但是关于晶粒度对材料的耐腐蚀性能的研究并不常见。本文综述了几种常见钢材、有色金属及合金的晶粒大小与其耐腐蚀性能之间的关系:某些钢和铝一般随着基体材料晶粒度的减小,其耐腐蚀性能增强;铜、镁一般随着基体材料晶粒度的减小,其耐腐蚀性能减弱。分析并总结了相关的腐蚀机理。建议在获得大量腐蚀数据的前提下,开展相关人工神经网络预测模型的研究,这将有助于全面、准确的评价晶粒度对材料腐蚀性能的影响。     

含稀土HSn70-1锡黄铜的腐蚀行为研究

通过对Cu-Zn-Sn-Al-Ni-B-Mn-Sb-0.05RE和Cu-Zn-Sn-Al-Ni-B-Mn-Sb-0.1RE锡黄铜分别在NaCl(3.5%)溶液和NaCl(3.5%) NH4Cl(0.5mol/L)溶液中的腐蚀速率测定、腐蚀产物层SEM观察和XRD分析以及X射线能谱分析,研究了含稀土锡黄铜的腐蚀行为.结果表明:含稀土的锡黄铜在NaCl(3.5%)溶液中腐蚀后,腐蚀产物层薄而均匀,与基体之间的结合较好.稀土、硼等元素的添加可以明显改善锡黄铜耐Cl-腐蚀性能;在NaCl(3.5%) NH4Cl(0.5mol/L)溶液中发生了明显的沿晶腐蚀.同时,随稀土含量的增加,锡黄铜在含NH4 的人工海水介质中的耐腐蚀性能有所提高.     

4Cr14Ni14W2Mo钢的奥氏体晶粒度,孪晶及碳化物

对锻造的4Cr14Ni14W2Mo钢经相应热处理后的奥氏体晶粒度、孪晶及碳化物类型做了研究,认为固溶处理后的臭氏体晶粒度主要取决于固溶加热温度,与正常锻造温度关系不大。固溶加热过程实质也是再结晶的继续,即二次再结晶,臭氏体晶粒的大小只能通过控制再结晶温度高低和时间长短来实现。该钢热处理后,碳化物类型为M_(23)C_6和M_7C_3两种,而以M_(23)C_6最多,其中M_(23)C_6为(Cr,Fe,W,Mo)_(23)C_6和(Fe,Ni)_(23)C_6两种结构,而M_7C_3为(Cr,Fe)_7C_3。     

不同焊接电流电压下超级钢热影响区晶粒尺寸的数值模拟

.利用工程模拟软件模拟超级钢焊接温度场,在温度场模拟过程中对工件进行三维有限元网格划分,焊缝及热影响区等重要部位网格划分细密,离焊缝较远位置网格可适当稀疏.热源模型采用双椭球分布模式,利用计算机语言编制热源程序.从模拟温度场中提取热熔合线和焊接热循环曲线等信息,并实验加以验证,实验结果与模拟结果基本吻合.在热影响区温度场基础上,结合晶粒长大动力学原理计算热影响区晶粒尺寸,并实验加以验证,实验结果与计算结果基本吻合.利用此方法计算不同焊接电流、电压下热影响区晶粒尺寸,绘制晶粒尺寸图,定量预测了晶粒尺寸随电流、电压增加而增大的趋势.     

铌硼微合金化齿轮钢的晶粒尺寸及淬透性

研究了Nb-B微合金化20CrMoH渗碳齿轮钢的奥氏体晶粒长大规律及微合金化对其淬透性的影响。结果表明,添加0.04%Nb可以有效地细化奥氏体晶粒,并且在1050℃奥氏体化10h无混晶现象。此外,添加0.0008%B能够明显提高钢的淬透性,使淬透性不因晶粒细化及Nb(C,N)析出而降低。     

纳米晶WC-Co硬质合金中WC晶粒度的定量测量

通过改进金相样品的制备方法,将纳米晶WC-10Co硬质合金在场发射扫描电镜10万倍放大倍率下可获得衬度良好、WC晶粒轮廓清晰的二次电子像.采用截距法定量测量了合金中WC晶粒尺寸,结果表明:WC晶粒尺寸分布范围为12～109 nm,平均晶粒尺寸45 nm,对应的三维WC平均晶粒度为70 nm.根据合金中WC在低角度(2θ≤50°)的(001)WC,(100)Wc和(101)wc晶面衍射峰数据,用X射线衍射Scherrer公式测定的WC晶粒度的统计平均值为91 nm,与定量金相分析结果接近并且都进入了纳米尺度范畴.实验还比较了WC晶粒的统计数量和人为因素对评估数据的影响.