制样方法对IF钢纳米压入测试结果的影响

 对3种不同方法制备的IF钢试样进行了纳米压入表征,分析了制样方法对IF钢中铁素体纳米压入测试结果的影响。结果表明,制样方法对铁素体杨氏模量平均值影响不大,但对硬度平均值影响显著,机械抛光和机械抛光+化学侵蚀状态铁素体的硬度均高于机械抛光+电解抛光状态的铁素体。这主要是因为机械抛光对试样表面造成了明显的加工硬化层,而化学侵蚀处理不能完全去除硬化层,只有电解抛光才能起到有效消除硬化层的作用。机械抛光+电解抛光处理更有利于IF钢的纳米压入表征。     

钢铁材料EBSD样品制备工艺研究

以X80管线钢和SWRH82B高碳钢两种样品为例,利用机械抛光、化学抛光、电解抛光及聚焦离子束原位加工等方法进行了钢铁材料EBSD样品制备研究,并分析了4种制备方法的优缺点.     

钛合金材料OIM试样的电解抛光及制备工艺

由于钛合金材料强度硬度较高，机械抛光通常不能去除试样表面的残余应变层，因而采用电解抛光是制备电子背散射衍射试样的理想方法。本研究通过正交试验进行优选，并对优选的电解抛光工艺参数进行调整，制定出了钛合金电子背散射衍射试样的快速制备工艺。     

CdTe基底表面的STM研究

用扫描遂穿显微镜(STM)研究了用于 MBE 生长的 CdTe 基底表面,发现其表面不平整度取决于不同的表面制备步骤。机械抛光试样的表面粗糙度大约为100nm,这是由抛光粉决定的。用化学-机械抛光法制备的样品表面粗糙度下降至60nm。经腐蚀抛光后的     

SLM打印成形CoCrMo合金牙冠的表面粗糙度和硬度优化

为了改善选区激光熔化打印成形的CoCrMo合金牙冠的表面粗糙度和硬度,提高其与人体的适配性,分别采用了电解抛光和固溶处理方法对牙冠进行改善处理。测试了经不同电解液和电解参数抛光后的牙冠表面粗糙度以及经不同工艺固溶处理后牙冠的硬度,利用三维轮廓仪观察了抛光前后表面形貌,利用金相显微镜和扫描电子显微镜观察了微观组织。结果表明,SLM制备的CoCrMo合金牙冠在HNO_3+H_3PO_4体系电解液中抛光效果最佳,牙冠表面粗糙度较电解抛光前降低达70%以上;牙冠经1 503K固溶10h后,显微硬度可由固溶前的470HV降至350HV,与人体天然牙齿硬度相当。SLM制备的CoCrMo牙冠综合性能得到了显著的改善。     

钨铜合金表面粗糙度对抗电弧烧蚀性能的影响

将纯W、纯Cu和W70Cu30合金分别进行机械磨光、电解抛光和机械抛光后获得3种不同的表面状态,在专有设备上模拟电触头材料的电弧烧蚀过程,通过扫描电子显微镜观察首击穿烧蚀形貌。结果表明:通过机械抛光获得的表面粗糙度最小,对于W70Cu30合金可达到0.044μm,电解抛光次之,机械磨光最大;随表面粗糙度降低,W70Cu30合金的击穿场强逐渐增大,烧蚀区域趋于规整化,烧蚀产物增加,烧蚀坑的分布更加集中,纯W、纯Cu也表现出相同的现象;在本实验条件下材料表面粗糙度在0.2~0.3μm时,其抗电弧烧蚀性能最好。     

镜面白钼丝电解技术探讨

研究了通过电解抛光制备镜面白钼丝的工艺技术。对电解方式及电解参数、电解介质及电极材料、高温退火进行实验研究。结果表明,采用钼丝与阳极直接接触,硫酸电解液作为介质,通过直流电解可生产出表面粗糙度Ra达0.2的镜面白钼丝。将白钼丝进行高温退火以钝化、抛光表面,不仅能提高白钼丝表面抗氧化能力,还能调节其物理性能指标。     

纯钛的电解抛光方法

纯钛制金相样时,因为太软,易产生轻微的划痕,用一般的机械抛光方法效果不佳,而采用电解抛光方法效果良好。然而,电解抛光需要找到合适的电解液及工艺参数,特别是要找到一恒流区作为抛光工作区域,高于恒流区的上限,由于放出氧气形成气泡,打碎了抛光膜,会引起严重的点蚀,     

医用镍钛合金的电解抛光进展

随着市场对金属材料的粗糙度、光泽度以及耐腐蚀性能的要求逐渐提高,电解抛光技术作为精密表面加工技术,由于具有效率高、处理试样表面光滑、能够保持材料原有性能等特点,在表面处理领域得以迅速发展.介绍了目前业界比较流行的三类电解抛光液体系:酸-酸体系、酸-醇体系和醇-盐体系以及其主要成分,分析了在不同电解抛光液体系成分下电解抛光液浓度、抛光温度和抛光电压等条件的改变对抛光效果(粗糙度、耐腐蚀)以及抛光效率的影响,进一步比较了不同电解抛光液体系的优缺点,并综述了电解抛光原理机制及其技术的新发展.     

