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1.
稀土对高铬铸铁碳化物形态及相变动力学的影响   总被引:6,自引:0,他引:6  
研究了稀土元素对高铬铸铁中碳化物的影响,并对加稀土、不加稀土的高铬铸铁试样的连续冷却转变(CCT)曲线进行了测定。结果表明,稀土元素能破碎高铬铸铁中的碳化物,使碳化物由网状、长条状向岛状、块状过渡。同时,稀土元素提高了高铬铸铁的固态相变温度并缩短了贝氏体的孕育期。  相似文献   

2.
稀土对莱氏体钢共晶碳化物粒化的影响   总被引:6,自引:2,他引:4  
研究了稀土对莱氏体钢中共晶碳化物热处理粒化的影响,探讨了稀土元素的作用机制。结果表明:稀土细化了莱氏钢中奥氏体晶粒和共晶碳化物,使离异共晶数量增多,减少了Cr、Mo合金元素偏析,并使M7C3(M=Fe、Cr)碳化物中孪晶等晶格缺陷增多,从而降低碳化物的稳定性,促进了共晶碳化物的粒化动力学过程,得到良好的粒化效果。  相似文献   

3.
稀土对9Cr2Mo钢抗热冲击性能的影响   总被引:5,自引:5,他引:0  
利用X射线衍射仪和金相方法研究了稀土元素对9Cr2Mo冷轧辊钢抗热冲击性能的影响,试验结果表明,稀土元素抑制了热影响区回火时碳化物的析出,从而提高了9Cr-2Mo钢热冲击性能。  相似文献   

4.
稀土对白口铸铁中碳化物形貌及冲击疲劳的影响   总被引:4,自引:2,他引:2  
利用高温度梯度的区熔定向凝固装置和冲击疲劳试验机,研究了稀土元素对低铬白口铸铁中碳化物形貌及冲击疲劳性能的影响。实验结果表明,稀土元素对M3C型碳化物有很强的变质作用,它可使板状炭化转变成板条状和杆状。稀土元素含量愈高,转变量愈多。稀土变质处理可有效地提高低铬白口铸铁的冲击疲劳抗力,降低裂纹扩展速率,推迟裂纹产生的时间。随稀土含量增加,冲击疲劳抗力大幅度增加,裂纹扩展速率成倍下降。  相似文献   

5.
研究了稀土元素对热轧辊钢60CrMnMo高温低周疲劳循环特性的影响,同时对热疲劳前后的试样硬度进行了比较,试验结果:稀土元素可明显抑制60CrMnMo钢疲劳过程中的循环软化,并细化了回火过程中碳化物颗粒,阻碍了热循环过程中碳化物颗粒的聚焦、长大。  相似文献   

6.
稀土元素对低铬半钢热疲劳性能的影响   总被引:1,自引:0,他引:1  
研究了稀土元素对低铬半钢铸态及经热处理后组织中的共晶碳化物形状的影响,在此基础上着重研究了该材料的热疲劳性能。结果表明:稀土元素能改善共晶碳化物的形状,抑制热疲劳裂纹的萌生与扩展,提高其热疲劳性能,尤其稀土变质后再经热处理后效果更明显。当试样经0.20%(质量分数)稀土变质后经950℃,3h正火处理时,热疲劳性能最佳。  相似文献   

7.
Ni-Mn-Ga-RE(RE=Tb,Sm)合金的马氏体相变和磁感生应变   总被引:1,自引:1,他引:0  
研究了Ni48Mn33Ga19合金添加微量稀土元素Tb和Sm后,对合金的马氏体相变、磁感生应变及机械抗弯性能的影响。结果发现,微量稀土元素Tb和Sm的掺人,降低了合金的马氏体相变温度和居里温度,但晶粒显著细化,使合金的抗弯强度显著提高,具有良好的塑韧性;同时,使合金的磁感生应变值有一定下降。  相似文献   

