铝锡轴承合金的摩擦磨损机理与性能

铝锡轴承合金对大型载重汽车、坦克、高速汽车、拖拉机等的高速高压柴油机的发展有重要的意义。提高铝锡合金的耐摩擦磨损性能可节省大量能源并延长零件的使用寿命,如何取得具有优良的耐摩擦磨损的铝锡合金成为研究的重点。本文介绍了提高铝锡合金的耐摩擦磨损性能的措施及其影响因素,总结铝锡合金中锡元素含量改变、合金元素的添加、热处理与制备工艺的改变对铝锡合金的显微组织以及耐摩擦磨损性能的影响。     

Studies on induction hardening of powder-metallurgy-processed Fe-Cr/Mo alloys

Induction hardening of dense Fe-Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2-3 s. A case depth of 2.5 mm was achieved while maintaining the bulk (interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C.     

Effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of B–Y modified silicide coating

B–Y modified silicide coatings were prepared on Nb–Si based alloy by pack cementation at 1300 ℃ for 10 h. The effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of the coatings was investigated. The results show that the four coatings have similar structures, which possess a(Nb,X)Si_2 outer layer and a(Nb,X)_5Si_3 transitional layer. Y_2O_3 content in the pack mixtures has an obvious effect on the Si content in the coating. The mass gains of the coatings prepared with 0.5, 1, 2 and 3 wt% Y_2O_3 in pack mixtures are 2.33, 1.96, 2.05 and 2.86 mg/cm~2 after oxidation at 1250 ℃ for 100 h, respectively. The coating prepared with 1 wt% Y_2O_3 exhibits the best oxidation resistance due to the formation of a dense glass-like borosilicate scale.     

Atomic-scale segregation behavior of Sn/Ti and O at Σ3[11¯0](111) grain boundary in niobium

First-principle calculation was performed to illustrate the atomic arrangement and segregation behavior of Sn/Ti and O in View the MathML source grain boundary, and the interaction of oxygen interstitials with Sn/Ti atoms on the grain boundary was studied. The analyses on the segregation energies and geometric positions, and the electron densities show that Sn, Ti and O atoms segregate at the Σ3 grain boundary. And the preferred segregation sites of the impurities at View the MathML source were determined. When Sn segregates at grain boundary plane, the O atom prefers to the bulk-like site and shows no segregation tendency at grain boundary, whereas the segregated Ti atom can slightly enhance oxygen segregation at the grain boundary.     

热处理对镍基合金涂层与基体结合界面的影响

通过热浸镀法在普碳钢表面成功制备镍基合金涂层.为了提高镍基合金涂层与钢基体之间的结合强度,对镀有镍基合金涂层的基体进行了热处理.研究了热处理前、后结合界面处的显微组织和力学性能.结果表明,与热处理前相比,热处理后界面附近的涂层中析出物长大,界面处存在不连续块状铁的硼化物,界面两侧镍、铁互扩散距离增加,靠近界面的过渡带由5～8μm变为20μm.热处理前、后涂层均由γ-(Fe,Ni)、CrB、Cr2B和Cr3C2等相组成,过渡带相组成为γ-(Fe,Ni)、微量CrB和Fe23(C,B)6.热处理后,显微硬度由界面向涂层内逐渐增加,界面结合强度由140MPa提高到200MPa.     

连续柱状晶组织BFe10-1-1合金的电化学腐蚀性能

采用线性极化、电化学阻抗谱等电化学方法研究了连续柱状晶组织BFe10-1-1合金在3.5%（质量分数）NaCl溶液中的耐蚀性能,并与普通铸造多晶组织BFe10-1-1合金进行了对比.极化曲线测试结果表明,两种合金具有相似的电化学行为,极化曲线都包括活性溶解区、活化-钝化转变区和极限电流区,但连续柱状晶组织合金腐蚀速率小于普通铸造多晶组织合金,主要是由于连续柱状晶组织BFe10-1-1合金的微观偏析程度较小,能有效避免枝晶间局部腐蚀的发生.电化学阻抗谱测试结果也表明,该合金的电荷传递电阻和腐蚀产物膜电阻均大于普通铸造多晶组织合金,具有更高的耐蚀性.     

X射线光电子能谱检测热喷涂锌铝合金防腐性能的研究

锌铝合金可用作为风力发电装置的防腐材料.采用X射线光电子能谱（XPS）研究了由热喷涂方法制备的不同含量铝锌合金制得的TJPTZA1^#、TJPTZA2^#、TJPTZA3^#和TJPTZA4^#合金的防腐蚀性能,探究了合金与基体界面处的物质成分.使用能谱检测手段探索了界面处的元素成分及其含量,从而为以上合金的防腐性能研究提供依据.     

Rapid reductive degradation of azo dyes by a unique structure of amorphous alloys

An Fe-based amorphous alloy was found to significantly enhance the reductive degradation of an azo dye in aqueous solution. The surface-area normalized rate constant was up to 2.0 L m-2 min-1 at room temperature,an order of magnitude larger than any previously reported value. The activation energy of the degradation process was calculated according to the Arrhenius equation,and a much lower value than those previously reported was obtained. Valence band measurement indicated that a depressed valence band maximum and a widened empty band were established in the amorphous ribbon. The unique structure of the amorphous alloy is important-it may reduce the activation energy of the degradation process and enhance the activity of the electrons,thus accelerating the degradation process.     

Effect of Si on austenite stabilization,martensite morphology,and magnetic properties in Fe-26%Ni-x%Si alloys

The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si (x=3.5, 5, and 6) alloys have been studied by means of transmission electron microscopy (TEM) and M?ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mssbauer spectroscopy. The M?ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.     

Fe—Cr—Ni三元合金电镀初探

本文研究在氯化物电解液中制备类似18-8不锈钢成份的 Fe Cr-Ni 三元合金镀层。采用这种工艺规范所得到的铁铬镍三元合金外观呈银白色,镀层铁铬镍含量分别是:58.0%～66.4%,19.5%～22.5%,14.4%～19.2%,还含有少量 Ti 等微量元素.镀层结合力良好,耐腐蚀符合不锈钢要求。