NIU Yan
,
F.GESMUNDO
,
WU Weitao
,
ZENG Chaoliu
,
F.VIANI
,
(State Key Laboratory for Corrosion and Protection
,
Institute of Corrosion and Protection of Metals
,
Chinese Academy of Sciences
,
Shenyang.110015
,
China)(Istituto di Chimica
,
Facolta'di Ingegneria
,
Universita'di Genova
,
Fiera del Mare
,
Pad.D
,
16129 Genova
,
Italy)Manuscript received 3 July 1995
金属学报(英文版)
The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to sulfur attack at high temperatures.The alloy is nearly single-phase.containing mostly the intermetallic compound Co17Y2 plus a little amount of the solid solution of Y in cobalt.At 600-700℃ and at 800℃ under 10-2 Pa of S2 the alloy forms multi-layered scales consisting of an outer region of pure cobalt sulfide,an intermediate region of a mixture of the sulfides of the two metals and finally an innermost layer of a mixture of yttrium sulfide with metal cobalt.At 800℃ under 10-3Pa of S2,below the dissociation pressure of cobalt sulfide, the alloy forms only a single layer composed of a mixture of metallic cobalt with yttrium sulfide.Pure Y produces only the oxysulfide Y2O2S, as a result of the good stability of this compound and of the presence of some impurities in the gas mixtures used The corrosion kinetics is generally rather complex and irregular except al 800℃under 10-3 Pa of S2.The addition of yttrium always reduces the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of yttrium sulfide is never achieved.The internal sulfidation of Y in Co-15% Y is not associated with a depletion of Y in the alloy.This kind of diffusionless internal attack is typical of alloys with a very small solubility of the most reactive component Y in the base metal A.which restricts severely the Y flux from the alloy towards the alloy-scale interface.
关键词:
:cobalt-yttrium alloy
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WANG Huaming JI Jialin ** Institute of Metal Research
,
Academia Sinica
,
Shenyang.110015
,
China.*** Department of Mechanical Engineering
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China.To whom correspondence should be addressed.
材料科学技术（英文）
To bring the excellent abrasion-resistant po- tential of carbide into full play,composites of cast tungsten carbide(CTC)grains based on mainly plate martensite and high Cr,W white cast iron are made on substrate of grey iron by cast-in-place hardfacing process.Results of high-stress two-body and three-body abrasion show that:(1) Base alloy microstructures have overwhelming dominating effects on abrasion resistances of the composites in two-body and especially three-body abrasion systems.(2)All composites have very ex- cellent abrasion-resistances which increase drasti- cally with the increase of CTC grain size.In case of the same CTC grain size,composite based on martensite white cast iron is much more wear-resistant than that based on mainly plate martensite although the volume fraction of CTC grains in the latter is considerably larger than that in the former.In three-body abrasion system,load has little effect on wear rate for composites based on martensite white cast iron,but wear rate of conventional wear-resistant materials increases linearly in a very steep slope as the nominal stress increases.
关键词:
abrasion
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WANG Zhongguang SUN Zhengming YU Weicheng ** State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang.110015
,
China+ To whom correspondence should be addressed
材料科学技术（英文）
Based mainly on the work done at the authors' laboratory in recent years,this paper examines what is currently known about the cyclic deformation and fatigue properties of metal matrix composites, with particular emphasis on discontinuous fiber (whisker or particulate)-reinforced Al composites. The following items are discussed:fatigue strength and life,cyclic deformation and microstructural evolution,microcrack initiation and growth,fatigue crack propagation behaviour.
关键词:
metal matrix composite
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null
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YAO Daping CHEN Wenxiu Institute of Metal Research
,
Academia Sinica Wenhua Rd.
,
Shenyang.110015
,
China
材料科学技术（英文）
An investigation of the phenomenon of hydrogen trapping at grain boundaries in 18 Ni maraging steel has been carried out by the thermal hydrogen evolution technique.Grain boundary on- ly acts as a trapping site of hydrogen at low temper- ature region,and the peak of its hydrogen evolution from it is observed at 405K with 3.00K/rain heat- ing rate and with specimen of 0.55mm thick.The trap activation energy of hydrogen escaped from grain boundary is estimated as 14.2kJ/mol. Hydrogen trapping at grain boundary is mainly as sociated with segregated hydrogen by impurities, and its behaviour is primarily the interaction be- tween hydrogen and the hydrostatic stress field of the grain boundary.
关键词:
hydrogen trapping
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