8.
研究了添加5种稀土元素对Ti0.26Zr0.07V0.24Mn0.1Ni0.33合金的微观结构和电化学性能的影响。结果表明,Ti0.26Zr0.07V0.24Mn0.1Ni0.33和Ti0.26Zr0.07V0.24Mn0.1Ni0.33RE0.01(RE=La,Ce,Pr,Nd,Gd)合金均由体心立方结构的BCC主相和少量六方结构的C14型Laves相组成;在合金中加入稀土元素,会使合金中两相的晶胞体积同时增大。添加5种稀土元素都可以改善合金电极的活化性能,而对合金电极其他性能的影响则各有不同,其中添加铈和镨可以提高合金电极的最大放电容量,而添加钕和钆能改善合金电极的循环稳定性。工作温度对合金电极的放电容量影响较大,过高的温度使其循环容量衰减加剧;而含稀土元素的合金电极在333K温度下放电容量达到最大值。稀土对合金电极的荷电保持率产生一定影响;镧、铈、镨的添加能够改善合金电极的倍率放电性能。  相似文献   

9.
混合稀土对Cu—Ni—Si铸态合金组织和电性能的影响   总被引:3,自引:0,他引:3  
研究了混合稀土对Cu-Ni-Si三元合金铸态组织和电性能的影响,观察到稀土元素的加入造成合金晶界共晶相的改变以及基体中相中针状η-NiSi的分析,同时稀土元素的加入对合金的电阻率和电阻温度系数产生明显的影响,使得合金的电阻温度系数随稀土加入量的增加呈从递减到递升的变化。  相似文献   

10.
采用透射电镜、膨胀仪和显微硬度测定等方法对含稀土和不含稀土的Si-Mn-V低碳钢马氏体自回火和低温回火分解过程进行了研究。结果表明,Si-Mn-V钢低碳马氏体自回火析出的碳化物既有ε-碳化物,又有θ-Fe_3C相,二者可以同时并存。而钢中含有少量稀土元素可以抑制低碳马氏体自回火碳化物的析出,影响自回火碳化物的析出类型。透射电镜原位动态观察还表明,稀土元素抑制了低碳马氏体在低温回火阶段的分解。  相似文献   

11.
考察了RE,Al对含钨高铬铸铁组织、冲击韧度、硬度、耐磨性等性能的影响。结果表明:铸态未变质的铸铁组织中,奥氏体含量多,碳化物呈粗大板条状分布,晶粒比较粗大;变质后残余奥氏体量明显减少,初生奥氏体显著细化,碳化物由粗大板条状向细板条状、菊花状转变;RE,Al复合变质处理可使铬钨合金白口铸铁的硬度、冲击韧度、耐磨性都得到提高。  相似文献   

12.
Valence-to-core X-ray emission spectroscopy was applied to study a composition of chromium coatings electrodeposited from Cr(III) sulfate electrolytes with the addition of formic or oxalic acid. It was shown that the obtained crystallographically amorphous deposits contain chromium carbide compounds. These results indicate that nanodimensional Cr crystallites formed during the electrodeposition process are characterized by very high electrocatalytic activity.  相似文献   

13.
The binder phase Co in WC-Co cemented carbide is dissolved easily in corrosive media (even in neutral solution), which has limited its application in a wider range. In this paper, the influence of Cr on corrosion resistance of WC-Co immersed in neutral solution was studied, with a focus on the surface chemistry of the corrosion product. The results show that in neutral solution, the corrosion is mainly caused by the selective dissolution of Co and the dominant surface corrosion product after immersion is Co (OH)2. The corrosion resistance of WC-Co cemented carbide can be improved by the addition of Cr. This can be explained by the formation of more protective chromium containing oxide on the binder phase of WC-Co-Cr alloy, leading to reduced corrosion rate.  相似文献   

14.
Summary An analysis of external parameters during the acquisition of the chromium measuring signal in biological material by ETA-AAS is presented. Some recommendations are given how to increase the reliability of the chromium values in biological material: By carbide formation in untreated graphite tubes the measuring signal is progressively decreased. Therefore, pyrolytically coated graphite tubes should be used. The reduction of the inert gas stream during electrothermical treatment of the biological sample might cause a too high, unspecific signal. This could also lead to false, increased chromium values.

