利用热模拟试样模拟TiNi合金激光焊接接头焊缝热影响区, 对焊接接头、焊缝金属、模拟热影响区和母材的相变温度进行差热分析, 研究了焊接接头与其它三者逆相变温度的关系, 并利用OM, SEM和XRD对母材、热影响区和焊缝金属的组织、析出相的分布以及晶体结构进行了研究. 结果表明,TiNi合金激光焊接接头的形状恢复率与母材无明显差别, 但形状恢复温度区间与母材差异较大, 其形状恢复开始温度比母材低40 ℃; 焊缝金属和热影响区逆相变开始温度(A_s)和结束温度(A_f)均不同于母材,主要原因是焊缝金属经历了熔化-凝固过程, 失去了母材中原有的晶体择优取向,且析出相尺寸小、分布不均; 而热影响区A_s和A_f降低,可能是细小析出相重新固溶于基体所致. 整个接头的逆相变温度区间与焊缝金属近似,调控焊缝金属的相变温度是控制TiNi合金激光焊接接头形状记忆功能的关键.

In order to control the shape memory function of TiNi alloy weld joint, it is necessary to clarify the effect of the three different parts (weld metal, heat-affected zone (HAZ) and base metal) on the shape recovery temperatures of the whole weld joint, but few reports are available on this aspect. In this work, the microstructure in the HAZ was studied by Gleeble thermal-simulation test. Phase transformation temperatures of weld joint, weld metal, HAZ and base metal were measured by differential thermal analysis. The inverse phase transformation temperature was analyzed. The microstructure, distribution of precipitation and crystal structure were investigated by using OM, SEM and XRD. The weld joint shows the similar shape recovery ratio to the base metal, but the shape recovery temperature range is significantly different. The start recovery temperature of the weld joint is lower about 40 ℃ than that of the base metal. Both of the austenite start temperature (A_s) and finish temperature (A_f) of the weld metal and HAZ vary much compared with the base metal. The change in the weld metal is attributed to the fusion-solidification process, in which the preferred crystal orientation is lost. The newly formed precipitation phases show a small size and an uneven distribution. The change in the HAZ refers to the drop of A_s and A_f, which is possibly caused by the solution of minor precipitation phase in the matrix. The A_sand A_f of the laser weld joint are quite the same as those of the weld metal for TiNi shape memory alloy, which indicates that the key to guarantee the shape memory function lies in controlling the phase transformation temperatures of the weld metal.

为揭示磁脉冲成形的增塑机制, 采用理论分析与微观组织观察相结合的方法对5052铝合金板材磁脉冲动态拉伸过程中动态成形行为和塑性失稳机制进行了系统研究. 结果表明, 惯性力在动态成形中起主要作用,惯性力对试样的结构失稳具有抑制作用, 从而使试样的塑性提高并产生分散失稳;5052铝合金动态成形和准静态成形的成形性质相似, 不会产生特殊的组织结构,塑性变形机制均为位错滑移机制; 准静态成形过程以均匀单系位错滑移为主,断裂伴随着位错的缠结和攀移; 而动态成形过程中, 位错滑移趋于多系开动,在大面积区域出现明显的交滑移现象, 且滑移带较准静态成形时窄且密,位错组态更均匀; 动态成形的多系滑移和位错均化作用可在比准静态成形高的多的塑性应变水平下形成, 从而使材料表现出较高的塑性和强度.

In order to reveal the hyperplasticity mechanism of electromagnetic forming (EMF), the plastic instability mechanisms and formation behaviors of 5052 aluminum alloy sheets in pulsed magnetic tension process were investigated by theoretical analysis and microanalysis. Results show that inertia force plays an important role in dynamic forming, which has the suppression effect on structural instability and thus improves the formability of sheet and spreads instability. The nature of dynamic formation is much similar with that of quasi--static formation and no special formation structures arise in dynamic process for 5052 aluminum alloy sheets. The formation mechanism of both processes is dislocation slip mechanism. For quasi--static formation, the dislocations show a uniform single--slip pattern, fracture combined with dislocation tangling and climbing. While for dynamic formation, dislocation system tends to more slips, large areas showing clear cross-slip structures. The dislocation bands are narrower and much denser than those shown in the quasi--static process, and a much more uniform dislocation configuration is also exhibited after pulsed magnetic loadings. The characteristics of multi--slips and uniform effect of dislocations under pulsed magnetic loading conditions will result in much higher plasticity and strength of materials.

对比研究了高温轧制制备的Mg-1.02Zn及Mg-0.76Y(质量分数, %)合金在不同温度退火条件下的组织演变及静态再结晶和晶粒长大动力学行为. 结果表明, Mg-1Zn合金的轧制组织以剪切带和孪晶为主, 在剪切带和孪晶内伴随着动态再结晶; 而Mg-1Y合金的轧制组织中只有孪晶, 未观察到剪切带和再结晶发生. 退火过程中, Mg-1Zn合金静态再结晶过程主要受控于形核过程, 而Mg-1Y合金则既受控于形核过程又受控于长大过程. 利用经典的JMAK模型和长大模型分别描述了2种合金热轧制后的静态再结晶和晶粒长大动力学过程, 结果表明, 静态再结晶过程的Avrami因子n值与理想预测值偏离可能来自于再结晶的不均匀形核. 固溶稀土Y原子比Zn原子对晶界移动的拖曳作用更强, 导致Mg-1Y合金比Mg-1Zn合金晶粒长大因子n'更高.

