J.S.Yu
,
C.G.Zhou
,
H.B.Xu
金属学报(英文版)
The oxidations of low pressure plasma sprayed (LPPS) NiCrAlY coating on nickelbase superalloy were studied at 1050C in flows of O2, and mixture of O2 and 5%H2 Ounder atmospheric pressure. Oxide formed on the surface of LPPS NiCrAlY coatingafter oxidation at 1050℃ in pure O2 consisted of NiCr2 O4, whereas oxide formed onthe surface of LPPS NiCrAlY coating after oxidation at 1000℃ in a mixture of O2 and5%H2 O is mainly composed of NiO. The effect of water vapor on the characteristicsof the oxide scale is attributed to the increase in Ni cation transport.
关键词:
oxidation
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null
,
null
Y.Q.Ma
,
C.B.Jiang
,
H.B.Xu
金属学报(英文版)
Cu-Al-Co and Cu-Al-Zr alloys were explored with Co or Zr additions in Cu-Al alloys for high temperature shape memory alloys. Samples were quenched after homogenized at 850℃ for 48h. It was found that both Cu-Al-Co and Cu-Al-Zr show AlCus martensitic phase at room temperature and exhibit martensitic transformation temperatureshigher than 200℃, showing the potentials for developing as high temperature shape memory alloys. Thermal cycles were performed by DSC instrument on both Cu-Al-Co and Cu-Al-Zr alloys. The results show that Cu-Al-Co loses its martensitic transformation after five thermal cycles, and Cu-Al-Zr exhibits no martensitic transformation in the second thermal cycle.
关键词:
shape memory alloy
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null
F.S.Liu
,
J.L.Xu
,
C.G.Zhou
,
S.K.Gong
,
H.B.Xu
金属学报(英文版)
The halide-activated pack cementation method is utilized to codeposit aluminum and silicon on Mo substrate. Emphasis is placed on the microstructure and elevated-temperature oxidation resistance of coatings. The results show that hexagonal Mo (Si, Al)2 as a main phase and a little amount of the lower disilicide Mo3Si3 was formed on Mo substrate through the halide-activated pack cementation method. The resultant Si-Al coating on Mo substrate exhibits excellent cyclic oxidation resistance. The excellent cyclic oxidation resistance of the coatings is attributed to the formation of alumina on the coatings during the oxidation.
关键词:
Mo(Si
,
null
,
null
,
null
X.F.Bi
,
S.K.Gong
,
H.B.Xu
金属学报(英文版)
Fe-Cu thin films of 0.2μm in thickness with different Cu contents were prepared byusing r.f. magnetron sputtering onto glass substrate. The effect of sputtering param-eters, including Ar gas pressure and input rf power, on the structure and magneticproperties was investigated. It was found that when the power is lower than 70W,the structure of the films remained single bcc-Fe phase with Cu solubility of up to50at.%. TEM observations for the bcc-Fe phase showed that the grain size was inthe nanometer range of less than 20nm. The coercivity of Fe-Cu films was largelyaffected by not only Ar gas pressure but also rf power, and reached about 2.5Oe in thepressure of 0.67-6.67Pa and in the power of less than 100W. In addition, saturationmagnetization, with Cu content less than 60at.%, was about proportional to the con-tent of bcc-Fe. When Cu content was at 60at.%, however, saturation magnetizationwas much smaller than its calculation value.
关键词:
Fe-Cu thin film
,
null
,
null
,
null
D.B.Zhang
,
S.K.Gong
,
H.B.Xu
金属学报(英文版)
Conventional two-layered structure thermal barrier coatings (TBCs) were preparedonto γ'-Ni3Al based alloy IC-6 by electron beam physical vapor deposition (EB-PVD).Isothermal oxidation and thermal cycling tests were carried out to investigate theeffect of Mo content at the interface between bond coat and ceramic top coat causedby diffusion. It has been found that the alloy coated with TBCs presented the lowestoxidation weight gain value for the reason that the ceramic top coat in TBC systemcan effectively stop Mo oxides evaporating. The life time of TBCs has close relationwith Mo content at the interface between the bond coat and top coat. Spallation ofceramic top coat occurred during thermal cyclic testing when Mo atoms accumulatedat the interface up to certain amount to decline the combination between the bond coatand top coat.
关键词:
EB-PVD
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null
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null
,
null
毕大森
,
武晋
,
张建
,
彭本栋
材料开发与应用
doi:10.3969/j.issn.1003-1545.2009.01.003
高强度烘烤强化(BH)钢是汽车覆盖件用的高强度钢板.本文通过试验对汽车用高强度钢板B180H1的力学性能、成形性能、烘烤硬化性能和抗凹陷性能进行了全面的研究,并与DC04钢板的各项性能进行了比较.使用NADDRG模型对B180H1钢的成形极限进行了预测.试验结果表明,B180H1的力学性能优于DC04,成形性能不低于DC04,且B180H1的烘烤硬化性能及抗凹陷性能方面均优于DC04.B180H1钢板的实冲壳体也具有良好的成形性能.