哈氏合金表面粗糙度AFM测量中扫描尺度等问题研究

哈氏合金Hastelloy C276是一种被广泛应用的镍基合金,具有机械性能优良、抗腐蚀能力强等优势,在第二代高温超导导线的离子束辅助沉积(IBAD)技术路线中被用作金属基底,因此其表面抛光与粗糙度测量受到了广泛重视。哈氏合金的表面形貌和粗糙度测量一般采用原子力显微镜(AFM)方法,在该方法中扫描尺度对测量结果具有显著的影响。本研究对两个分别进行了电化学抛光和机械抛光的哈氏合金带材短样,在1~70μm范围内选取不同扫描尺度进行了AFM测量,从而对其表面形貌获得了全面的了解,并发现其表面粗糙度随着扫描尺度的变大出现了明显的增大,文中还在不同扫描尺度下考察了电化学抛光与机械抛光的作用区别。此外,本研究中分析了AFM图像的后处理中flatten阶数的影响,对从AFM图像中分割出小尺度局域计算粗糙度的方法进行了改进,并讨论了AFM测量粗糙度的可重复性问题。通过这些研究,对表面粗糙度的AFM测量方法在全面性和有效性方面进行了完善,提出了粗糙度描述时有必要给出的相关参数。     

Statistical Quantification of the Impact of Surface Preparation on Yield Point Phenomena in Nickel

Nanoindentation was used to evaluate the effect of three surface preparation techniques—mechanical polishing, electropolishing, and ion polishing—on experimental measurements of incipient plasticity in commercially pure Ni 200. Surface preparation techniques are linked to defect densities, estimated with image quality (IQ) and kernel average misorientation (KAM) data obtained from electron backscatter diffraction patterns and the Taylor relation. Minimum yield pressures are insensitive to surface preparation, while mean yield pressure depends on dislocation density, and the maximum yield pressure is likely influenced by defects other than dislocations. KAM coupled with IQ may be a useful non-destructive parameter to relate surface defect density to the resulting changes in the spatial variability of incipient plasticity during a nanoindentation experiment. This analysis makes the assumption that geometrically necessary dislocation density is proportional to total dislocation density; in cases where this condition is not satisfied, the KAM analysis may not be valid.     

Effects of Nanometer Carbon Black on Performance of Low-Carbon MgO-C Composites

The low-carbon magnesia-carbon(MgO-C)composites containing 3%(mass fraction,the same below)carbon were prepared by adding various types of carbon black(CB).The mechanical properties,oxidation resistance at 1100 ℃ in oxidizing atmosphere,and thermal shock resistance after 5 times dipping in 1600 ℃ molten steel of the low-carbon composite samples were investigated,compared with a commercial high-carbon MgO-C composite containing carbon of 16%.The results show that the mechanical properties,oxidation resistance and thermal shock resistance of the low-carbon samples are improved with the decrease of CB particle size.Thermal shock resistance of the low-carbon sample containing nanometer CB N220 is obviously better than that of other low-carbon samples,and reaches the level of the high-carbon samples.     

Ti2AlNb合金金相试样的制备方法

介绍了Ti2AlNb合金金相试样的制备方法,并描述了试样制备过程中研磨、抛光、浸蚀的技巧和辅材的选择方法。实验结果表明：在抛光过程中采用短绒毛的平绒织物和超细纤维眼镜布,并配合使用合适粒度的加有洗洁精的Cr2O3,抛光液进行粗抛和精抛,可快速制备高质量的金相试样;采用合适浓度的化学腐蚀液氢氟酸＋硝酸或氢氟酸＋过氧化氢溶液进行浸蚀后,可获得晶界轮廓清晰的加工态组织（口单相组织）或清晰的热处理组织（晶内的网篮组织和魏氏组织）。     

Engulfment Behavior of Inclusions in High-Carbon Steel: Theoretical and Experimental Investigation

