Oxidation of Steels and HgO Growth after 5000 Hours Exposure in Mercury at 573 K

 Corrosion tests on martensitic steels, F82H and MANET-II, were conducted in static Hg at 573 K in two batches: 1) the Hg covered with air for 5000 h, and 2) the Hg covered with Ar for 2000 h. Different techniques (EPMA, SEM, RHEED, XRD, SIMS) have been applied for surface analysis. The main results show that the surfaces of the samples are oxidized and covered with large amounts of red HgO single crystals (1 μm to 1 mm) under air atmosphere. The surface layers formed in the presence of air consist of oxides of types (Fe, Cr)₂O₃, Fe₃O₄, FeCr₂O₄ and have a thickness up to 680 nm for F82H and 310 nm for MANET-II. Replacing air with Ar in the containers reduces drastically the oxidation of the steels. In this case the maximum thickness of oxide film is of 10 nm and no HgO crystals form.     

高锰钢帽型样品在高速冲击下的剪切行为

绝热剪切带是材料在高速变形时一种典型的破坏形式,为了更好地理解高速冲击过程中绝热剪切带的形成和扩展,基于Johnson-Cook本构模型,利用ANSYS/LS-DYNA软件对高锰钢帽型样品高速冲击过程的剪切行为进行了二维数值模拟。结果表明:横穿剪切带方向,应力应变分布都是剪切带中心最高,然后向两边逐渐降低,类似于高斯分布; 平行于剪切带方向,应力应变分布则是呈两端高中间低的特点。然后利用模拟的应力应变场分布确定了剪切带和裂纹形成及扩展方向,即从剪切区两端形成并向中间扩展;最后通过编辑软件的k文件直接得到了剪切带内部及周围形变影响区和基体的温度分布,其和应力应变场分布规律一致,结果与实验结果基本吻合。     

激光诱导击穿光谱定量化标定谱线自动选择方法

选择合适的特征谱线是以内标法对激光诱导击穿光谱进行定量化分析的前提,需要科研工作者精心分析和比较,往往耗费大量精力和时间,而且还不能保证结果最优。基于遗传算法为内标法提出了一种从原始光谱中自动选择分析线和参考线的方法,使用该方法从低合金钢样的LIBS光谱中为锰(Mn)、镍(Ni)、铬(Cr)、硅(Si)和铁(Fe)元素分别选择了用于内标法定量分析的分析线和参考线。优选得到的最优谱线为,Mn的分析线和相应的参考元素Fe的参考线分别是403.306 8和368.745 7 nm,Si的分析线和相应的参考元素Fe的参考线分别是288.157 7和427.176 1 nm,Cr的分析线和相应的参考元素Fe的参考线分别是286.510 0和272.753 9 nm,Ni的分析线和相应的参考元素Fe的参考线分别是352.453 6和358.698 5 nm。最后基于优选得到的谱线以内标法对这些元素分别进行了定量分析,结果证明,使用这种谱线选择方法能够自动从原始光谱中找到最优特征谱线,使内标法定量分析得到最好的结果。     

直读光谱法测定合金工具钢中铬、锰和钼

建立了ARL-4460直读光谱仪对Cr12、Cr12MoV中铬、锰、钼元素的快速检测方法。使用基体铁作为内标元素,测定标准样品中铬、锰、钼元素的相对强度,减少了外界电压不稳对绝对强度稳定性的影响;由于标准样品中基体铁含量不同,为减少内标元素含量的变化对工作曲线相关系数和估计标准差的影响,使用相对含量校正工作曲线。在优化的实验条件下,试样中三种元素的相对标准偏差分别为0.68%、0.79%和1.7%(n=11)。测定结果与化学分析方法测定结果一致,可实现合金工具钢中铬、锰和钼的快速检测。     

Electrochemical Behavior of Stainless Steels for Sudomotor Dysfunction Applications

AISI 304L is used in Sudoscan^TM technology (Impeto Medical Inc.) for the early diagnosis of small fiber neuropathy caused by type‐2 diabetes or cystic fibrosis. In a recent paper, several substitute electrodes were analyzed, among which the biocompatible nickel‐free AISI 430 appeared as an interesting material. In the present work, we compare in details the electrochemical behavior of AISI 430 with respect to the reference AISI 304L, using Electrochemical Impedance Spectroscopy (EIS) in mimetic electrolytic solutions of sweat. Apart of being cheaper than AISI 304L, AISI 430 has roughly similar characteristics but is slightly more sensitive to chloride ions concentration and, according to EIS and SEM analyses, forms a thicker, more homogeneous and protective oxide layer, which makes it a convenient electrode material.     