Wrought Mg alloys alloyed with rare elements (RE) addition were deemed to be one of the most promising Mg alloys in industrial application, due to the formation of weakened texture and refined microstructure. Generally, the wrought Mg alloys with RE addition after normal thermal-mechanical processing possessed incompletely recrystallized microstructure, so it was necessary to research the subsequent annealing treatment for controlling the microstructure. Unfortunately, the corresponding investigations on the mentioned above were still limited. In this study, hot-rolled Mg-1.02Zn and Mg-0.76Y (mass fraction, %) alloys were selected to investigate the microstructure evolution, static recrystallization behavior and grain growth kinetics under different annealing treatments. The microstructure examination showed that hot-rolled Mg-1Zn alloy was composed of shear bands and twins with the occurrence of dynamic recrystallization; whereas only twins were observed in the hot-rolled Mg-1Y alloy, no shear bands and recrystallization were detected. That should be attributed to the difference in the deformation modes during rolling processing. After isothermal annealing for the two alloys, recrystallization occurred in some remaining twins, whereas no recrystallization took place in others. EBSD analysis revealed that low angle grain boundaries or orientation differences were observed in the remaining twins with recrystallization, suggesting that recrystallization should be associated with the levels of stored deformation energy. The process of static recrystallization and grain growth kinetics were described by the JMAK model and grain growth model, respectively. The process of static recrystallization for the Mg-1Zn alloy was mainly dominated by the process of nucleation; while that for the Mg-1Y alloy was both controlled by the process of nucleation and growth, resulting in finer grain size. Moreover, the results showed that the Avrami exponent of recrystallization n≈1 deviated from the expected value in theory n=4, which could be due to the non-random recrystallization sites in the deformed alloys. Lower value in the grain growth exponent n' was obtained for Mg-1Y alloy than that for Mg-1Zn alloy, which may be ascribed to the stronger dragging effect of the solute Y element on the grain boundaries than that of solute Zn element.

根据《油船货油舱耐蚀钢性能标准》规范, 通过浸泡实验测量了AH32耐蚀钢在货油舱底部模拟环境中的腐蚀过程. 采用失重测量、电化学极化与阻抗方法、扫描电镜和电子探针等手段, 分析了AH32耐蚀钢显微组织对其腐蚀行为的影响. 实验结果表明: 模拟货油舱底板腐蚀实验中, AH32耐蚀钢的轧制面因珠光体所占面积分数小而腐蚀速率较低, 其横截面则因珠光体面积分数大而造成腐蚀速度较快, 而且二者的腐蚀速度均随浸泡时间的延长而加速. 此外, 轧制面表面有均匀腐蚀和因夹杂物溶解所形成的蚀坑, 而横截面的腐蚀则沿条带状珠光体组织而有选择的进行. 样品的珠光体区域在浸泡后有碳富集, 这是造成腐蚀随浸泡时间延长而加速的原因.

International martime organization (IMO) has approved<Performance standard for corrosion resistant steel for cargo oil tanks of oil tankers>and considered corrosion resistant steel as the only alternative for anti-corrosion coating since May 2010. The implementation of the standard will have a profound impact on ship building, steel, shipping and other industries. At present, Japan has a relatively mature technology, South Korea has completed the pre-development work, while China has only carried out some preliminary studies. If the technology is blocked, a large number of steel needs to be imported which would push up the cost of construction of the shipbuilding industry, and has a direct impact on the orders of shipping enterprises. The amount of steel for cargo oil tank in China is more than two million tons each year, and therefore, the localization of research and application of corrosion resistant steel for cargo oil tanks has become an urgent task. The impact of microstructure of the existing shipbuilding steel on corrosion behavior in simulated corrosion environment is studied based on the standard in this paper to develop our own corrosion resistant steel. According to the standard, immersion test was used to measure the corrosion process of AH32 corrosion resistant steel in the bottom simulated environment of cargo oil tanks. Using gravimetric measurement, electrochemical polarization and impedance methods, scanning electron microscopy and electron probe et al, the influence of microstructure of AH32 corrosion resistant steel on its corrosion behaviors was analysed. The experimental results showed that: during the test simulating the corrosion of the bottom plate of cargo oil tanks, corrosion rate of the rolling surface of AH32 corrosion resistant steel was low with small area fraction of pearlite, corrosion rate of the cross section was fast due to the big area fraction of pearlite, and both corrosion rate increased with the immersion time. In addition, there were uniform corrosion and the pits formed by dissolved inclusions in rolling surface, and corrosion of the cross-section was selected along the banded pearlite. The carbon enriched in pearlite area of the sample after immersion, which caused corrosion rate increased with the immersion time.

为研究DZ483合金在凝固过程中的元素偏析行为对糊状区内液相密度的影响, 采用等温凝固结合水淬法对合金进行不同温度下的凝固实验. 利用OM 和SEM观察试样的凝固组织, 利用EDS测量固相和剩余液相的元素含量, 并根据剩余液相的成分计算其密度. 结果表明,  DZ483合金的开始凝固温度略低于1335℃, 在1325℃液相中开始析出富含Ta和Ti的MC; W和Co为负偏析元素, Mo, Ta和Ti为正偏析元素, 而 Al和Cr几乎不发生偏析; 剩余液相的密度随温度降低基本呈下降趋势, 但在1325至1315℃之间有所回升. 计算结果表明, 温度对液相密度的影响很小,合金元素的偏析对液相密度的影响占主要地位. 其中, Mo和Ta的偏析导致液相密度增加, 而Ti和W的偏析导致液相密度明显降低. 各合金元素的偏析对密度变化的贡献由大到小顺序为: Ti>Ta>W>Cr>Mo>Al>Co. MC的形成消耗了大量的Ti和Ta, 对合金元素的偏析造成一定的影响, 从而导致液相密度在1325至1315℃ 之间有所增加.

