J.H Lee
,
J. Chen
,
S.J. Choe
,
Y.T. Lee and H.M. Kim(High Temperature Materials Laboratory
,
Korea Institute of Machinery & Materials
,
66 Sangnam Dong
,
Changwon
,
Kyungnam
,
641010
,
Korea Manuscript received 26 August 1996)
金属学报(英文版)
The carbide growth behavior of MAR-M247 LC alloy was investigated by directional solidification and quench method. The carbide volume fraction, trapping and growth behavior were correlated with the growth rate.It was found that the carbide volume fraction decreased at slower growth rate.This decreasing was caused by lower solidliquid interface trapping ability at slower growth rate.
关键词:
:carbide
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null
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null
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null
ZENON OPIEKUN
金属学报(英文版)
The manuscript presents changes of macrostructure and microstructure of plate and shaft castings made of cobalt alloy MAR-M509. They have different values of geometric module M within the range of 0.91-5.56 mm that have been created with multilayer ceramic shell moulds (MSC) of different initial temperatures of 200-1000℃ at the moment of pouring. It has been stated that decrease of initial temperature of MSC and value M causes increase in casting fine-granularity, distance reduction between dendrite branches λ2 and refinement of initial carbides in irregular ternary eutectic γ+$M23C6+MC.
关键词:
Multilayer ceramic shell mould (MSC)
ZHENG Yunrong
,
WANG Luobao
,
LI Chenggong Institute of Aeronautical Naterials
,
Beijing
,
China. To whom correspondence should be addressed.
材料科学技术（英文）
Hf lowers the incipient melting temperature of superalloy. As carbon content in Hf-bearing alloy decreases, the incipient melting temperature drops furthey. PD ingots have stronger tendency to incipient melting than HRS ones. Even though in PD ingot, the sensitivities at both ends of the ingot are quite different. The melting of Ni_5Hf phase may be considered as one of the main factors affecting incipient melting. The more Ni_5Hf the alloy contains, the more serious the incipient melting becomes. The results of differential thermal analysis (DTA) have proved that the peak of 1135-1160℃ corresponds to the melting range or Ni_5Hf. By means of a pretreatment at 1150℃, 8h, Ni_5Hf phase can be eliminated in two ways: the reaction Ni_5Hf+γ(C)→MC_(2)+γ and solid solution, and therefore the final solid solution treatment can be carried out at 1260℃. This brings about a high homogenized structure and further increases the stress rupture properties of the alloy at 1040℃, 140 MPa.
关键词:
DS superalloy
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null
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null
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null
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null
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null
ZHANG Shaoqing TAO Chunhu Institute of Aeronautical Materials
,
Beijing
,
China.
材料科学技术（英文）
The quench transfomation in a Ti-10V-2Fe-3Al near B-titanium alloy was studied by means of X-ray diffraction, transmission electron microscopy, and optical micyoscopy. The quenching temperatures were above and below the β transus temperature. The phase constitutions of specimens quenched from various solution temperatures were identified and the phase morphologies were examined. In addition, the relationship between phase lattice parameters and quenching tempera- tures was given for α, β and α ~(11) phases. This alloy has a tendency of precipitation of athermal ω phase and formation of stress induced α~(11) mar- tensite from β phase during quenching. Quenched from the temperatures above the β transus tem- perature, the alloy mainly consists of β phase, a small amount of α~(11) martensite and athemal ω phase aye also present in the alloy. After quenching from the temperatures below the β transus temperature, the α phase appeays in the alloy in addition to the phases mentioned above.
关键词:
β-titanium alloy
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null
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null
刘源
,
于金江
,
徐岩
,
孙晓峰
稀有金属材料与工程
研究了3种不同镍基高温合金在不同的热循环温度下的热疲劳性能.结果表明,单晶高温合金具有较好的热疲劳抗性,分别用光学显微镜和扫描电镜对热疲劳裂纹的萌生和扩展行为进行观察发现,裂纹首先在缺口处萌生,而在不同合金中裂纹的扩展行为具有显著差异.在单晶高温合金中裂纹的扩展方向与枝晶生长方向成45°,而在Mar-M002多晶定向合金中,裂纹则主要沿着枝晶间区域的共晶和碳化物进行扩展.扩展方式的不同对合金的热疲劳抗性会产生很大的影响.
关键词:
单晶高温合金
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热疲劳
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裂纹萌生和扩展
余天
,
李定国
,
李杏清
,
高春红
,
吕铃
,
郝身芬
,
王良民
,
张兆刚
,
陈鹏
材料导报
介绍了近年国际上在π共轭有机半导体中新发现的有机磁电阻效应(Organic magnetoresistance,O-MAR)实验和理论的研究进展,展望了有机磁电阻效应的应用和研究.有机磁电阻效应不仅具有各向同性、常温下大磁电阻率和高磁场灵敏度的特点,而且不同于传统的磁电阻效应和目前广泛研究的巨磁电阻效应(Giant magnetore-sistance,GMR),其结构中不包含磁性材料也没有外部极化自旋的注入,是有机半导体的一种内禀性质.
关键词:
π共轭有机半导体
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磁电阻效应
,
有机磁电阻效应
W.H. Tian
金属学报(英文版)
Microstructural variations and correlated hardness changes in B2-ordered NiAl containing fine precipitation of Ni2AlTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L21-type Ni2AlTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2AlTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2-ordered NiAl was investigated by compression tests over the temperature range of 873-1273K. The fine precipitation of Ni2AlTi was found to enhance greatly the yield strength and the high-temperature strength is comparison with that of superalloy Mar-M200.
关键词:
NiAl intermetallics
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null
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null
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null
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null
