ZHAI Qijie HU Hanqi University of Science and Technology Beijing
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China associate professor
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Faculty of Foundry
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University of Science and Technology Beijing
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Beijing 100083
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China
金属学报(英文版)
Effect of nitrogen on matrix structure of 3 different varieties of gray cast iron,i.e., sub-eutectic Fe-C-Si,near-eutectic Fe-C-Si and Fe-C-Si-Mn,has been investigated. The eutectie colony structure of gray cast iron may be refined,the pearlite content increased and the micro-hardness of pearlite and ferrite raised with an addition of nitrogen.The influ- ence of nitrogen on the transformation temperature of the equilibrium and non-equilibrium phases,as well as,the solution of nitrogen in ferrite and cementite seem to be the major rea- sons to strengthening the matrix structure of gray cast iron.
关键词:
nitrogen
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null
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null
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null
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null
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Specimens of an Fe-Cr-Mn-N dual-phase stainless steel were solution treated at 1050 and 1250-degrees-C, yielding grain sizes of 10 and 32-mu-m respectively. Low cycle fatigue tests at constant total strain amplitude ranging from 4 x 10(-3) to 1.2 x 10(-2) were carried out at room temperature in air. The cyclic stress response, hysteresis loss per cycle and dislocation structure were investigated in the course of the cyclic deformation. No significant differences were noted in either the cyclic behaviour or the dislocation structure between the two heat treatment conditions. Cyclic hardening occurred in the very early stage of fatigue life. After passing through a maximum of hardening, cyclic softening set in until fracture. The strain amplitude affects the initial hardening rate and hysteresis loss. Dislocation tangles and planar arrays of dislocation were observed after the first few cycles in the initial hardening stage, while the cyclic softening stage is characterized by the formation of irregular bands or wall structures. In addition, grain boundaries were found to be effective barriers to slip dislocations during the initial hardening stage, while increased relaxation activities at grain and twin boundaries are evident during the cyclic softening stage. The present observations suggest that the dislocation activities within the grains and at or near the grain boundaries are both responsible for the observed cyclic hardening and softening of the material under study. The failure mode for the specimens solution treated at 1050-degrees-C was transgranular while that at 1250-degrees-C was intergranular. The former has a fatigue life about twice that of the latter under identical total strain amplitude.
关键词:
nitrogen
A. Mitchell
金属学报(英文版)
Nitrogen has a significant effect on superalloy mechanical properties, almost without exception in a negative sense. All of the alloys contain strong nitride formers (Ti, V, Nb, Hf, Ta) and will, because of the nitride-former concentration, produce nitride precipitates not only during solidification but also when the alloy is fully liquid and significantly superheated. In this review we present an examination of the problems involved in removing nitrogen from the alloys and also of the mechanisms by which nitrides influence mechanical behaviour. It is concluded that one of the most effective means of control of the nitrogen content lies in the choice of raw materials for the alloy make-up, but that the subsequent nitride formation can be minimised by correct choice of process routes in VIM, ESR, VAR and EBCHM.
关键词:
nitrogen
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null
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金属学报
doi:10.3321/j.issn:0412-1961.2003.11.006
根据有关术语、实验结果和理论处理方法的现有数据,对冷加工峰,200,220或250℃峰,Snoek-Koster(SK)峰,以及Snoek-Ke-Koster(SKK)峰进行了评估.并特别强调了葛庭燧教授(Ke)为理解冷加工峰所作的贡献.同时,对由(1)Schoeck,(2)Seeger,(3)王业宁等人,(4)Magalas 和Ngai,以及(5)Ogurtani等人发展的现有理论模型进行了简要的综述.
关键词:
Snoek-Koster峰
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冷加工峰
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Snoek弛豫
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Cottrell气团
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葛庭燧
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内耗
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机械波谱学
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位错
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固溶体
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铁
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碳
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氮
于燕鹏
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胡少成
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马红权
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吴振宁
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黄小峰
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胡学强
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王蓬
冶金分析
doi:10.13228/j.issn.1000-7571.2014.10.006
在脉冲加热红外吸收热导法测定钢铁材料中氧氮系列研究的基础上,通过对仪器分析气路的快速转换,实现了单台仪器快速测定氧氮和氢3种气体元素.实验主要对测氢的脉冲加热条件、助熔剂和坩埚的影响等进行考察,确定分析功率为2 300 W、加1片锡片助熔、使用套坩埚为氢测定的最佳分析条件.通过对氧、氮和氢标准样品的测定,建立了方法的校准曲线.利用对空白的标准偏差计算得氧氮和氢的检出限分别为0.000 027％、0.000 021％和0.000 015％,氧氮分析范围为0.000 09％～0.2％和0.000 07％～0.2％,氢的分析范围为0.000 05％～0.05％.对氧、氮和氢含量较低的钢标准样品进行精密度考察,结果的相对标准偏差(RSD,n=11)均小于5％;用于钢铁实际样品的测定结果与其他仪器所得结果一致,完全满足钢铁材料中气体元素的分析要求.
关键词:
脉冲加热
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熔融
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红外吸收法
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热导法
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钢铁
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氧
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氮
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氢
高再玲
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赵霞
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刘栓
电镀与涂饰
通过溶胶-凝胶法制备了N掺杂TiO2纳米颗粒(N/TiO2),采用X射线衍射仪和透射电镜对其进行了表征,并与醇酸树脂混合制成纳米N/TiO2复合醇酸树脂涂层.采用盐雾试验、动电位极化曲线和电化学交流阻抗技术研究了纯醇酸树脂涂层和纳米N/TiO2复合醇酸树脂涂层在海水环境中对碳钢的防护性能.结果表明:N/TiO2粉末的晶型为锐钛矿型,粒径及结晶度均低于纯TiO2.在醇酸树脂中添加1％的纳米N/TiO2,所得复合涂层可有效抑制海水在其中的扩散,显著提高了醇酸树脂涂层的耐蚀性:耐盐雾时间从480 h提升到900 h;在相同的浸泡时间内,0.01 Hz时的阻抗模值均高于醇酸树脂涂层;自腐蚀电位正移.
关键词:
醇酸树脂
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二氧化钛
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氮
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掺杂
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溶胶-凝胶法
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碳钢
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海水
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腐蚀防护
SHANG Yuhua XU Leying Institute of Metal Research
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Academia Sinica
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Shenyang
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China SHANG Yuhua Senior Engineer
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Institute of Metal Research
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Academia Sinica
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Shenyang 110015
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China
金属学报(英文版)
Deducting interference method was applied to determine the concentration of nitrogen in the presence of Ti.This procedure is available in treating the interference of same order diffraction in EPMA.
关键词:
interference
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null
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null
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ZHAI Qijie
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HU Hanqi
,
University of Science and Technology Beijing
,
Beijing
,
China HU Hanqi
,
Professor
,
Faculty of Foundry
,
University of Science and Technology Beijing
,
Beijing 100083
,
China
金属学报(英文版)
The expressions of the dependence of nitrogen solubility in molten gray cast iron on the temperature and composition of the melt were proposed under the condition of foundry practice. Three gray cast iron specimens with different compositions were examined in good agreement with the derived expression.
关键词:
gray cast iron
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null
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