Ni-based superalloys have been widely applied in advanced aeroengine as gas turbine blades and vanes. The freckles in superalloys formed during directional solidification have deleterious influence on the properties of the alloys. The generation of freckles is associated with the local liquid density gradient in the mushy zone, which is obviously influenced by microsegregation of alloy elements. However, the individual contributions of the various elements to the total density variation are still not well known. Therefore, the effect of microsegregation on the liquid density variation in DZ483 Ni-based superalloy was investigated by isothermal solidification together with liquid quench method. Solidification microstructures were observed by optical microscope and SEM, and the compositions of the solids and the residual liquid were determined by EDS. Based on the compositions of residual liquids, the densities of liquids at different temperatures were calculated. The results show that the onset solidification temperature of DZ483 alloy is a little bit below 1335℃, and MC, which is enriched with Ta and Ti, formed at about 1325℃. The segregation coefficients of different elements show that W and Co are negative segregation elements, Ta and Ti positive segregation elements, while Al and Cr show little segregation. The density of the residual liquid generally decreases as the decrease of temperature, with the exception that it increases somewhat from 1325 to 1315℃. Calculation results show that temperature has insignificant influence on liquid density, and variation of density is mainly due to microsegregation. Segregations of Mo and Ta lead to the increase of density, but segregations of Ti and W present opposite effect. Contribution of each element to the variation of the liquid density is analyzed. The sequence of contributions of alloy elements to the variation of total liquid density is TiTa>W>Cr>Mo>Al>Co. The formation of MC consumes an abundant of Ti and Ta, resulting in the increase of liquid density from 1325 to 1315 ℃.

研究了电弧离子镀磁性靶材使用过程中发生“跑弧”并导致靶材无法稳定刻蚀的问题. 利用有限元方法(FEM)对外加磁场下非磁性靶材系统和磁性靶材系统中的磁场分布进行了模拟. 研究了外磁场对电弧斑点运动的影响机理, 并结合电弧斑点放电的物理机制, 探讨了磁性靶材与低饱和蒸气压金属靶壳、绝缘陶瓷靶壳或软磁性金属靶壳组成复合结构靶材解决磁性靶材使用问题的可行性. 结果表明, 这3种复合结构靶材设计方案均能有效解决电弧离子镀磁性靶材“跑弧”问题. 通过实验得到, 在低饱和蒸气压金属或绝缘陶瓷靶壳设计方案里, 靶材频繁引弧到弧斑能受控运动的转变温度为(136.6±23.0) ℃.

Arc ion plating (AIP) has been widely used for depositing various kinds of coatings due to the excellent characteristics of high deposition rate, convenient parameter control, high degree of ionization in the target material, good coating--substrate adhesion, flexibility of target arrangements and merits of producing coatings with high packing density. Magnetic films, with a few micrometers or less, could be utilized in the electronics industry, such as magnetic recording, magnetic microelectromechanical systems, magneto optical modulator, and so on. In AIP process, due to magnetic shielding and self--induced magnetic field, arc spot on the surface of the magnetic target moved outside all the time, and the erosion of the magnetic target could not be stable. In this study, arc spot outside moving and unstable erosion of the magnetic target in arc ion plating have been investigated. The distribution of the magnetic field of the nonmagnetic target and the magnetic target under an additional magnetic field was simulated by the finite element method (FEM). The effect of magnetic field on the arc spot movement was researched. With the physical mechanism of the arc spot discharge, the feasibility on the solution of the application problem of the magnetic target has been discussed by the program of the composited structure target, which were composed of magnetic target materials and target shell of low saturation vapor pressure metal, target shell of insulating ceramics, or target shell of soft magnetic metal. The results showed that all these solutions could solve the problem of arc spot outside moving efficiently. In the study, the transition temperature is (136.6±23.0) ℃ in the solutions of the target shell of low saturation vapor pressure metal or insulating ceramics, during which the arc striking frequently transformed to the controlled movement of arc spot.

采用多靶磁控溅射技术, 分别利用不同V靶功率和石墨靶功率制备一系列不同V含量和C含量的TiVN和TiVCN复合膜.利用X射线衍射仪、纳米压痕仪、高温摩擦磨损仪研究了TiVN和TiVCN复合膜的微结构、力学性能及室温和高温摩擦磨损性能.研究表明, 当V靶功率为60 W时, TiVN薄膜的硬度达到最大值, 为25.02 GPa. 在此基础上逐渐加入C元素, 当石墨靶功率为20 W时, TiVCN薄膜的硬度达到最大值, 为28.51 GPa. 当石墨靶功率进一步增加, 薄膜的硬度值开始逐渐降低. 室温下, 随着石墨靶功率的增加, TiVCN薄膜的摩擦系数逐渐减小. 高温下, TiVCN复合膜的摩擦系数随着温度的升高先增加后减小, 在700℃时获得最小值, 当温度继续升高摩擦系数又增加. 讨论了高温下TiVCN复合膜Magneli相的作用和自适应机制.

