J.H. Byun
,
S.-K.Lee and B.S. Kim (Korea Institute of Machinery and Materials
,
P.O. Box 41
,
Changwon
,
Korea Manuscript received 26 August 1996)
金属学报(英文版)
In order to realize the potential of composite materials, it is imperative to develop a manufacturing process, to understand the microstructures, and to assess the structural performance of the composite. The braided-pultrusion process, which combines the pultrusion process with the braiding technology, has been developed by utilizing a novel resin impregnation device. The goal of the development is to achieve both costeffectiveness and performance of the composite. The tubular composites of diameter 5.3 mm have been produced using Kevlar 49 fiber and polyester resin. In order to assess the mechanical performance of the composites, an analytical method for predicting the elastic constants has been developed. The analysis includes the geometric model of a unit cell, coordinate transformation, and averaging of stiffness and compliance constants of the constituent materials. The analytic predictions compared favorably with experimental results.
关键词:
: braided pultrusion
,
null
,
null
孙长征
,
宇波
,
魏进家
工程热物理学报
通过分析气相、液相、管壁之间的关系,将气液混输管道中的流型划分为五种,并总结了各流型的特点及气液相和管壁间的几何关系;在对Baker、Brill、Beggs-Brill、Taitel、段塞特征分析(SCA)等流型判别方法进行分析的基础上,提出了一种综合使用SCA、Taitel和Brill三种方法的流型判别方法 S-T-B法.经算例验证,该方法对气液两相混输的流型判断准确性较高,可以作为气液混输工艺计算过程中确定流型的方法.
关键词:
气液混输
,
流型
,
段塞特征分析法
,
S-T-B
材料科学技术（英文）
Creep testing was conducted on K40S alloy. The detailed creep deformation and fracture mechanisms under constant load were studied. The results show that the stress exponent ranges between 7 and 14.4 at elevated temperature 973similar to1173 K, and that the activation energy is approximately 449.1 kJ/mol. During creep, the grain boundary sliding cut off primary carbides at the boundary, generating the "O" model cracks. The creep failure mode of K40S alloy is transgranular ductile and cracks originate at the primary carbides. A long carbide and matrix interface is often a preferential path for crack propagation. The creep mechanism is discussed in light of the creep microstructure, the stress exponent and the activation energy.
关键词:
K40S alloy;creep;fracture;crack propagation;activation-energies;superalloy;term
王宝奇
,
谷南驹
,
郭素珍
,
马晓莉
金属学报
利用Bain点阵对应对K-S模型的晶格改建过程进行了严密的数学描述.对于不同的马氏体正方度,提出了计算第一切变、第二切变及晶格调整的计算依据,并给出了普遍的计算公式.以Fe-1.4C和纯铁为例,计算了马氏体相变的点阵畸变.进一步分析表明,K-S模型实质是Bain模型的旋转.计算的结果与实测的取向关系相符合.
关键词:
K-S模型
,
null
,
null
Materials Letters
Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
M6C precipitation;aging;M7C3 carbide;superalloy
材料科学技术（英文）
The doping of phosphorus, sulfur and boron in IN718 superalloy can remarkably influence the creep behavior. The modifications of the minor elements seem not to vary the stress exponent and the influences primarily concentrate on the effective diffusion coefficient. A pronounced beneficial interaction between P and B and a weaker detrimental interaction between P and S have been obtained. The preexponential frequency constant is proved to be strongly related with the creep activation energy because of the so-called compensation effect. The compensation temperature has been determined to be about 1080 K, which corresponds to the transformation temperature from rapidly coarsened gamma " phase to delta phase. It has been proposed that trace elements can influence the effective diffusion coefficient individually or cooperatively, which in turn either retard or speed the creep process.
关键词:
Materials Letters
Low cycle isothermal mechanical fatigue testing K40S cobalt-base superalloy was carried out at 700 and 900degreesC with total strain amplitude from +/-0.1 to +/-1.0 pct. Correlations between microscopic cyclic deformation and cycle stress response with various microstructural phenomena were enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), detailing the deformation substructure and carbide precipitation. The results show that K40S superalloy exhibited cyclic stress response of cyclic hardening at 700degreesC, and of initial hardening followed by softening at 900degreesC. In addition, at both temperatures, cyclic hardening during cycle deformation increased with increasing strain amplitude, while the fatigue lifetime decreased. The cyclic stress response behavior can be rationalized based on the mechanisms associated with dislocation-dislocation interactions, dislocation-precipitate (M23C6) interactions and interactions between solute atoms and dislocations. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
K40S cobalt-base alloy;isothermal cyclic deformation;cyclic stress;response;room-temperature;behavior;alloy;mechanisms
