Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl solution at 100 °C with cyclic potentiodynamic polarization and constant-potential tests. The corrosion damage morphologies, corrosion products, and the compositions of corroded surfaces of these two alloys were studied with optical three-dimensional reconstruction, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Auger electron spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant-potential tests. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained a high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys corroded congruently in the crevice corrosion damage areas. This article is based on a presentation given in the symposium entitled “Iron-Based Amorphous Metals: An Important Family of High-Performance Corrosion-Resistant Materials,” which occurred during the MSandT meeting, September 16–20, 2007, in Detroit, Michigan, under the auspices of The American Ceramics Society (ACerS), The Association for Iron and Steel Technology (AIST), ASM International, and TMS.

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The Effect of Temperature on the Preferential Intergranular Oxidation Susceptibility of Alloy 600

Metallurgical and Materials Transactions A - Oxidation studies were performed on solution-annealed Alloy 600 in high-temperature steam at 400 °C and in simulated pressurized water...     

热处理对Cu50Zr42Al8块状非晶力学性能的影响

采用铜模吸铸法成功制备了Cu50Zr42Al8块状非晶,用纳米压痕法研究了铸态和低于玻璃化转变温度(Tg)退火后试样的力学性能,等温退火后试样的塑性增加而硬度和弹性减小。     

Dy含量对Mg—Dy—Nd合金组织与力学性能的影响

探讨了稀土元素Dy含量对Mg—Dy—Nd合金力学性能与组织的影响变化规律。力学性能测试结果表明随着Dy元素含量的增加，合金抗拉强度几乎成直线增加，屈服强度有不明显增加，塑性变型降低明显。采用扫描电子显微镜及晶相显微镜分析了不同Dy含量下，Mg-Dy—Nd合金的微观形貌及组织形态，初步分析了该合金的断裂机理。     

FeCuNbSiB-La非晶软磁合金的静态磁性能

对于不同稀土加入量的非晶软磁合金的静态磁性能与热处理制度和稀土加入量的关系做了比较。结果表明，稀土加入量较高的合金其相应最佳性能（矫顽力较低）的热处理温度稍高，温度区间要窄。稀土加入量为１ａｔ％的非晶软磁合金的初始磁导率可达１．７×１０４。     

铜对碳钢耐大气腐蚀性能的影响

通过实验室干湿周浸加速腐蚀试验，研究了模拟工业大气环境下，合金元素Cu对碳钢耐腐蚀性能的影响。利用XRD测定腐蚀产物的相组成，通过SEM观察腐蚀试样表面及截面形貌。结合失重法及电化学方法对Cu提高碳钢耐腐蚀性能的机理进行研究分析。结果表明：Cu对碳钢耐腐蚀性能具有明显的促进作用，添加025％的Cu使碳钢的腐蚀速率明显下降，腐蚀抗力平均提高65％以上，含铜钢的腐蚀产物主要由稳定的aαFeOOH及少量γ-FeOOH构成，锈层较碳钢锈层更加致密，腐蚀电流较小。     

用阻抗方法分析添加剂对Ni—P非晶态电沉积的影响

应用交流阻抗方法,研究添加剂对非晶态电沉积的影响是一种较新的手段。本文采用阻抗的方法初步研究了不同类型添加剂在Ni—P非晶电沉积中的作用机理。结果表明,洗涤剂作为Ni—P电镀添加剂可以改善其镀层质量,有利于非晶镀层的形成。该研究方法有效可行值得重视。     

模拟焊接条件对镍磷非晶态合金结构和性能的影响

通过不同的热处理条件模拟焊接过程的温度和时间,对化学镀N1-P非晶态合金的结构、性能进行了研究。结果表明:当热处理时间在60s以内时,Ni-P合金不会发生晶化(1000℃,60s除外),仍然保持非晶态,但是镀层硬度明显得到了提高,在较短时间的热处理条件下,镀层硬度在700℃处取得最大值。     

Stress-State Effects on the Fracture of a Zr-Ti-Ni-Cu-Be Bulk Amorphous Alloy

The effects of wide changes in stress state on the flow and fracture behavior of a single Zr-Ti-Ni-Cu-Be bulk metallic glass (BMG) of known chemistry are summarized. Both compression and tension samples were tested with superimposed hydrostatic pressures up to 1230 MPa in addition to notched tension samples tested at 0.1 MPa as well as with 490 MPa superimposed pressure. A wider range of stress states were obtained by including compression experiments conducted in pressure/shear conditions with normal stresses up to 8.7 GPa. The critical shear stress at fracture in the present BMG chemistry and sample dimensions tested is relatively unaffected by these significant changes in stress state, again indicating the normal stress/pressure dependence of flow in this particular BMG chemistry and processing conditions is vanishingly small. The present results are compared to those obtained on other metallic glasses tested under similar conditions and those that exhibit inclusion-initiated failure that demonstrate a much different dependence for similar changes in stress state.     