A series of TiVN and TiVCN nano-composite films with different V and C contents were synthesized using a multi-target magnetron sputtering technique. The microstructures, mechanical properties and friction properties at different test temperatures were investigated by X-ray diffraction, nano-indentation, CSM high-temperature ball-on-disc tribo-meter and SEM-EDS analysis. The results showed that the hardness values of the TiVN and TiVCN films reached maximum of 25.02 GPa and 28.51 GPa at a V target power of 60 W and C target power of 20 W, respectively. With the further increase of C, however, the hardness of TiVCN films decreased gradually. At room temperature, the friction coefficient of the TiVCN film decreased with the increase power of C target. At high temperature, the friction coefficient of the TiVCN showed a up-down-up curve with the increase of test temperature. The effects and adaptive mechanisms of Magneli phase formed in the TiVCN films at high temperature were discussed.

采用弹塑性应力--应变有限元方法计算了[111]取向镍基单晶合金中γ/γ'两相共格界面的von Mises应力及应变能密度分布, 研究了施加拉应力对γ/γ'两相界面von Mises应力分布及γ'相定向粗化规律的影响. 结果表明: [111]取向镍基单晶合金经热处理后, 组织结构是立方γ'相以共格方式嵌镶在γ基体相中, 沿<100>方向规则排列. 当沿[111]取向施加拉应力蠕变期间, 与近(010)_γ'晶面的基体通道相比, 近(001)_γ'和(100)_γ'晶面的基体通道有较大的von Mises应力,在主应力分量的作用下, (100)和(001)晶面分别沿[001], [010]和[010], [100]方向发生较大的晶格扩张应变, 可诱捕较大半径的Al和Ti原子, 这是促使γ'相在(010)面沿[001]和[100]方向定向生长成为层片结构的筛网状筏形组织的主要原因.

The distribution of von Mises stress and strain energy density in regions near interfaces of γ/γ' phases was calculated by an elastic--plastic stress--strain finite element method (FEM), and the influences of applied stress on the von Mises stress distribution and coarsening regularity of γ' phase in a [111] oriented single crystal nickel--based superalloy were also investigated. The results show that, after heat treated, the microstructure of the [111] oriented single crystal superalloy consists of a cubical γ' phase embedded coherently in γ matrix, and the cubical γ' phase is regularly arranged along <100> direction. When tensile stress is applied along [111] direction, compared to (010)_γ' plane, larger expanding lattice strain occurs on (100)_γ' and (001)_γ' planes under the action of principal stress component, which may trap Al, Ti atoms with bigger radius to promote γ' phase directionally growing along [010] and [100] orientations on (010) plane, this is thought to be the main reason of γ' phase grown directionally into a mesh--like rafted structure along (010) plane.

对一种含3%Ru(质量分数, 下同)的第四代镍基单晶高温合金的热处理态组织中的γ'相尺寸及分布情况、亚晶及嵌镶结构、γ'两相点阵错配度、γ'相体积分数等进行了表征. X射线衍射实验结果表明, 该合金不是一种完整的单晶合金, 而是由许多相邻平均取向偏差为0.5°左右、最大取向偏差为3°左右的亚晶组成, 亚晶存在亚晶界. 每一个亚晶又是由大量的嵌镶结构组成, 嵌镶结构之间的取向偏差为0.1°---0.2°. 实验结果表明, 这种合金的热处理态组织中存在明显的组织不均匀现象, 呈枝晶状分布. 该合金的平均γ'相尺寸为 0.39 μm, 平均γ'相体积分数为69.5%, 平均γ'两相点阵错配度为--2.0×10^-3. 讨论了这种合金热处理态组织的演变规律.

The microstructure of a Ru--containing single crystal nickel-based superalloy, which is a potential fourth generation single crystal nickel-based superalloy heat treated, has been investigated. The X--ray diffraction (XRD) results indicate that this single crystal superalloy is not a perfect monocrystal, which is comprised of many subgrains with an average neighboring misorientation difference about 0.5° and the maximum misorientation deviation about 3°; and each subgrain includes large numbers of mosaic structures with misorientation difference of 0.1°---0.2° between each other. It is found that the microstructure of the heat treated alloy is of heterogeneity, where the volume fraction of γ' phase increases and the γ' lattice misfit decreases. It is shown that the average size of γ' phase is 0.39 μm, the average γ' volume fraction 70% and the average γ' lattice misfit --2.0×10$^-3. The evolution of this microstructure was also briefly described.

采用掺杂Sc₂O₃, 通过固相反应法制备了CaZr_1-xSc_xO_3-α(x=0, 0.1, 0.15)材料. 在610---850℃采用交流阻抗谱法测定了CaZr_1-xSc_xO_3-α的电导率及电导激活能, 并对CaZrO₃掺Sc及掺In样品的电学性能进行了比较. 结果表明: 在610---850℃,CaZrO₃的电导率为4.3×10$^-19---1.4×10^-6 S/cm,CaZr_1-xSc_xO_3-α(x=0.1, 0.15)的电导率为1.16×10^-4---1.4×10^-3S/cm,CaZr_1-xIn_xO_3-α(x=0.1, 0.15)的电导率为0.34×10^-4---4.33×10^-4 S/cm, 且随着温度的升高而提高; 掺杂能极大提高CaZrO₃的电导率, 并随着掺杂量的增加, 电导激活能降低, 电导率增加; 温度及掺杂量相同时, 掺Sc材料电导率明显高于掺In材料, 说明掺Sc对提高材料的电导率更有效.

