0Cr15Ni75Fe合金热处理制度对组织性能的影响

本文通过对0Cr15Ni75Fe管材进行不同的固溶处理，总结出该钢热处理制度对其组织性能的影响规律，并制定出适合该钢的最佳热处理制度。     

合金元素Cr,Al对Sn-Ag-Cu基无铅钎料高温抗氧化和润湿性的影响

研究了少量合金元素Cr，Al对Sn-3．0Ag-0．5Cu（305）无铅钎料高温抗氧化性的影响。钎料在液态下的表面颜色变化以及热重分析表明，Cr，Al能明显改善305合金钎料的抗氧化性能。通过合金元素Cr，AI的抗氧化机制和X射线衍射分析得出：Al和Cr在钎料表面形成致密氧化膜，形成“阻挡层”，抑制了钎料的氧化。同时也比较了合金元素Cr，Al对305钎料润湿性能的影响，结果表明：单独加Al不利于钎料的铺展，少量的Cr和Al同时加入对钎料的铺展没有太大的影响。实验证实：Cr和Al的共同作用明显提高了Sn-3．0Ag-0．5Cu钎料的高温抗氧化性，同时对钎料的润湿性也没有恶化作用。     

High-Temperature Oxidation Behavior of 5Cr21Mn9Ni4N Steel Micro-Alloyed by Rare Earth

The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.     

High-Temperature Oxidation and Oxide Scale Formation in Plasma-Sprayed CoNiCrAlYRe Coatings

MCrAlY coatings are usually adopted to improve the environmental resistance of Ni-based superalloy components of turbine engines against high-temperature oxidation and hot corrosion. In this work, CoNiCrAlYRe coatings were produced by atmospheric plasma spraying. The coatings exhibited relatively low oxygen content and porosity. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that the high-temperature exposure at 1383 K (1110 °C) promoted the growth of an oxide scale on the top surface being composed of a continuous and dense Al₂O₃ inner layer followed by an outer mixed layer (Cr₂O₃ and spinels). The oxide scale was mainly composed of Al₂O₃, while the formation of mixed oxides occurred at lesser extent. After high-temperature exposure, the formation of internal oxides in some areas reduced the inter-lamellar cohesion, so that a decrease in microhardness was found.     

Mass-spectrometric determination of activities in Fe−Cr and Fe−Cr−Ni alloys

The Knudsen cell-mass spectrometer combination has been used to study the Fe?Cr system and some Fe?Cr?Ni liquid alloys. The Fe?Cr liquid alloys at 1600°C are found to be essentially ideal when referred to pure liquids as standard states. Phase equilibria over a limited composition range for this system are derived from the behavior of the ion-current ratios. The necessary equations are derived to apply the integration technique to the measured ion current ratios in a ternary system and the method is applied to the Fe?Cr?Ni system at 1600°C. The results are represented, within experimental error, by the following equations: forN _Fe≥0.6, $$\begin{gathered} ln \gamma _{Fe} = - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.26 - 0.08(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$ forN _Fe=0.45, $$\begin{gathered} \ln \gamma _{Fe} = - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.19 - 0.20(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$      

Characterization and High-Temperature Oxidation Behavior of Cold-Sprayed Ni-20Cr and Ni-50Cr Coatings on Boiler Steels

Microstructure and mechanical properties of cold-spray coatings are usually required in order to explore the potential industrial application of the latter. This article demonstrates the successful formulation of Ni-20Cr and Ni-50Cr coatings on two boiler steels, namely, SAE 213-T22 and SA 516 steel by cold-spray process. The microstructure, coating thickness, phase formation, and microhardness properties of the coatings were evaluated. The coatings were subjected to cyclic heating and cooling cycles at an elevated temperature of 1173.15 K (900 °C) to ascertain their high-temperature oxidation behavior. Moreover, these cyclic exposures can give useful information regarding the adhesion of the coatings with the substrate steels. Of all the coatings, the Ni-50Cr coating on SA 516 steel had a maximum average hardness value of 469 Hv. As observed from the surface field emission–scanning electron microscopy (FE-SEM) analysis, the coatings were found to have nearly dense microstructure with the sprayed particles in interlocked positions. It was concluded that the cold-spray process is suitable for spraying the preceding powders onto the given boiler steels to produce nearly dense and low oxide coatings. The coatings, in general, were found to follow the parabolic rate of oxidation and were successful in maintaining their surface contact with their respective substrate steels.     

Effect of titanium on the nitrogen solubility in complex liquid Fe−Cr−Ni alloys

The effects of dilute additions of titanium up to 0.20 wt pct on the solubility of nitrogen in two complex Fe−Cr−Ni alloys were examined over the temperature range 1450 to 1600°C. Sieverts' law was obeyed by all titanium-bearing alloys up to some nitrogen pressure below one atmosphere. ‘Breaks’ in each solubility plot were observed that corresponded to the formation of titanium nitride. Titanium additions were observed to lower the nitrogen solubility in each group of alloys. This effect is opposite to that previously observed in pure iron. Calculated values of the solubility product (pct Ti) (pct N) for TiN formation in each alloy increased with rising melt temperature.     

Ultrahigh-Temperature HfB2-Based Ceramics: Structure,High-Temperature Strength,and Oxidation Resistance

Powder Metallurgy and Metal Ceramics - Ultrahigh-temperature hafnium diboride ceramics with additions of 15 vol.% MoSi2 or 15 vol.% SiC or a combined addition of 15 vol.% SiC and 5 vol.% WC were...     

