Manpreet Singh Marwah
,
Vajjala Srinivas
,
Ajoy Kumar Pandey
,
Shyam Ranjan Kumar4
,
Koushik Biswas
,
Joydeep Maity5
钢铁研究学报(英文版)
Steel containing carbon of 02% was coated with Ni and Cr through electrodeposition, and subsequently annealed at 400 and 600 ℃ for 5 min, 30 min, 1 h and 2 h. During annealing at 400 ℃, the formation and growth of oxides occurred in the form of petals along with voids, cracks and porosities. However, at 600 ℃, the nucleation and growth of chromium oxide whiskers produced a surface almost free from crack, porosity and void for 1 h and 2 h of holding. In accordance with the surface morphology, the bare steel, as-deposited steel, all specimens deposited and annealed at 400 ℃, and specimens deposited and annealed at 600 ℃ for 5 and 30 min exhibited continuous corrosion in 3% of NaCl solution. However, the specimens deposited and annealed at 600 ℃ for 1 and 2 h exhibited an improved corrosion resistance in 3% of NaCl solution with high pitting potential due to presence of a dense passive oxide film almost free from voids at the surface.
关键词:
steel
,
electrodeposition
,
annealing
,
corrosion resistance
Journal of Applied Physics
The temperature dependence of the magnetic anisotropy constant K1 for SmCo5 and GdCo5 is well reproduced by calculations based on a single-ion model taking into account the anisotropies of the R-Co exchange interaction and the Co-sublattice magnetic moment. The anisotropy of the R-Co exchange interaction plays an important role in reproducing the experimental K1(T) for SmCo5 and GdCo5. It is found that the absolute value of the second order crystalline electric field parameter A2(0) in SmCo5 decreases monotonically with increasing temperature.
关键词:
intermetallics
张康侯
稀有金属材料与工程
稀土金属对富Pd合金的氢化性能、磁学性能和催化性能有显著的影响,对Pd-RE合金系中最富Pd的化合物的研究是有意义的.本工作通过恰当的熔炼和热处理工艺制备出单相的金属间化合物CePd5,PrPd5和NdPd5,并应用X射线衍射分析确定了它们的晶体结构和晶格参数.研究发现:在Pd-Ce二元系中,最富Pd的化合物是具有CaCu5型六方结构的CePd5;而在Pd-Pr和Pd-Nd二元系中最富Pd的化合物分别是具有SmPt5型正交结构的PrPd5和NdPd5.报道了经指标化的这3种金属间化合物的x射线衍射数据,确定CePd5的晶格参数a=0.5372 nm,c=0.4178 nm;PrPd5和NdPd5的晶格参数分别是a=0.5278 nm,b=0.9239 nm,c=2.575 am和a=0.5265 nm,b=0.9219 nm,c=2.570 nm.并对Pd-RE合金系和Pt-RE合金系中最富Pd化合物的化学计量和晶体结构进行了对比.
关键词:
金属间化合物CePd5
,
PrPd5
,
NdPd5
,
X射线衍射数据
,
晶体结构
杨应昌
,
何文望
,
林勤
金属学报
本文研究了RECo_5在居里温度附近热膨胀反常的特点。利用高温X射线衍射方法从室温到600℃测定了CeCo_5,Ce(Co_(0.6)Cu_(0.2))_5和Ce(Co_(0.9)Fe_(0.1))_5晶格常数α和c随温度的变化。在居里点附近,CeCo_5的晶格常数c随温度的变化存在明显的拐折,在磁有序区域内具有因瓦反常,而晶格常数α随温度基本保持连续线性的变化,没有反常效应.用Cu原子部分取代Co原子以后,Ce(Co_(0.3)Cu_(0.2))_5沿c轴的热膨胀反常显著减弱。利用中子衍射研究了RE(Co,Cu)_5结构的有序性,从中子衍射的谱线分析表明,在CaCu_5型结构的RE(Co,Cu)_5金属间化合物中,Cu原子优先占据2c位置,由此解释了RECo_5热膨胀反常的原因。
关键词:
Journal of Alloys and Compounds
