A.Cantarel
,
E.Lacoste
,
O.Mantaux
,
E.Arquis
,
M.Danis
材料科学技术（英文）
Injection of liquid alloy through a fibrous preform located in an initially preheated mould is a classical method used to process metal matrix composites (MMCs). In order to reduce the chemical reactions between the fibres and the metal matrix, the fibrous reinforcement and the mould are commonly preheated up to initial temperatures much lower than the metal solidification temperature. Therefore, metal solidification instantaneously occurs on fibre contact during composites infiltration. Unlike what happens when infiltrating a pure metal, temperature and composition are able to vary within the matrix; these heterogeneities induce macrosegregation within composites...
关键词:
Segregation
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null
,
null
Shenhua SONG
,
R.G.Faulkner
,
P.E.J. Flewitt
,
Dongdong SHEN
,
Jing LIU
,
Zexi YUAN
材料科学技术（英文）
Irradiation-induced impurity segregation to grain boundaries is one of the important radiation effects on materials. For this reason, phosphorus segregation to prior austenite grain boundaries in a P-doped 2.25Cr1Mo steel subjected to neutron irradiation is examined using field emission gun scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis (EDX). The steel samples are irradiated around 270 and 400℃, respectively. The irradiation dose rate and dose are ～1.05×10-8 dpa/s and ～0.042 dpa respectively for 270℃ irradiation, and 1.7×10－8 dpa/s and 0.13 dpa respectively for 400℃ irradiation. The FEGSTEM results indicate that there is no apparent phosphorus segregation during 270℃ irradiation but there is some during 400℃ irradiation
关键词:
Neutron irradiation
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null
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null
,
null
S.H. Song
,
null
金属学报(英文版)
Embrittlement of a 2.25Cr1Mo steel stemming from neutron irradiation at 270oC is studied by virtue of small punch testing in conjunction with scanning electron microscopy. The ductile-brittle transition temperature determined by the small punch test is much lower than that determined by the standard Charpy test. There is some irradiation-induced embrittlement effect after the steel is irradiated for 46 days with a neutron dose rate of 1.05?0-8 dpa/s.
关键词:
Irradiation
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脆性
,
偏聚
,
低合金钢
,
压力容器
孙大鹏
,
赵永慧
,
苏海燕
,
李微雪
催化学报
doi:10.1016/S1872-2067(12)60604-4
采用从头算原子热力学方法系统研究了Ni-rich和Pt-rich条件下Pt3Ni(111)在不同偏析、表面化学吸附氧覆盖度下560个可能结构的相对稳定性,构建了氧气气氛下Pt3Ni(111)表面结构演化、直至满覆盖化学吸附氧的热力学相图.结果表明,随着氧的化学势的升高,在热力学上仅出现两类稳定的结构,主要包括没有化学吸附氧的干净Pt-skin表面,以及在很低氧的化学势下就形成自含有化学吸附氧的Ni-skin表面,而有化学吸附氧的PtNi表面合金化的中间结构则处于亚稳态.仔细分析发现,这些结构的形成主要由金属的偏析能、氧与两种金属成键强弱的差别、氧的化学势的高低三个因素共同决定.
关键词:
Pt3Ni
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氧气
,
偏析
,
相图
,
从头算
Shenhua SONG
,
Luqian WENG
材料科学技术（英文）
Quenching-induced phosphorus segregation to prior austenite grain boundaries in a 0.077 wt pct P-doped 2.25Cr-1Mo steel is examined using field emission gun scanning transmission electron microscopy (FEGSTEM). A phosphorus level of around 1.56 at. pct is observed for the water-quenched sample. In recognition of insufficiently high spatial resolution of the technique for grain boundary composition analysis, the measured results are corrected by an analytical convolution method. The corrected phosphorus segregation level may be up to about 4.7 at. pct. The quenching-induced phosphorus segregation is nonequilibrium segregation and the migration of vacancy-phosphorus complexes plays an important role in the kinetic process. For such a reason, the mechanism for migration of the complexes is discussed in some detail.
关键词:
Grain boundary
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null
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null
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null