CaZrO₃ solid state electrolyte displays proton conductivity and high chemical stability. The Sc doped CaZrO₃ proton conductors were prepared by solid state reaction in order to improve the conductivity in this study. XRD analysis suggest that CaZr_1-xSc_xO_3-α(x=0, 0.1, 0.15) samples were synthesized completely. The electrochemical impedance spectra were applied to study the conductivities and the activation energy for proton diffusion of the CaZr_1-xSc_xO_3-α(x=0, 0.1, 0.15) in the temperature range of 610---850℃, and the electric conductivities of CaZr_1-xSc_xO_3-α were compared with those of CaZr_1-xIn_xO_3-α. The experiment results show that the electric conductivities of CaZrO₃, CaZr_0.9Sc_0.1O_3-α, CaZr_0.85Sc_0.15O_3-α, CaZr_0.9In_0.1O_3-α and CaZr_0.85In_0.15O_3-α are 4.3×10^-19---1.4×10^-6 S/cm (610---850℃), 1.16×10^-4---4.6×10^-4 S/cm (690---850℃), 1.8×10^-4---1.4×10^-3 S/cm (610---850℃), 0.34×10^-4---4.30×10^-4 S/cm (741---847℃) and 0.57×10^-4---4.33×10^-4 S/cm (585---814℃), respectively. These conductivities results show that the conductivity of CaZrO₃ proton conductor can be significantly improved by doping. The conductivities of CaZrO₃ increase with the Sc doping content and temperature increasing. The results reveal that the conductivities of CaZr_1-xSc_xO_3-α are higher than those of CaZr_1-xIn_xO_3-α. Sc--doping is more beneficial for increasing the conductivity of CaZrO₃ solid state electrolyte.

采用电弧离子镀技术在NiCrAlY涂层与O相Ti₂AlNb合金之间沉积不同Al∶Al₂O₃比例的 Al--Al₂O₃薄膜作为扩散阻挡层. 研究了900 ℃下恒温氧化500 h后NiCrAlY/Al--Al₂O₃/Ti₂AlNb 体系中Al--Al₂O₃层阻挡合金元素互扩散的行为, 以及对涂层氧化动力学曲线的影响. 结果表明, 没有添加扩散阻挡层的NiCrAlY/Ti₂AlNb体系, 涂层和基体之间的元素互扩散十分严重, 涂层丧失抗氧化能力；而添加扩散阻挡层的材料体系, 涂层和基体之间的元素互扩散受到抑制, 涂层的长期抗高温氧化性能得到提高. 对于3Al--Al₂O₃, 1Al--Al₂O₃和0Al--Al₂O₃~3种扩散阻挡层, 综合比较材料体系的抗氧化性能、阻挡层阻挡涂层和基体元素互扩散能力、以及涂层和基体之间结合力, 当1Al--Al₂O₃薄膜作为扩散阻挡层时, 材料性能最优异. 同时, 本文利用扩散阻挡系数简洁定量地表示出不同Al∶Al₂O₃比例阻挡层的阻挡扩散能力.

The orthorhombic Ti₂AlNb alloys have received significant attentions because of their good physical and mechanical properties. However, these orthorhombic alloys face problems of oxidation at high temperature, especially above 700 ℃. To solve these problems, the use of surface coatings is an efficient way. However, when single coating was applied on the orthorhombic Ti₂AlNb alloys, problems of serious interdiffusion and interfacial reaction were encountered, which resulted in worse oxidation behavior and deteriorated mechanical properties. To obtain good oxidation protection of NiCrAlY coating on the orthorhombic Ti₂AlNb alloy, an efficient diffusion barrier should be added. In this study, NiCrAlY/Al--Al₂O₃ double--coatings were deposited on the orthhombic--Ti₂AlNb alloy by arc ion plating. NiCrAlY coating acted as oxidation resistance coating and Al--Al₂O₃ coating acted as diffusion barrier. By introducing metallic Al in the Al₂O₃ film, the problem of coefficient of thermal expansion (CTE) mismatch between film and alloy substrate might be mitigate. Also metallic Al in the Al₂O₃ film can act as diffusion path which permits proper interdiffusion to improve the interface adhesion. The oxidation and interdiffusion behavior of specimens with and without diffusion barriers were investigated by oxidation tests at 900 ℃. The results indicated that substantial interdiffusion and rapid oxidation degradation occurred in the coated specimens without diffusion barrier. With Al--Al₂O₃ diffusion barriers, deferred interdiffusion and improved oxidation resistance were observed. Different contents of metallic Al in the Al₂O₃ coatings had different efficiency of diffusion barrier, and also affected interfacial mechanical properties. Among these NiCrAlY/Al--Al₂O₃ coatings, double--coating containing 1Al--Al₂O₃ diffusion barrier exhibited best performance. Coefficient of diffusion hindering was used to compare and quantify the efficiency of the diffusion barriers.

将La_0.7Ca_0.3Cr_0.97O_3-δ (LCC)连接材料引入到NiO/YSZ阳极中, 制备NiO/YSZ/LCC 三相复合阳极, 并进行烧结特性、微观结构、电导率、热膨胀系数等性能对比测试. 结果表明, NiO/YSZ/LCC新型复合阳极具有优良的综合性能. 采用浆料浸渍法在NiO/YSZ/LCC阳极支撑体两个表面上分别制备LCC和YSZ湿膜, 1400℃空气条件下三层共烧4 h后, 获得致密LCC连接体和YSZ电解质薄膜.

