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1.
We report on the novel application of nanoscratch characterization to provide insight into the plasticity mechanisms responsible for the behaviour of composites. Accordingly, we conduct deformation characterization with nanoscratch testing (DCNT) to study the deformation behaviour of two B4C reinforced ultrafine grained Al alloy tri-modal composites with average B4C particle sizes of ~1–6?μm and ~500?nm, respectively. To highlight the type of mechanistic information revealed in a DCNT study of composites, we concentrate on the influence of B4C particle size on deformation mechanisms.  相似文献   

2.
In this study, Grf/Al composite was fabricated by liquid pressure method. The diffusion layer and the nucleation and growth of Al4C3 were observed at the interface of Grf/Al composites by TEM and HRTEM. The growth mechanism of Al4C3 was analyzed in detail by crystallography theory. It was found that Al4C3 had no phase relations with the carbon fiber. (0 0 0 1) layer of Al4C3 was parallel with main growth direction. Both the diffusion layer at the interface and crystal structure of Al4C3 affected the shape of Al4C3. At a certain position, Al4C3 could connect two fibers when the fibers were close to each other.  相似文献   

3.
Aluminum metal-matrix composites (MMCs) show great potential for aircraft industries. Nevertheless, the composites can be affected by different forms of corrosion such as pitting and galvanic corrosion. A pulsed YAG laser installation was used to produce surface treatment on Al18B4O33w/2024Al composite. Results indicate that laser power has significant influences on both of the microstructure and the corrosion resistance. The difference in morphological transformations was observed on the surfaces of the laser-treated specimens. An increase in Epit was obtained after laser treatment for the composite. The improvement was considered primarily due to the reduction both of reinforcement Al18B4O33 whisker and intermetallics CuAl2 on the surfaces of the laser-treated composites, which were found to be sites for pits nucleation. Moreover, the specimen with 700 W laser treatment exhibited a much greater resistance to corrosion than the other specimens with laser treatment. This was attributed to the formation of the homogeneous and defect free microstructure in the laser-modified layer.  相似文献   

4.
By simulating the electron paramagnetic resonance (EPR) and optical spectra on the basis of the 120×120 complete energy matrix, this paper determines the local lattice structure parameters R1 and R2 for MCl:V2+ (M=Na, K, Rb) systems at 77 K, 195 K and RT (room temperature 295 K or 302 K), respectively. The theoretical results indicate that there exists a compressed distortion in MCl:V2+ systems. Meanwhile, it finds that the structure parameters R1, R2 and |△R| (= R1-R2) increase with the rising temperature. Subsequently, from the analysis it concludes that the relation of EPR parameter D vs.△R is approximately linear. Finally, the effects of orbital reduction factor k on the g factors for the three systems have been discussed.  相似文献   

5.
By analyzing the EPR spectra of Fe3+ ion in the fluorinde glasses, the local lattice structures around impurity Fe3+ ion in MF3:Fe3+ (M=Al, Ga) systems have been studied by means of diagonalizing the complete energy matrices of the electron-electron repulsion, the ligand-field and the spin-orbit coupling for a d5 configuration ion in a trigonal ligand-field. Both the second-order and fourth-order EPR parameters D and (aF) are taken simultaneously in the structural investigation. The results indicate that the local lattice structure around octahedral Fe3+ center has an expansion distortion for Fe3+ in MF3:Fe3+ (M=Al, Ga). The expansion distortion may be ascribed to the fact that the radius of Fe3+ ion is larger than that of Al3+ ion and Ga3+ ion, and the Fe3+ ion will push the fluoride ligands upwards and downwards, respectively. The local lattice structure parameters R=1.927 A, θ=55.538° for Fe3+ in AlF3:Fe3+ and R=1.931 A, θ=56.09° for Fe3+ in GaF3:Fe3+ are determined, respectively, and the EPR spectra of the MF3:Fe3+ (M=Al, Ga) systems are satisfactorily explained.  相似文献   

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