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运用高能喷丸技术实现了工业纯铁表面自纳米化,利用电子背散射衍射(ElectronBackscatteredDiffraction,EBSD)对自纳米化组织的结构特征进行了分析,在此基础上探讨了工业纯铁自纳米化机理。结果表明,工业纯铁自纳米化组织由三个典型区域组成,分别含有大量残存住错,大角度晶界及大量小角度晶界。自纳米化组织含有再结晶织构和形变织构,但由于晶粒取向差不同,变形难易程度不同导致两种织构的比例不同。位错运动、晶粒取向差不同导致变形不同步及发生再结晶是工业纯铁表面自纳米化过程中晶粒细化的主要原因。 相似文献
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综述了金属材料表面自纳米化技术的研究现状。表面机械加工自纳米化的原理是在一定的应力作用下,使金属材料表面层产生剧烈的塑性变形,导致晶粒细化。晶粒的细化机理主要取决于金属材料的晶格结构和层错能;表面自纳米化能显著提高金属材料的综合性能。展望了表面自纳米化技术的发展前景。 相似文献
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文章综述了材料表面自纳米化的国内外研究现状,包括表面自纳米化的制备方法、基本原理、表层结构及机理、性能研究,展望了表面自纳米化技术的发展前景及目前有待解决的问题。 相似文献
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Laser surface alloying of iron substrate with copper under different processing conditions has been systematically studied. The microstructural analysis reveals a predominantly cellular microstructure with copper wetting the cell boundaries. Globular distribution of copper at higher laser scanning speeds can be observed occasionally indicating the system under these conditions to be near the metastable miscibility gap. The concentration of copper in the pool is related to the laser scanning speed. In all cases a banded morphology indicating unsteady growth towards the bottom of the alloyed zone is observed. The hardness of the alloyed zone is significantly higher and is attributed to work hardening due to differential thermal contraction of the two phases in the alloyed zone. 相似文献
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In this research, the effect of austenitic stainless steel cladding on improving the wear behavior of ductile iron was studied. Samples made of ductile iron were coated with steel electrodes (E309L) by manual shielded metal arc welding. The effect of coated layer thickness on microstructure, hardness, and wear resistance of the surface were investigated. Wear resistance of the samples was measured using the pin-on-plate technique. Optical microscopy and scanning electron microscopy were used to investigate microstructure and wear mechanisms. The phases in the interface of both the coating and the substrate were studied by X-ray diffraction. The results showed that a film of white chromium-enriched iron formed at the interface between the substrate and coating which contained iron–chromium complex carbides. It was, therefore, concluded that enhanced properties would be obtained if the coating thickness and the carbides deposited on the surface were reduced. In samples with a thin coating, surface hardness rose to above 1150 HV (five times higher than that of the substrate) and wear resistance increased significantly. 相似文献
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A niobium modified layer on a pure titanium surface was obtained by means of a double-glow plasma surface alloying technique. Microstructure and phases resident in the alloy layer were analyzed. The processing parameters and effects of cathode sputtering before the diffusion process were also studied. The results show that the surface niobium content in the modified layer is similar to that in the Ti-45Nb alloy, and decreases gradually from the surface into the underlying substrate. The oxidation behavior of the modified pure titanium at 900 °C was noticeably improved after the niobium alloying process. Characterization was performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The oxidation mechanism is also discussed. 相似文献
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The double-glow surface alloying technique, also called the Xu-Tec/Xu-Loy process, is a novel technique in the field of surface alloying. This technique allows alloy layers with unique physical, chemical and mechanical properties, such as nickel-based alloy layers, stainless-steel layers and age-hardened surface high-speed steel layers to be formed at the surface of treated metallic materials. In this paper, recent research of the application of the double-glow plasma surface alloying technique in the formation of corrosion resistance alloy layers is briefly reviewed. The results of a study of Ni-Cr-Mo-Nb and Ni-Cr-Mo-Cu corrosion-resistant alloying layers as well as composite alloying layers with an electric brush plating Ni interlayer are reported. 相似文献
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Double Langmuir probe technique was used for plasma diagnostics of discharge process in double-glow plasma alloying furnace. Investigated that the effect of changes of voltage of the source pole and air pressure on plasma parameters. Results show that plasma density increases, electron temperature decreases and potential of the probe decreases, with the rise of voltage of the source pole under condition of fixed cathode potential and fixed air pressure. During increasing of air pressure in furnace, electron temperature decreases and probe potential increases. The change of probe potential is smart at start of the measuring and probe potential goes to stabilization only when degas process goes to finishing. 相似文献
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Effects of alloying elements on the electrochemical characteristics of iron aluminides in the H2SO4, H2SO4+KSCN and HCl solutions
were investigated using electrochemical tests. The corrosion morphologies in iron aluminides were analysed by utilising optical
microscopy. It was found that the addition of Cr and Mo to iron aluminides increased the corrosion potential, pitting potential
and repassivation potential. The active current density, passive current density and reactivation current density decreased
as Cr and Mo were added. In the case of Mo addition, the passive current density was slightly higher in the H2SO4 solution
than in solutions containing SCN- and Cl-. When B was added to samples, the corrosion potential and repassivation potential
decreased, whereas the active current density, passive current density, reactivation current density and pitting potential
increased. Iron aluminides containing Mo and Cr showed remarkably improved intergranular and pitting corrosion resistance
to SCN- and Cl- solution. On the other hand, B addition accelerated granular and intergranular corrosion by precipitation
of borides.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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《Materials Science & Technology》2013,29(11):1310-1316
AbstractA study of electric contact surface treatment to ductile iron has been carried out. This technology was based on the application of the contact resistance heating between the electrode and workpiece. For comparison, the experiments of induction hardening to ductile iron were studied. The microstructure, microhardness, surface residual stress and wear properties were investigated using optical microscope, scanning electron microscope, X-ray diffraction, Vickers microhardness and rolling contact wear tests. Electric contact surface treatment resulted in the formation of fine ledeburite (white bright layer) and martensite in the ductile iron surface, in which the hardness in these areas was higher than that of induction hardened surface. The wear test results showed that the ductile iron surface after electric contact surface treatment had better wear resistance owing to the fine microstructure, high hardness and residual compressive stress. 相似文献