Developing cost-effective methods to prepare dense ceramic interconnect membrane for solid oxide fuel cell (SOFC) stacks is currently considered as a major technical obstacle. In order to improve the co-firing compatibility of LaCrO₃-based interconnects with the traditional YSZ-based SOFC anode support NiO/YSZ, interconnect material of  La_0.7Ca_0.3Cr_0.97O_3-δ(LCC) was introduced to NiO/YSZ anode. Triple-phase composite NiO/YSZ/LCC was prepared, and then examined as novel anode support. Sintering character, microstructure, electrical conductivity, and thermal expansion coefficient of the composite anode were investigated in detail as a function of LCC addition, respectively. Results indicated that the NiO/YSZ/LCC composite anode had excellent overall performance. Furthermore, by using a simple drop-coating process, LCC and YSZ wet membranes were prepared on the opposite surfaces of NiO/YSZ/LCC support, respectively. Followed by three-layer co-firing at 1400℃ in air for 4 h, dense La_0.7Ca_0.3Cr_0.97O_3-δ interconnect and YSZ electrolyte thin membranes were both successfully prepared on the porous NiO/YSZ/LCC anode support. This work presents a simple drop-coating/three-layer co-firing technical route for developing dense interconnect and electrolyte membranes for YSZ-based SOFC stacks.

研究了Fe--18Mn低C高Mn TRIP/TWIP钢在应变速率范围为1.67×10^-4---10³ s^-1的室温拉伸实验过程中力学性能和组织的变化. 在准静态拉伸应变速率范围内(1.67×10^-4---1.67×10^-1 s^-1), 应变速率对高Mn~TRIP/TWIP钢的抗拉强度产生逆效应, 随着应变速率的加快, 抗拉强度和延伸率都降低; 而在动态拉伸应变速率范围内 (10¹---10³ s^-1), 应变速率对高Mn TRIP/TWIP钢的延伸率产生逆效应, 抗拉强度和延伸率都随着应变速率的加快而增加; 在应变速率为10³ s^-1时, 高Mn TRIP/TWIP钢抗拉强度可达到957 MPa, 延伸率达到55.8%, 具有较好的综合力学性能; 随着应变速率的提高, 马氏体转变量减少, 孪生变形向多个方向发展. 采用SEM, TEM和XRD等方法对变形前后的组织进行了分析, 在所有应变速率范围内的拉伸变形过程中都产生了奥氏体向马氏体转变和形变孪晶, 并且在应变速率为10³ s^-1 的高速拉伸过程中产生绝热温升效应, 使得基体软化.

The microstructure and mechanical properties of Fe--18Mn low carbon high manganese TRIP/TWIP steels during tensile tests in the range of initial strain rate of 1.67×10^-4---10³ s^-1 at room temperature were studied. The inverse effect of strain rate on strength of steel was produced, the strength and ductility of steels decreased with increasing strain rate in the range of quasi--static tensile strain rate of 1.67×10^-4---1.67×10^-1 s^-1. While inverse effect of strain rate on ductility of steels was produced in the range of dynamic tensile strain rate of 10¹---10³ s^-1, the strength and ductility of materials increased significantly with increasing strain rate. The tensile strength of high manganese TRIP/TWIP steels was 957 MPa and their elongation was 55.8%. These results indicated that Fe--18Mn steel had excellent mechanical properties and good fracture resistance. The higher the strain rates applied, the less martensite, the more directions of deformation twins. The microstructure evolution of the specimen was analyzed by SEM, TEM and XRD, martensitic transformation and deformation twins were produced during the tensile deformation, and adiabatic temperature rise effect made the matrix softening during the high--speed deformation.

采用不同轧制及热处理工艺制备了化学成分相同而晶粒尺寸不同的3种超低碳IF钢试样. 采用浸泡腐蚀、周浸腐蚀、原子力显微镜(AFM)及扫描电镜(SEM)微观分析、电化学阻抗测试等手段对晶粒尺寸与IF钢耐大气腐蚀性能之间的规律进行了研究. AFM及SEM微观分析结果表明, 随着晶粒尺寸从15 μm增加到220 μm, 超低碳IF钢浸泡腐蚀后晶界处的局部腐蚀更加严重, 腐蚀裂纹处的深度加深, 裂纹宽度变宽. 超低碳IF钢晶粒尺寸从15 μm增加到46 μm, 周浸腐蚀实验后锈层中空洞和裂纹增多, 锈层电阻下降, 耐候性下降; 晶粒尺寸进一步增大到220 μm后, 锈层整体致密性得到增加, 锈层电阻上升, 耐候性得到增加. 对晶粒尺寸影响耐大气腐蚀性能的机理进行了讨论. 晶粒尺寸增大后晶界能的减少使得腐蚀表面的宏观总体缺陷数量有所减少, 耐候性有所提高; 但是晶粒尺寸增大后晶界处因局部腐蚀电流密度增大将会在局部造成更深的腐蚀坑槽并降低耐候性; 晶粒尺寸的变化对钢铁材料耐大气腐蚀性能的影响不仅要考虑其对晶界局部腐蚀电流密度的影响, 而且还必须考虑对基体整体晶界能所造成的影响.

