Dejun Yu
材料科学技术（英文）
Nanolayered Cu-Nb composites offer a series of enhanced properties for their use in extreme conditions, e.g. high field magnets and high irradiation resistance. However, the stability of the Cu/Nb heterogeneous interface needs confirmation under various conditions. In the present work, molecular dynamics simulations were carried out to investigate the interfacial behavior under various temperatures with initial stress at the interface. It is found that the interface becomes unstable at simulation temperatures higher than 600 K, resulting in the emission of dislocations and loops within one or more slip systems. The emission process is found to be thermally-activated, i.e., the higher temperature, the shorter annealing time needed. The present study is
believed to assist the experimental synthesis of the Cu-Nb multilayer nanocomposites for multiple applications.
关键词:
Interface
Dejun Yu
材料科学技术（英文）
Nanolayered Cu-Nb composites offer a series of enhanced properties for their use in extreme conditions, e.g. high field magnets and high irradiation resistance. However, the stability of the Cu/Nb heterogeneous interface needs confirmation under various conditions. In the present work, molecular dynamics simulations were carried out to investigate the interfacial behavior under various temperatures with initial stress at the interface. It is found that the interface becomes unstable at simulation temperatures higher than 600 K, resulting in the emission of dislocations and loops within one or more slip systems. The emission process is found to be thermally-activated, i.e., the higher temperature, the shorter annealing time needed. The present study is
believed to assist the experimental synthesis of the Cu-Nb multilayer nanocomposites for multiple applications.
关键词:
Interface
Mohamed KHARRAT
,
Maher DAMMAK
,
Amine CHARFI
材料科学技术（英文）
Fibre-matrix interface is known to have contribution to the mechanical performance of fibre-reinforced composite by its potential for load transfer between the fibre and the matrix. Such load transfer is of great importance in dentistry when a post is used for fixing a ceramic crown on the tooth. In this study, a pull-out test was carried out to analyse the interfacial properties of a steel fibre embedded in a polyester and epoxy matrices. It was found that the fibre-matrix interface is debonded on the whole embedded length when the fibre stress reached the debonding stress. Then, the fibre stress fell down to the initial extraction stress required to pulling out the debonded fibre from the matrix. Both debonding stress and initial extraction stress initiated a linear increase with the implantation length after the debonding stress reached horizontal asymptotes. To analyse the fibre-matrix load transfer before debonding, an analytical shear-lag model was adopted to in this test conditions. Fitting the experimental results with the analytical model provided the interfacial shear strength. By considering the Coulomb friction at the fibre-matrix interface during the fibre extraction process, an analytical model which considers Poisson's effects on both fibre and matrix, was developed. In this model, knowledge of the initial extraction stress of the fibre provides the residual normal stress at the fibre-matrix interface.
关键词:
Fibre
,
null
,
null
,
null
,
null
,
null
,
null
Weimin MAO
,
Dong LI
材料科学技术（英文）
The image stress of straight screw dislocations parallel to the medium surface covered by thin heterogeneous films was analyzed and deduced, in order to calculate the image shear stress. The relationship between image stress and distance from the screw dislocation to the interface of pure aluminum and its oxide covering was calculated based on the analysis. It was shown quantitatively that a sign conversion of the image stress appears in the case of thin oxide covering, while dislocation would pile up near the interface because of the possible slips of the screw dislocations induced by the image stress, which might break down the very thin oxide covering. Further investigation on edge dislocations or other dislocation configurations need to be done.
关键词:
Dislocation
,
null
,
null
,
null
,
null
,
null
,
null
Nanlin SHI
,
Jiwei FENG
,
Yanfen GUO
,
Yuyin LIU
,
Z.X.Guo
材料科学技术（英文）
Prenitridation of the TiBx coating surface of the Sigma SM1240 SiC fiber can form more stable compounds at the surface and obstruct the release of boron atoms into the Ti-based alloy matrix. The effect of nitridation on the tensile strength of the fiber was investigated in this work. Nitridation could degrade the tensile strength of the SiC fiber if the treating temperature and time are not optimized. The chemical reaction between the W core and SiC and the modification of fiber microstructure during the nitridation are responsible for the degradation in strength. The strength can be maintained by further optimization of the treating temperature and time. Therefore, stabilizing the surface of TiBx coating and hence the interface of the SiCf/Ti composite by the nitridation of the SiC fiber is a feasible technique for practical applications.
关键词:
SiC fiber
,
null
,
null
,
null
,
null
Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The wetting behavior of molten Bi on polycrystalline Cu substrate and single crystal Cu substrate was studied by the sessile drop method in the temperature range from 673 to 873K. At low temperature the wetting behaviors of molten Bi on both types of Cu substrate were similar. However, at high temperature, the equilibrium contact angle of polycrystalline Cu substrate was lower than that of single crystal Cu substrate, because the preferred dissolution of grain boundaries leads to a smaller liquid/solid interfacial energy for polycrystalline Cu substrate. The formation mechanism of arrow-shaped Cu grains at the Bi/single crystal Cu interface is also discussed.
关键词:
Wettability
,
null
,
null
,
null
Kun LI
,
Nanlin SHI
,
Jun GONG
,
Chao SUN
,
null
,
null
,
null
,
null
材料科学技术（英文）
Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique. The fibres were pre-coated a SiO2 layer prior to fabrication. Different microstructures and interactions in the fibre-matrix interface of these composites were observed by transmission electron microscopy (TEM). The results showed that the interfacial interaction strongly depended on the content of Al in the Mg-based matrices. The microstructure of the interface could then be controlled by adjusting the Al content of the Mg-based matrix. In addition, fibres extracted from different Mg-based matrix all had some degradation owing to the interfacial reaction and the fibre-matrix interdiffusion.
关键词:
Carbon fibre
,
null
,
null
,
null
Honglian DAI
,
Xianying CAO
,
Haichen SHAO
,
Chunhua SHEN
,
Shipu LI
材料科学技术（英文）
Electron probe and X-ray energy spectrum were used to investigate the chemical composition of the interface between material and new bone after porous tricalcium phosphate ceramic implanted in tibia of rabbits. The element changes of the interface, the materials transformation and the situation of new bone formation at different implantation period were observed. The results showed that the carbon element content decreased gradually in new bone tissue, and the content of calcium and phosphor element increased by degrees with the implantation time. At the same time, calcium-phosphor ratio in the new bone kept a higher level. New bone grew into the materials interior, material dispersed and degraded simultaneously. Both composition of materials and new bone tended to be consentient. Finally, the materials were substituted by new bone. After implantation, not only the materials itself dissolved and degraded partially, but also new bone formed on the outer and pore surface of β-TCP porous bioceramics, which showed that the degradation products of lifeless calcium phosphate inorganic materials took part in constituting of new bone tissue.
关键词:
Calcium phosphate
,
null
,
null
,
null
Gang WANG
,
Dechang ZENG
,
Zhongwu LIU
金属学报(英文版)
The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled metallic melts with respect to undercooling was studied respectively based on two kinds of forms of local free energy density. The calculation results show that, with the increase of undercooling, the critical nucleus does not show bulk properties, and the nucleation barrier height decreases gradually and deviates more and more from that predicted by the classical nucleation theory in both cases. The physical spinodal occurs for a specific form of the local free energy density, where the nucleation barrier height vanishes when the undercooling reaches a critical value and the reduced nucleation barrier height can be expressed by a function of the ratio of undercooling to critical undercooling.
关键词:
Nucleation
,
null
,
null
,
null