Phase relationships at ambient temperature in the pseudobinary system Nd5Si4-Nd5Ge4 were studied by X-ray powder diffraction (XRD). Four structurally distinct phase regions exist in this system. The Nd5Si4-based solid solution in which Ge statistically substitutes for Si crystallizes in the tetragonal Zr5Si4-type structure with space group P4(1)2(1)2. The Nd5Ge4-based solid solution in which Si statistically substitutes for Ge crystallizes in the orthorhombic Gd5Ge4-type structure with space group Pnma. There are two ternary intermediate phases, which crystallize in the orthorhombic Gd5Si4-type structure with space group Pnma and the monoclinic Gd5Si2Ge2-type structure with space group P112(1)/a. The Rietveld powder diffraction profile fitting technique was used for refinement of the crystal structure. The lattice parameters, atomic positions and interatomic distances for Nd5Si4, Nd5Si2.8Ge1.2, Nd5Si2Ge2 and Nd5Ge4 were derived. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
rare earth compounds;crystal structure;X-ray diffraction;gd-5(si2ge2);transition;gd-5(sixge1-x)(4)
李明
,
宋月清
,
崔舜
,
于兴哲
,
李增德
稀有金属
doi:10.3969/j.issn.0258-7076.2007.04.004
采用真空自耗重熔法制备了V5Cr5Ti合金,测试了V5Cr5Ti合金的高温拉伸性能,分析了高温拉伸断口的宏观、微观形貌,探讨了钒合金的断裂机理.结果表明:随温度升高,V5Cr5Ti合金的强度性能下降,塑性性能先降低后升高;在700～900 ℃,V5Cr5Ti合金仍具有良好的强韧性综合性能;其高温断口特征表现为韧性断裂为主,韧性和脆性特征共存的现象.
关键词:
真空自耗重熔
,
V5Cr5Ti
,
高温拉伸性能
,
韧性断裂
,
脆性断裂
李增德
,
崔舜
,
林晨光
,
李明
稀有金属
doi:10.3969/j.issn.0258-7076.2009.06.004
研究了V-5Cr-5Ti合金在900～1100 ℃之间的再结晶规律, 概括了V-5Cr-5Ti合金的再结晶动力学机制. 结果表明, 合金冷变形板材在950～1050 ℃下退火处理, 可获得细小、均匀的等轴晶; 初步推导了V-5Cr-5Ti合金再结晶动力学机制, 符合Avrami-Erofeev形核长大机制; 并计算了V-5Cr-5Ti合金再结晶激活能Q_r, 其值为261.91～289.67 kJ· mol~(-1).
关键词:
V-5Cr-5Ti合金
,
再结晶
,
动力学机制
,
激活能
吕曼祺
,
银耀德
,
吴桂春
,
吴平森
金属学报
本文通过对LaNi_5活化过程动力学的研究,论证了LaNi_5的清洁表面具有使氢分子分解为氢原子的催化作用。这种催化作用因氧在表面的存在而丧失,活化过程就是清除氧的污染而形成清洁表面的过程。孕育期的存在是表面污染引起的,已活化的LaNi_5中未释放的氢可减轻氧对LaNi_5表面活性的影响。
关键词:
Journal of Alloys and Compounds
Phase relationships at ambient temperature in the pseudobinary system Pr5Si4-Pr5Ge4 were studied by X-ray powder diffraction (XRD). Three structurally distinct phase regions exist in this system. The Pr5Si4-based solid solution where Ge statistically substitutes for Si crystallizes in the Zr5Si4-type tetragonal structure with space group P4(1)2(1)2. The Pr5Ge4-based solid solution where Si statistically substitutes for Ge crystallizes in Sm5Ge4-type orthorhombic structure with space group Pnma. The crystal structure of a ternary intermediate phase, which exists between 1.65 less than or equal to x less than or equal to 2.6, is determined for the first time, and shown to be the Gd5Si2Ge2-type monoclinic structure with space group P112(1)/a. The Rietveld powder diffraction profile fitting technique was used for the refinement of crystal structure. The lattice parameters, atomic occupations, interatomic distances of the Pr5Si4, Pr5Ge4 and Pr5Si2Ge2 compounds were derived. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
rare earth compounds;crystal structure;X-ray diffraction;gd-5(si2ge2);transition;gd-5(sixge1-x)(4)