Three kinds of ultra-low carbon IF steel with different grain sizes, and same chemical composition were prepared by different rolling and heat treat process. The relationship between grain size and atmospheric corrosion resistance of IF steel was investigated by immersion corrosion test, cyclic immersion corrosion test, AFM/SEM micro-analysis and electrochemical test. The results show that the local corrosion in grain boundary increases after immersion corrosion test, the depth of crack in grain boundary becomes deeper and the width of crack becomes wider with grain sizes of IF steel increase from 15 μm to 220 μm. The crack and cavity in the rust after cycle immersion corrosion test are increased and the atmospheric corrosion resistance is decreased with IF steel grain size coarsing from 15 μm to 46 μm. As grain size increase from 15 μm to\linebreak 220 μm, the whole compactness of rust are increased, the rust resistance and the atmospheric corrosion resistance are increased. The effect of grain size on the corrosion current density of local grain boundary was analysed and the mechanics of corrosion was discussed. The total quantity of corrosion surface defect is decreased due to the decrease of grain boundary energy with the increase of grain size and the atmospheric corrosion resistance is increased. Meanwhile, the local corrosion near the grain boundary is increased duo to the increase of local corrosion current density with the increase of grain size and the atmospheric corrosion resistance is decreased. The atmospheric corrosion resistance is influenced by the two factors simultaneously.

用TEM, OM, SEM和Vickers硬度仪测定、表征了铸态、固溶+时效态下不同La含量 AZ91合金的显微组织和析出相的形态和尺寸以及硬度变化, 研究了不连续β相和Al₁₁La₃相的形貌对合金硬度的影响及其机理, 并计算时效过程中 Al原子的扩散系数. 结果表明, 不同La含量AZ91合金在170 ℃时, La含量为0.16%的合金时效24 h达到的硬度最大, 为138 HV; 延长时效时间和改变La含量可使不连续脱溶相转变为板条状连续脱溶相, 降低Al原子的扩散系数, 从而影响不连续β相的数量、大小与分布; 晶界处的Al₁₁La₃相的形貌虽不受热处理过程影响, 但却制约β相的长大. 可见控制La含量和时效时间, 可改善不连续(片层)β相的尺寸和数量, 有效地提高合金强韧性能.

The changes of microhardness, microstructures and precipitation phase morphologies of as--cast and aged AZ91 alloys with different La were characterized by TEM, OM, SEM and Vickers. The influences of discontinuous β phase and Al₁₁La₃ on AZ91 magnesium alloy were discussed and the diffusion coefficient of Al atom in the aging process was calculated. The results showed that the alloy with 0.16%La aged at 170 ℃ for 24 h has the largest hardness (138 HV). By extending aging time and adding La element, the discontinuous precipitation phases was transformed into continuous lath--sharped phases and the diffusion coefficient of Al atom was decreased, the volume and distribution of β phase were changed. During the process of heat treatment, the topography of Al₁₁La₃ in grain boundary was not changed, but the anchoring effect of Al₁₁La₃ restricted the growth of β phase. By controlling the content of La and parameters of aging treatment, the volume and size of β phase were changed, in the mean time the strengthening and toughness properties of alloys can been improved effectively.

建立了模拟二元合金树枝晶生长的三维元胞自动机模型, 以Al-4%Cu(质量分数)为模型合金, 模拟了合金过冷熔体中树枝晶的生长过程, 研究了来流对枝晶生长的影响. 结果表明, 来流对合金过冷熔体中三维树枝晶生长影响显著, 迎流侧枝晶尖端生长速度随来流速度的增大而增大, 枝晶尖端半径随来流速度的增大而减小; 随着来流速度的增大, 枝晶尖端选择参数减小; 在给定过冷度条件下, 随界面能各向异性的增大, 来流对枝晶尖端选择参数的影响增强; 对于给定的合金(或界面能各向异性), 来流对枝晶尖端选择参数的影响随着过冷度的增大而增强.

The dendrite morphology is determined by the interaction between the capillarity effect and the transports of heat and solute, and is significantly altered by the presence of fluid flow during solidification. A lot of numerical models have been developed to investigate the effect of fluid flow on the dendritic growth of pure materials. But up to date, only a few researches were carried out on the effect of fluid flow on the dendritic growth of alloys. The effect of fluid flow on three dimensional (3D) dendrite tip selection parameter of alloys remains an unsolved scientific problem. A 3D cellular automaton (CA) model for dendritic growth of alloys was developed in this paper. 3D CA is solved in coupling with a momentum transport model in order to predict the evolution of dendritic morphology during solidification of alloys in the presence of flow. The dendrite growth with a forced flow in an undercooled melt of an Al-4%Cu (mass fraction) alloy was simulated. The effect of forced flow on dendritic growth was investigated. The results show that a forced flow affect the three dimensional dendritic growth of an alloy significantly. The growth of the primary and secondary arm in the upstream direction is much greater than that in the downstream direction. The growth direction of the primary arm perpendicular to the flow direction tilted into the upstream direction. The dendrite tip of the primary arm perpendicular to the flow direction shows an asymmetric morphology. The degree of the tilt and the asymmetry of the tip become stronger with the increase of the forced flow velocity. With the increase of the flow velocity the growth velocity of the upstream dendrite tip increases, the radius and the selection parameter of the upstream dendrite tip decrease. For a given undercooling, the effect of forced flow on the selection parameter of the upstream dendrite tip becomes stronger with the increase of the anisotropy of the interfacial energy. For a given  alloy, the effect of forced flow on the selection parameter of the upstream dendrite tip also becomes stronger with the increase of undercooling.