On the modified grain-size-distribution method to evaluate the dynamic recrystallisation fraction in AISI 304 stainless steel

The purpose of the present work was to verify the grain size distribution (GSD) method, which was recently proposed by one of the present authors as a method for evaluating the fraction of dynamic recrystallisation (DRX) in a microalloyed medium carbon steel. To verify the GSD-method, we have selected a 304 stainless steel as a model system and have measured the evolution of the overall grain size distribution (including both the recrystallised and unrecrystallised grains) during hot compression at 1,000 °C in a Gleeble machine; the DRX fraction estimated using the GSD method is compared with the experimentally measured value via EBSD. The results show that the previous GSD method tends to overestimate the DRX fraction due to the utilisation of a plain lognormal distribution function (LDF). To overcome this shortcoming, we propose a modified GSD-method wherein an area-weighted LDF, in place of a plain LDF, is employed to model the evolution of GSD during hot deformation. Direct measurement of the DRX fraction using EBSD confirms that the modified GSD-method provides a reliable method for evaluating the DRX fraction from the experimentally measured GSDs. Reasonable agreement between the DRX fraction and softening fraction suggests that the Kocks-Mecking method utilising the Voce equation can be satisfactorily used to model the work hardening and dynamic recovery behaviour of steels during hot deformation.     

On primary damage and secondary electron damage in heavy ion tracks in plastics

Despite many successful applications of non-photographic dielectric track detectors in numerous scientific and technological fields, the basic mechanisms of track formation and development are still rather unknown for these detectors. In this paper an attempt is made to estimate the relative importance for track formation in plastics of direct interactions of heavy charged particles and of events of their secondary electrons. Both classes of events are weighted rather differently in existent track formation models. The discussion is mainly based on results obtained from calculations on the spatial distribution of events along and around the paths of fast ions and of electrons.     

时效处理温度对17-4PH铸造不锈钢在稀硫酸料浆中的冲刷腐蚀性能影响

采用自制料浆罐式冲刷腐蚀试验机研究了在含固相颗粒稀硫酸料浆介质中,时效处理温度对17-4PH铸造不锈钢的组织、硬度及冲刷腐蚀性能的影响,分析了不同时效温度下冲击速度对17-4PH铸造不锈钢冲刷腐蚀行为的影响,观察了冲刷腐蚀表面形貌,探讨了冲刷腐蚀机理.结果表明:17-4PH铸造不锈钢经固溶处理及460℃左右时效处理后其硬度达到最大值;经时效处理后17-4PH铸造不锈钢冲刷腐蚀特征表现为纯冲刷磨损为主,腐蚀为辅,腐蚀促进磨损;在冲刷速度较低时,时效处理温度对17-4铸造不锈钢的冲刷腐蚀率影响不大,而在冲刷速度较高时,460℃左右时效处理后,由于析出大量细小弥散分布的ε-Cu沉淀相而具有最佳的沉淀强化效果,抗冲蚀腐蚀性能最佳;在不降低耐腐蚀性能的前提下,利用沉淀析出硬化是一种提高材料抗冲刷腐蚀性能的有效方法.     

Computational design of UHS maraging stainless steels incorporating composition as well as austenitisation and ageing temperatures as optimisation parameters

An extended integral alloy design approach for the development of new ultra high strength maraging steels is presented, which incorporates not only chemical composition effects but also criteria accounting for the influence of the entire heat treatment. The approach considers the desired strengthening precipitates formed during the final ageing treatment as well as undesirable equilibrium phases present during the preceding high temperature homogenisation treatment. The results are compared with the predictions of a previous model, which considered the combination of composition and final precipitation tempering stage only.