Guangye ZHANG
,
Xinghao DU
,
Jianting GUO
,
Hengqiang YE
材料科学技术（英）
Brittle-to-ductile transition (BDT) behavior and creep behavior of extruded NiAl-25Cr alloy at elevated temperatures were investigated. The results reveal that the alloy exhibits obvious BDT behavior with the increase in temperature and BDT temperature (BDTT) is sensitive to initial strain rate. When the initial strain rate increases by two orders of magnitude, BDTT has an increase of approximate 80 K. The creep data in the temperature range of 1073～1123 K reveal two distinct regions of creep behavior in this material. At lower temperature, the creep characteristics are consistent with structural controlled creep process where creep deformation is controlled by dislocation climb. At higher temperature, the creep characteristics are consistent with mobility-controlled deformation where viscous glide of dislocations controls creep. The apparent activation energy determined by creep in both regions exceeds the value for lattice self-diffusion in NiAl by a considerable amount. This can be explained in terms of the simultaneous deformation of second phase particles (γ'-Ni3Al and α-Cr phase) along NiAl matrix during creep.
关键词:
NiAl
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null
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null
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null
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null
Limin LIU
,
Shaoqing WANG
,
Hengqiang YE
材料科学技术（英）
The interface structure, work of adhesion, and bonding character of the polar TiC/Ti interface have been examined by the first-principles density functional plane-wave pseudopotential calculations. Both Ti- and C-terminated interfaces including six different interface structures were calculated, which present quite different features. For the Ti-terminated interface, the interfacial Ti-Ti bond has a strong metallic and weak covalent character; while for the C-terminated interface, the interfacial bond is a strong polar covalent interaction between the Ti-3d and C-2p orbital. The work of adhesion of C-terminated interface is nearly 9 J/m2 stronger than that of the Ti-terminated. It is found that each termination has relatively large work of adhesion, which is consistent with other polar interfaces.
关键词:
First-principles
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null
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null
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null
Jiuzhou ZHAO
,
Dongming LIU
,
Hengqiang YE
材料科学技术（英）
In order to understand the solidification process of an atomized droplet and predict the fraction solidification of droplets with flight distance during spray forming, a numerical model based on the population dynamics approach is developed to describe the microstructure evolution under the common action of the nucleation and growth of grains. The model is coupled with droplets heat transfer controlling equations and solved for Al-4.5~wt~pct Cu alloy. It is demonstrated that the numerical results describe the solidification process well.
关键词:
Rapid solidification
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null
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null
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null
Chiwei LUNG
,
Enke TIAN
,
Hengqiang YE
材料科学技术（英）
Introducing the stress distribution near grain boundaries to improve the dislocation pileup model for the Halt-Petch (H-P) relation, the continuous distribution of dislocations in the pileup could be solved by means of Tschebysheff polynomials for the Hilbert transformation. An analytical formula of the stress intensity factor for the dislocation pileup is obtained. The reverse H-P relation may be explained by the modified dislocation-pileup-model.
关键词:
Shouliang BU
,
Shaoqing WANG
,
Hengqiang YE
材料科学技术（英）
It is shown that synchronization, in a weak sense, can be achieved between two-parameter non-matching systems by using the adaptive control method. In essence, this requires just a scalar signal transmitted from the drive to the response system. Two typical chaotic systems, i.e., Lorenz and Rőssler system, are taken as examples of applications in this paper.
关键词:
Chaotic systems
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null
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null