为精确控制热轧780 MPa级Nb-Ti微合金化C-Mn钢中的纳米析出物(Nb, Ti)C, 利用热力模拟实验技术, 通过透射电镜观察及统计分析, 研究形变及冷却速率对纳米析出的影响规律. 结果表明, 形变可显著地提高析出物形核率, 并细化析出物平均直径; 析出物数量随冷却速率的增大逐渐减小; 既定的实验条件下, 冷却速率达到15 ℃/s可完全抑制析出物在冷却过程中形核; 随着冷却速率的增大, 析出物的形核区间由奥氏体区形核向铁素体或贝氏区转变, 析出物平均直径明显细化; 在低冷却速率条件下的变形实验钢中, 形变提高组织中的空位浓度, 促进析出物空位形核的发生; 晶界或亚晶界是过饱和空位的主要陷阱, 但空位的扩散活性很高致使低冷却速率条件下晶界或亚晶界附近的空位浓度低于析出物形核的临界形核浓度, 从而无法形核, 形成晶界附近无析出带; 无析出带宽度随冷却速率的增大而减小, 这归因于空位扩散活力随冷却速率的增大而降低.

In order to control nano-scale precipitation (Nb, Ti)C in hot-rolled 780 MPa grade C-Mn steel micro-alloyed with niobium and titanium for automobile frames, the effects of deformation and cooling rate on nano-scale precipitation were investigated by using the thermal simulation experiment technology, then through the transmission electron microscopy observation and statistical analysis. The result indicated, deformation could significantly improve density of dislocation, subgrain boundary and vacancy etc in microstructure, and promote heterogeneous nucleation of precipitation, and improve nucleation rate of precipitation and decrease the average diameter of precipitation. Deformation could improve vacancy concentration and promoted vacancy nucleation. The induction period of precipitation nucleation decrease with the increase of deformation amount and strain rate, and precipitation more easily to nucleate. Precipitation nucleation driving force was mainly supersaturation of microalloy in undeformed experimental steel, and the nucleation mechanism was mainly homogeneous nucleation. However, the nucleation mechanism was mainly heterogeneous nucleation in deformed experimental steel. In one fixed experimental deformation condition, when the cooling rate below 5℃/s, there was (Nb, Ti)C-PFZ (precipitate free zone) nearby original austenitic grain boundaries or subgrain boundaries, and the width of PFZ at cooling rate of 0.5, 1, 2 and 5℃/s were 46.9, 30.2, 28.1 and 0 nm, respectively, so the width of PFZ decreased with the cooling rate increasing. When the cooling rate reached 15℃/s, the nucleation of precipitation was totally inhibited during cooling process. The number of precipitation along with the cooling rate increases gradually decreases. With the increase of cooling rates, the nucleation zone of precipitation was transferred from austenite to ferrite or bainite, and the average diameter of precipitation was refined. Due to grain boundaries or the subgrain boundaries were main traps for supersaturated vacancy, but the diffusivity of vacancy was high, which made the vacancy concentration nearby grain boundaries or the subgrain boundaries lower than critical vacancy concentration for precipitation nucleation, so precipitate could not nucleate nearby grain boundaries or subgrain boundaries. Due to the diffusivity of vacancy was affected by temperature, when the cooling rate was slow, vacancy had enough time to diffuse and annihilate, which made wide PFZ formed. Whereas, when the cooling rate was high, the diffusivity of vacancy was reducing or disappearing, so the width of PFZ was small. In orde to ensure experimental steel had higher yield strength, austenite zone precipitation and (Nb, Ti)C-PFZ nearby boundaries should be inhabited, so the cooling rate should be more than 15 ℃/s in the practical rolling process.

进行了外加纵向静磁场下高温合金DZ417G的定向凝固实验, 考察了纵向磁场对不同尺寸试样凝固组织形貌的影响. 结果显示, 在温度梯度为70℃/cm, 抽拉速率为5 μm/s时, 施加磁场后一次枝晶间距减小, 并在试样边缘出现等轴晶组织; 随着试样尺寸的增大, 在试样边缘和中心的柱状枝晶组织遭到破坏, 形成等轴晶组织, 且出现“斑状”偏析. 这些现象可归结为磁场在固/液界面前沿合金熔体中诱发的热电磁对流(TEMC)所致.

In order to understand the influence of a longitudinal magnetic field on the microstructures of the superalloy DZ417G with different sample sizes, the superalloy DZ417G was directionally solidified under a longitudinal magnetic field. The solidification structures of the alloy with various dimensions of specimen have been investigated. The results showed that the columnar dendrites on the edge of samples were broken and changed into equiaxed dendrites in the magnetic field at the withdrawal velocity of 5 $\mu$m/s and temperature gradient of 70℃/cm. Additionally, it was found that equiaxed dendrites area expanded from the edge to the center of sample and the number of freckle-like macrosegregation increased with the size of sample. The columnar to equiaxed transition and freckle-like macrosegregation can be attributed to the thermoelectric magnetic convection (TEMC) induced by the magnetic field in the front of solid/liquid interface during directional solidification.

通过对一种新型锆钛合金在室温下的准静态压缩和不同温度下的动态压缩实验, 发现该合金在准静态和动态压缩条件下均具有良好的强度和塑性, 且随着应变速率的增加和温度的降低, 合金强度升高, 塑性下降. 基于Johnson-Cook模型, 建立了该锆钛合金动态压缩下的本构关系.

Zirconium based alloy is a new type structural material with high specific strength and good comprehensive properties. In this article, quasi-static compression at room temperature and dynamic compression under various temperatures were performed to a new zirconium-titanium alloy. It was found that this alloy showed good strength and plasticity, and the strength increased and plasticity decreased with increasing strain rate or decreasing temperature. A constitutive model under dynamic compression was established based on Johnson-Cook model, and accorded well with experimental results.