The Effect of Nb Addition on the Microstructure and the High-Temperature Strength of Fe3Al Aluminide

Metallurgical and Materials Transactions A - The microstructural and high-temperature mechanical properties of Fe–26Al–xNb (x = 3 and 5 at. pct) are...     

The precipitation of Ni3Nb phases in a Ni−Fe−Cr−Nb alloy

The age hardening of a Ni?Fe?Cr?Nb alloy containing 4.85 wt pct Nb has been studied using transmission electron microscopy. The major hardening phase in this alloy isγ*, DO₂₂-ordered Ni₃Nb, which precipitates as a fine dispersion of square plates. It is shown that nucleation ofγ* plates may be dependent upon matrix excess vacancy concentration, but nucleation ofγ* plates is also observed at dislocations and extrinsic stacking faults. Theγ* phase is metastable with respect to the orthorhombic Ni₃Nb phase, β, which precipitates by either a cellular or an intragranular reaction, depending upon the aging temperature. It is proposed that the intragranular nucleation of β laths proceeds by the growth of stacking faults from withinγ* plates; theγ* plates subsequently dissolve in favor of the β laths. Room temperature deformation of theγ* dispersion is shown to produce faults within theγ* plates; possible dislocation reactions occurring during this deformation are discussed.     

超细(W, Ni, Fe)复合氧化物粉末制备工艺的研究

研究并探讨了喷雾干燥法制备超细(W，Ni，Fe)复合氧化物粉末的工艺原理，实验中分别采用了浓度为40％及15％的(W，Ni，Fe)混合盐溶液，结合离心式喷雾干燥法考察了制备复合氧化物粉末的影响因素；采用SEM观察了颗粒形貌，并用XRD及DELSA 440SX Analyzer Control粒度分析仅分别测试了晶粒度大小和颗粒粒度分布。结果表明：粉末呈球形，粉末颗粒由平均54nm的晶粒团聚而成，粉末粒度分布在200-300nm之间。并分析了料液浓度、转速、进料量、温度、料液表面张力和粘度分别对粉末粒度的影响。结合实验过程讨论了离心式喷雾干燥法的3种雾化机制：料液直接分裂成液滴、丝状割裂成液滴和膜状分裂成液滴。     

AgCu_4Ni_(0.3)合金的内氧化动力学、组织结构和性能的研究

内氧化Ag基合金由于具有优良的导电性和导热性而成为一种重要的电接触材料。利用X射线衍射仪(XRD)、光学显微镜(OM)和显微硬度仪对AgCu4Ni0.3合金在大气条件下,700℃时的内氧化行为、组织结构以及性能进行研究,并从热力学和动力学的角度对合金的内氧化机制进行了分析。研究结果表明,在700℃氧化8.5 h后,AgCu4Ni0.3合金的氧化层主要由CuO以及NiO所组成,并没有明显的Ag的氧化物形成。Cu,Ni元素在合金中发生了明显的选择性氧化。横截面形貌表明厚度为0.8 mm的AgCu4Ni0.3合金在大气退火8.5 h后已完全氧化,CuO和NiO颗粒均匀弥散分布于氧化层基体中。内氧化后合金的硬度值(HV)高达126,远高于退火态初始合金的硬度。综上结果表明AgCu4Ni0.3合金在大气条件下的内氧化是可行的,且其内氧化动力学符合抛物线规律。这与AgCuNi合金的内氧化热力学计算结果完全一致,为AgCuNi合金的内氧化生产提供了可靠的理论和实验依据。     

Alloy powders in the Fe—Cu, Fe—Cr, Fe—Mn, and Fe—Cr—Mn systems

Studies have been done on iron-copper, iron-chromium, iron-manganese, and iron-chromium-manganese powder alloys, which have been made by dispersing the melts with high-pressure nitrogen. The use of such alloys in the preparation of low-alloy construction materials eases the stringent specifications for the oxidation potential of the controlled gas medium, and it also produces a more uniform distribution of the alloying elements in the sintered material.     

降低钠还原钽粉中铁、镍、铬杂质含量的研究

对降低氟钽酸钾钠还原钽粉中铁、镍、铬杂质含量进行了研究,结果表明：降低钽粉中铁、镍、铬含量的最根本办法是在液－液钠还原过程中减少熔盐对还原设备的腐蚀,选择合适的熔盐体系及组成、降低还原起始温度以及以一定钠与稀释剂在反应罐中熔融,然后再加氟钽酸钾并使之熔融的操作方法等,均可使钽粉中的铁、镍、铬含量明显减少。     

Effect of Grain Boundaries and Grain Orientation on Structure and Properties

The evolution of deformation microstructures in metals follows a universal pattern of grain subdivision. However, the structure in the grain boundary region may be different from that in the grain interior, although a characteristic region cannot be identified for polycrystals with medium to high stacking fault energy. In the grain interior, the dislocation structure is predominantly composed of almost planar boundaries (geometrically necessary boundaries) and cell boundaries (incidental dislocation boundaries) forming a cell block structure. For grains with grain sizes reaching down to about 4 μm deformed in tension and by rolling, a clear correlation has been established between the characteristics of the deformation structure and the orientation of the grain in which it evolves. A similar correlation is observed for single crystals of different orientations. Such correlations form the basis for a general analysis of active slip systems and for modeling of the flow stress and flow stress anisotropy of polycrystalline samples.