Stipendiat der Carl Duisberg Gesellschaft e.V., Shandong Institut für Umweltschutz, Jinan, V. R. China  相似文献   

15.
李金波  朱杰武  郑茂盛 《电化学》2007,13(3):274-278
应用电化学阻抗谱技术研究铬对碳钢钝化膜半导体性能的影响.实验表明,在碳酸氢钠/碳酸钠缓冲溶液中碳钢形成的钝化膜具n型半导体特性,而含有3%铬的碳钢钝化膜则呈n-p型半导体特性,随着成膜电位的增加,以上两种钝化膜之Mott-Schottky直线部分的斜率均呈增大的趋势,表明成膜电位升高,膜内的杂质密度减小,但铬的加入使得碳钢钝化膜的施主密度增加约一个数量级,从而增加了碳钢点蚀发生的趋势.EIS分析表明:铬的加入降低了钝化膜的传递电阻R1和膜电阻R2,特别是膜电阻R2下降达3个数量级,这就有可能增加碳钢在高pH值环境中的腐蚀.  相似文献   

16.
The possibility was studied for synthesizing chromium oxide structures on the surface of K3–6 granular silicon carbide [GOST(State Standard 26327-84)] by its multiple successive treatment with chromium(VI) oxochloride, ethyl alcohol, and water vapors. The change in the chromium concentration in the modified samples was studied as a function of the number of successive treatment cycles. The samples were characterized by the X-ray phase analysis, X-ray photoelectron, IR, and electronic diffuse reflectance spectroscopies before and after the modification.  相似文献   

17.
Formation rates of hydrogen peroxide and electrode erosion rates for a range of different electrode materials were determined in a gas–liquid pulsed electrical discharge reactor with a high voltage electrode needle in the liquid and a ground electrode suspended in the gas over the liquid. It was found that the H2O2 formation rates and efficiencies did not depend on the electrode material. Electrode erosion from lowest to highest followed the series: nickel chromium, thoriated tungsten, diamond-coated tungsten, stainless steel, tungsten carbide and tungsten copper alloy. Smooth crater-like morphology was found for nickel chromium, titanium and tungsten carbide and a much finer surface structure with small protrusions for the tungsten, tungsten copper and the copper. Doubling the electrode diameter lead to an increase in the H2O2 formation per eroded length by a factor of three but it also decreased the energy efficiency yield of H2O2 by more than 20%.  相似文献   

18.
Surface layers formed at a contact of chromium with sulfuric acid solutions containing some organic substances (sodium oxalate, dimethylformamide, methanol) are analyzed by the X-ray photoelectron spectroscopy method. The layers are shown to contain products of deep destruction of organic molecules, i.e. carbon species and those containing functional groups. The data obtained point to the electrocatalytic activity of chromium in cathodic processes. The results of this study may provide a deeper insight into the mechanism of carbon incorporation (in the form of carbide compounds as well) into amorphous chromium deposits formed in sulfuric acid baths containing some organic substances.  相似文献   

19.
Summary Graphite atomization mechanisms of chromium in a graphite furnace are briefly reviewed and the influence of some compounds on stabilization of the analyte is investigated. For this purpose, charring curves for various salts and solvents were obtained. Elements which from stable oxides stabilize chromium oxide, avoiding losses of the volatile suboxide. Elements which form carbides and the organic solvents depress the signal due to the formation of chromium carbide.
Einige Beobachtungen zu den Stabilisierungsmechanismen von Chrom in der Graphitrohr-AAS
  相似文献   

20.
The determination of beryllium, barium and vanadium by atomic absorption spectrometry in an uncoated graphite furnace poses several problems, e.g. bad reproducibility, memory effects, etc. These difficulties can be avoided by using tubes coated with pyrolytic graphite and carbide. The optimal temperature for the pyrolytic graphite coating and the quantity of lanthanum that should be introduced for the carbide coating are discussed. Beryllium, barium and vanadium in surface water and tap water can be determined without memory effects and with detection limits of 0.01, 1 and 1μg l-1, respectively. Good agreement was found with the results obtained by activation analysis and flame or flameless (with uncoated tubes) atomic absorption spectrometry after preconcentration. The lifetime of the coated tubes was increased, and improved results were also found for the determination of other carbide-forming and/or high-melting elements such as molybdenum, cobalt, nickel, copper and chromium.  相似文献   

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