Previous studies on inclusions behavior at the front of the solidifying steel shell have mainly focused on low-carbon steels. However, with the increasing applications of high-carbon steel in recent years because of its superior properties, it is crucial to understand this behavior in high-carbon steel. Most of the high-carbon steels are deoxidized by silicon, calcium treated, and contain higher sulfur percentage. Also, higher carbon content has a determining influence on the viscosity and surface tension, which will affect the inclusion behavior. In this study, we have investigated the engulfment behaviors of inclusions in front of the solidifying interface in high-carbon steels using concentric solidification method. The critical velocity of the growing shell, at which the particle is engulfed in the solidifying shell, instead of being pushed by this shell, was determined. The inclusion identified in this study is a bi-component form of CaO-SiO₂-based oxide and CaS. It was revealed that engulfment behavior is strongly affected by convection of liquid steel that originates from carbon push out in high-carbon steels. This study provides new crucial information to produce high-carbon steel with fewer inclusions, which opens new application pathways for this emerging grade of steel.     

Improving the quality of high and low-carbon steel rods employed in wire drawing operations

High and low tensile strength as well as high ductility are required for both, high and low-carbon steel rods which are to be further processed in wire drawing operations. In addition to chemical composition, suitable cooling rates are important for the control of mechanical properties, as far as the Stelmor process is concerned. In this investigation, heat transfer models are coupled with the kinetics of austenite transformation into pearlite and ferrite-pearlite, respectively, in order to understand the link between the Stelmor process parameters and the final quality of low and high-carbon steel rods. In applying these models a considerable difference occurred in the mechanical properties of high-carbon rod samples taken from the loop edge of the Stelmor conveyor and those taken from the loop center. The latter showed higher tensile strengths, furthermore, the difference to the lower-strength samples increased with low conveyor speeds. Most homogeneous mechanical properties were found for a conveyor speed of 0.4 m/s. In the case of low-carbon steels, low nitrogen contents during steelmaking and a slow and controlled cooling in the Stelmor process were found to be the most important factors regarding mechanical properties. The conclusions of this investigations are actually being applied to production so as to obtain a better quality of steel rod semies.     

钢铁材料金相样品研磨过程中的缺陷分析与控制

钢铁材料金相样品制备需经过一系列的研磨过程,获得镜面状的表面以备金相检验用。分析了在研磨过程中由于操作不当产生各种缺陷的原因。阐述了为消除这些缺陷在磨制、抛光过程应遵循的一般性原则。     

Indentation Size Effect (ISE) in Copper Subjected to Severe Plastic Deformation (SPD)

The characteristic length scale of deformation in copper specimens subjected to severe plastic deformation (SPD) through surface mechanical attrition treatment (SMAT) was studied with indentation experiments. Annealed copper disks were shot peened with 6-mm diameter tungsten carbide spheres with an average velocity of 2.3 m/s for 15 minutes in a vibrating chamber. The SMAT-treated specimens were cross-sectioned, and the exposed face was studied under nanoindentation in order to determine the effect of dislocation density on surface hardness and indentation size effect (ISE). Since the specimen preparation of the exposed face involved mechanical polishing, which in turn introduced additional SPD on the indenting face, the effect of mechanical polishing on hardness measurement was investigated first. To this end, the mechanically polished specimens were subjected to various durations of electrochemical polishing. Hardness measurements on these specimens showed that the effect of mechanical polishing was substantial for both microindentation and nanoindentation, the impact being significantly larger for nanoindentation. Consequently, the measured depth of influence of the SMAT process, determined on specimens subjected to longer durations of electrochemical polishing, shows larger values compared to those previously reported in the literature. The ISE shows a bilinear relationship between the square of hardness and the reciprocal of indentation depth. The slope of this behavior, corresponding to smaller indentation loads, which is a measure of the ISE associated with a strain gradient, shows a power-law relationship with an increase in the distance away from the SMAT surface, instead of the constant value expected with the Nix–Gao type model.     

Effect of Microstructure and Surficial Oxidation on the Wear Behavior of an UNS S41003 Stainless Steel

The UNS S41003 ferritic stainless steel is a low-carbon alloy that has great corrosion and oxidation performances in wet and aqueous environments, as well as it has high mechanical strength and ductility when compared to the most ordinary low-carbon steels. These great characteristics, allied to its relatively low manufacturing cost, have made it a potential option to replace structural steels in many applications. Although it is a current trend, there are still few published studies that relate this steel manufacturing process with microstructural evolution and mechanical behavior, mainly regarding its wear behavior, which is a substantial and sometimes limiting characteristic for its applications. In this context, this article presents a pioneering study about the use of biphasic microstructures (ferrite–martensite) and controlled surficial oxidation to enrich the wear behavior of a UNS S41003 steel type. This study concludes that, if well planned, both the increase of martensite fraction and the controlled growth of an adherent and compact oxide layer on the steel surface significantly improve its wear performance, decreasing its wear rate up to 93%.