关键词:
汽车轻量化
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高强度钢板
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烘烤硬化
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成形性能
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抗凹陷性
Y.L. Chen(Department of Materials Science and Engineering
,
Zhejiang University
,
Hangzhou 310027
,
China)
金属学报(英文版)
Internal friction measurements on binary and ternary α-phase alloys of Pd with hydrogen and boron have been performed with a torsion pendulum and by observing the cttenuation of ultrasonic pulses. A pronounced damping maximum of binary Pd-B alloys at 220K and measuring frequencies of about 4Hz could not be established at a frequency of 15MH. Ternary Pd-B-H alloys show an additional damping maximum besides the hydrogen Zener effect, which is interpreted in terms of a changed jump frequency of hydrogen in the neighborhood of boron atoms.
关键词:
Pd-B-H alioy
,
null
,
null
,
null
Physical Review B
By using a first-principles plane-wave pseudopotential method, the energetics and electronic structure of Sigma5(210) grain boundary (GB) and the (210) surface of undoped as well as B- and/or H-doped Ni3Al are investigated. The geometric structures of the GBs and surfaces are fully relaxed by minimizing the total energy and interatomic force. The results show that B induces a large lattice expansion but H does not. Both B and H "prefer" to occupy the Ni-rich hole at the GB or surface but not the Ni-deficient one. The segregation energies of B and H as well as the interaction energy between them at the GB and surface are calculated. The calculation indicates that B segregates more strongly to the GB than to the surface, which results in an increase in the Griffith work of the GB and, therefore, in agreement with the experiments, improves the ductility of Ni3Al. Contrary to the case of B, H segregates more strongly to the surface than to the GB, which results in a decrease in Griffith work and confirms H as an embrittler for Ni3Al. The calculation of the interaction energy between B and H demonstrates that B and H repel each other. Consequently, B may block the site of occupation of H at the GB, and restrain the H-induced embrittlement. To understand the mechanism of the obtained energetic features, the electronic densities of states (DOSs) are calculated. A comparison of the total DOSs between the B-doped GB and undoped as well as H-doped ones shows that B increases the hybridization of the GB, which contributes to the enhanced binding of the B-doped GB over the undoped and H-doped ones. When the site of B changes from bulk to GB to surface, the hybridization between B and Ni decreases accordingly. It is proposed that the segregation behavior of B at the GB and surface is dominated by the competition between B(p)-Ni(d) bond energy and the strain energy induced by B. The preference of B for the Ni-rich interstice in Ni3Al is explained by the repulsive interaction between B and Al atoms resulting from the hybridization between their electrons when they are close to each other. The repulsion between B and H can also be explained by the same electronic structure mechanism as that for the B-Al interaction. The segregation of B at surface shifts the DOS of its nearest neighbor Ni to lower energy. This may increase the chemisorption potential energy of H2O on Ni3Al surface and, therefore, decrease the reactivity of the surface, inhibiting the environmental embrittlement of Ni3Al.
关键词:
intergranular fracture;environmental embrittlement;polycrystalline;ni3al;water dissociation;first-principles;metal-surfaces;boron;segregation;ductility;hydrogen
张善业
,
高怡斐
物理测试
对马钢生产的耐火H型钢MGFR490B和Q345B H型钢进行了对比试验研究,完成了高温拉伸和高温持久两项力学性能测试和对两种钢微观组织的观察研究.结果表明,耐火H型钢MGFR490B的组织为多边形铁素体+珠光体+少量贝氏体混合多相组织,此种组织在高温下能保持很好的稳定性,并能在高温下析出合金碳化物,这对降低耐火H型钢MGFR490B的室温屈强比和保持高温屈强比小的波动范围有益.耐火H型钢MGFR490B获得了比Q345B H型钢好的高温强度性能,这与耐火钢的混合多相组织及添加合金元素密不可分.耐火H型钢MGFR490B在600℃高温下能保持高的强度,并且其持久断裂时间超过3 h,满足耐火钢的性能指标要求.
关键词:
耐火钢
,
高温拉伸
,
高温持久
,
屈强比
张善业
,
高怡斐
物理测试
对马钢生产的耐火H型钢MGFR490B和Q345B H型钢进行了对比试验研究，完成了高温拉伸和高温持久两项力学性能测试和对两种钢微观组织的观察研究。结果表明，耐火H型钢MGFR490B的组织为多边形铁素体﹢珠光体﹢少量贝氏体混合多相组织，此种组织在高温下能保持很好的稳定性，并能在高温下析出合金碳化物，这对降低耐火H型钢MGFR490B的室温屈强比和保持高温屈强比小的波动范围有益。耐火H型钢MGFR490B获得了比Q345B H型钢好的高温强度性能，这与耐火钢的混合多相组织及添加合金元素密不可分。耐火H型钢MGFR490B在600 ℃高温下能保持高的强度，并且其持久断裂时间超过3 h，满足耐火钢的性能指标要求。
关键词:
耐火钢
,
high temperature tensile high temperature persistent
,
yield ratio
,
null
