F.H.Cao
,
J.Q.Zhang
金属学报(英文版)
Spontaneous electrochemical noise(EN)can be a rich source of information concern-ing the processes simultaneously occurring at a corroding interface.Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride solution are investigated,and the breakdowm and restoration of passive metal's film are studied using potentiodynamic scanning(PDS)measure-ments and electrochemical impedance spectroscopy(EIS)technique.Two capacitance loops are observed in the Nyquist plots in two kinds of concentration,and the corro-sion process is under activation control at first,then become diffusion control within the oxide film and corrosion products of (Al(OH)p-mClm^-)accumulated on the surface of the corroding electrode.It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wtthan in 2.0wtaCl solution,and the high concentration of chloride ion in solution inhibits the repassivation of a metastable pit.The corrosion rate deterministic step does not involve Cl^-.
关键词:
pure aluminum
,
null
,
null
Y.L.Cheng
,
J.F.Li
,
J.Q.Zhang
,
C.N.Cao
,
F.H.Cao
,
Z.Zhanq
金属学报(英文版)
The electrochemical features of commercial airframe material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (Na2SO4) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiody-namic polarization techniques. The microstructure of the as-tested samples was stud-ied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different features, indicating that the Cl^- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO4^2- solution isn't easy to dis-solve, and it urill cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.
关键词:
LY12 aluminum alloy
,
null
,
null
李亚宁
,
董保胜
,
赵新伟
,
罗金恒
,
周根树
,
郑茂盛
钢铁研究
doi:10.3969/j.issn.1001-1447.2006.03.010
Q345是广泛使用的一种普通低合金钢,其断裂韧性是工程中进行裂纹检测的重要参数.应用J积分法测定了Q345的断裂韧性,并采用R6方法中的选择3曲线和通用曲线绘制了其失效评定曲线.研究发现:所有试样断口均有充分张开的大分层现象,它的存在阻碍了断口沿厚度方向的收缩,从而增加了材料的断裂韧性值.给出了适合Q345特性的失效评定曲线,以便为工程应用提供依据.
关键词:
Q345
,
J积分
,
断裂韧性
,
失效评估曲线
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
Physical Review B
The Hamiltonian for a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab) = J(cd) not equal J(bc) = J(da)) was established. An extended Bogoliubov transformation was developed by solving an equation group, consisting of 20 equations and 20 unknowns. The procedure for solving the equation group was carried out by introducing a simple way of reducing the numbers of the equations and the unknowns. The spin-wave spectra in the present system have been determined by performing the standard Holstein-Primakoff transformation and the Bogoliubov one. It has been found that the spin-wave spectra of the present system depend on the exchange constants and that the degeneracy of the spin-wave spectra remains. The results for a special case (J(ab) = J(bc)) i.e., an antiferromagnet are discussed briefly. The spin-wave spectra of the four-sublattice Heisenberg antiferromagnet are found to be degenerative also and they are linear in k for small k.
关键词:
model
Y.G. Cao
,
X.Y. Sun
金属学报(英文版)
J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.
关键词:
FRASTA
,
null
,
null
鲁二敬
,
卢峰华
,
许鸿吉
,
谢明
,
钮旭晶
机械工程材料
通过周期浸润腐蚀试验，对比研究了S355．12W耐候钢和Q345R低合金钢在NariSOs溶液中的耐腐蚀性能，并用扫描电镜对腐蚀产物进行了观察和分析。结果表明：在相同试验条件下，S355J2W耐候钢的腐蚀速率低于Q345R钢的；S355J2W耐候钢会在表面形成黑褐色锈层，而Q345R钢表面形成橘红色易剥落的疏松锈层；S355J2W耐候钢腐蚀产物微观形貌为沿放射性方向生长的针状晶体，Q345R钢为颗粒状聚合物堆积而成，形状无规则，颗粒之间有较大的空隙。
关键词:
S355J2W耐候钢
,
周期浸润腐蚀试验
,
耐腐蚀性能