Effect of Heat Treatment on the Microstructure and Corrosion Resistance of Cu-Zn Alloy

The microstructure of Cu-Zn alloy with different heat treatment conditions in 3.5% NaCl NH3 solution were observed, and the average corrosion rates and electrochemical data of Cu-Zn alloy were measured, as well as the effect of heat treatment on microstructure and corrosion resistance of Cu-Zn alloy was analyzed. The results show that the microstructure of Cu-Zn alloy has been changed due to the heat treatment. As a results, the better corrosion resistance can be obtained for the Cu-Zn alloy quenched from 900℃ for 0.5h followed by tempered at 100℃ for 2h.     

Nd-Fe-B合金的组织与组成对其腐蚀行为的影响

研究了Nd-Fe-B合金的组织与组成对其腐蚀行为的影响。对Nd-Fe-B合金各主要组成相在纯水和NaCl溶液中电位进行了测定,结果表明E_(富Nd相)(基体相)(富B相)。Nd-Fe-B合金的腐蚀特征是晶界处的富钕相优先腐蚀,然后向晶粒内Nd₂Fe₁₄B基体相扩展。环境腐蚀试验结果表明,Nd-Fe-B合金中加入Dy后,耐蚀性提高;加入Al后,则耐蚀性有所下降。     

Fe—P非晶合金电沉积镀层的制备及其腐蚀性能

本文以电化学方法研制Fe—P非晶合金的电沉积镀层。研究了各种电沉积条件对合金中磷含量的影响。测定了非晶合金的腐蚀性和极化曲线。实验结果指出,在开始阶段合金是活化腐蚀,合金中的磷加快了腐蚀过程,最后磷在表面的富集,使合金进入钝化状态。 对非晶合金电沉积镀层的晶化温度和硬度进行了测定。     

镍含量对(Zr_(0.83)Cu_(0.17))_(88-x)Al_(12)Ni_x非晶形成能力和力学性能的影响

利用铜模吸铸法制备(Zr0.83Cu0.17)88-x Al12Nix非晶合金,考察了镍含量对合金非晶形成能力和力学性能的影响。结果表明,在镍含量比较低时,合金并不是完全的非晶合金,有部分晶体析出;而当镍的质量分数为10%时,所得到的非晶合金断裂强度和塑性应变分别达到1 679 MPa和7.56%,此时过冷液相区的宽度ΔT=84.64K,该组分的合金具有较强的非晶形成能力。     

Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

A stable Ni-rich Ni-29.7Ti-20Hf (at. pct) shape memory alloy, with relatively high transformation temperatures, was shown to exhibit promising properties at lower raw material cost when compared to typical NiTi-X (X = Pt, Pd, Au) high-temperature shape memory alloys (HTSMAs). The excellent dimensional stability and high work output for this alloy were attributed to a coherent, nanometer size precipitate phase observed using transmission electron microscopy. To establish an understanding of the role of these precipitates on the microstructure and ensuing stability of the NiTiHf alloy, a detailed study of the micromechanical and microstructural behaviors was performed. In-situ neutron diffraction at stress and temperature was used to obtain quantitative information on phase-specific internal strain, texture, and phase volume fractions during both isothermal and isobaric testing of the alloy. During isothermal testing, the alloy exhibited low isothermal strains due to limited detwinning, consistent with direct measurements of the bulk texture through neutron diffraction. This limited detwinning was attributed to the pinning of twin and variant boundaries by the dispersion of fine precipitates. During isobaric thermal cycling at 400?MPa, the high work output and near-perfect dimensional stability was attributed to the presence of the precipitates that act as homogeneous sources for the nucleation of martensite throughout the material, while providing resistance to irrecoverable processes such as plastic deformation.     

Corrosion Fatigue Study of 6061 Aluminum Alloy: The Effect of Coatings on the Fatigue Characteristics

Metallurgical and Materials Transactions A - This study proposes a method for protecting 6061 aluminum alloy from corrosion fatigue. Corrosion fatigue can reduce fatigue strength at the endurance...     

Effect of Thermal Aging on the Corrosion and Microstructure of Friction-Stir Welded Alloy 22

The effect of thermal aging on the corrosion and microstructure of friction-stir welded (FSW) alloy 22 was investigated. Successful welds were produced with a polycrystalline cubic BN pin tool at a rotational speed of 200 rev min^?1 and travel speed of 12.7 mm min^?1. Topologically closed packed (TCP) phases of ~50 to 300 nm size were identified in the weld nugget. The area fraction of the TCP phases in the weld nugget increased with aging temperature and time. General corrosion rates measured from the weight loss experiments for welds were relatively higher than for parent material. The corrosion rates increased with the increased aging temperature and time. Intergranular corrosion (IGC) resistance is greater in friction-stir welds compared with the parent material at all aging temperatures and times. The IGC depth increased with the aging temperature and time in the parent material. The IGC depth for the FSW weld nugget was minimal and did not change with thermal aging.     

Effect of Refractory Boride Particles on Crystallization of the Amorphous Alloy Fe85B15

We have studied the characteristic features of the process of transition from the amorphous to the crystalline state in the presence of refractory boride particles of different crystallographic types (zirconium diboride ZrB₂ and lanthanum hexaboride LaB₆), introduced into ribbons of Fe₈₅B₁₅ amorphous alloy directly during ribbon formation. ZrB₂ particles in the base alloy have practically no effect on its thermal stability, defined by the temperature of onset of formation of primary α-Fe crystals, while in the presence of LaB₆ particles the thermal stability is considerably reduced. This qualitatively correlates with the Dankov principle of structural and dimensional correspondence considered in the theory of heterogeneous nucleation. We have shown that the major factor determining the high catalytic activity of LaB₆ particles with respect to nucleation of α-Fe crystallization centers is rapid chemical reaction within the zone where they come in contact with the Fe₈₅B₁₅ melt. The ZrB₂ particles which do not enter into such a reaction, do not affect the course of crystallization processes and the thermal stability of the base amorphous alloy.     

激光功率对SLM制备非晶合金成形及晶化的影响

非晶合金以其独特的原子排列和优异的性能引起人们的广泛关注,但由于尺寸、晶化等问题严重限制了实际工程中的应用,激光增材制造技术具有高升温-冷却速率和逐点熔融沉积的特点,为制备非晶合金提供了新思路.本文采用选择性激光熔融成型技术制备Zr50Ti5Cu27Ni10Al8非晶合金.对制备出的样品的成分和组织结构进行了表征.结果...     

碳含量和组织类型对低合金钢耐蚀性的影响

 研究了碳含量不同和显微组织不同的低合金钢的耐腐蚀性能和腐蚀行为,并和商业耐候钢09CuPCrNi做了相应的比较。在碳含量比较低的情况下,组织类型对试验钢的耐蚀性影响不大;碳含量比较高时,单相贝氏体钢的耐蚀性优于由铁素体、渗碳体(珠光体)等构成的复相组织钢。轧后水冷时,不同碳含量的钢耐蚀性差别不大;轧后空冷时,碳含量低的钢的耐蚀性优于碳含量较高的钢。用扫描电镜对锈层进行观察,可以看出耐蚀性较好的试样在腐蚀后期形成了较致密的内锈层。碳的质量分数分别为0.03%和0.1%的钢水冷后的平均腐蚀速率相差很小,但从微观角度看其点蚀发展趋势不同。加速腐蚀5个周期后,w(C)为003%的水冷钢中蚀坑尺寸不再增加,而w(C)为01%的钢中蚀坑尺寸仍有增加趋势。     

The Effects of Low Cu Additions and Predeformation on the Precipitation in a 6060 Al-Mg-Si Alloy

Effects of low Cu additions (≤0.10 wt pct) and 10 pct predeformation before aging on precipitates’ microstructures and types in a 6060 Al-Mg-Si alloy have been investigated using transmission electron microscopy (TEM). It was found that predeformation enhances precipitation kinetics and leads to formation of heterogeneous precipitate distributions along dislocation lines. These precipitates were often disordered. Cu additions caused finer microstructures, which resulted in the highest hardness of materials, in both the undeformed and the predeformed conditions. The introduced predeformation led to microstructure coarsening. This effect was less pronounced in the presence of Cu. The precipitate structure was studied in detail by high-resolution TEM and high angle annular dark-field scanning TEM (HAADF-STEM). The Cu additions did not alter the respective precipitation sequence in either the undeformed or the predeformed conditions, but caused a large fraction of β″ precipitates to be partially disordered in the undeformed conditions. Cu atomic columns were found in all the investigated precipitates, except for perfect β″. Although no unit cell was observed in the disordered precipitates, the presence of a periodicity having hexagonal symmetry along the precipitate length was inferred from the fast Fourier transforms (FFT) of HRTEM images, and sometimes directly observed in filtered HAADF-STEM images.