| Nanocrystalline materials are3D solid materials with grain size ranging from lnm to100nm. They have a series of excellent physical, chemical and mechanical properties due to unique structures. They have gain widespread concern and further study on fabrication methods, materials properties and deformation mechanism.Nanocrystalline copper was fabricated successfully by dynamic plastic deformation under explosive loading(EDPD), and developed the following research. Firstly, based on different explosive loading, quantitative characterization of strain and strain rate under different charge thickness have influence on grain refinement. Secondly, from a macro perspective, the calculation model of macroscopic temperature rise was established based on the overall temperature rise mechanism caused by adiabatic shock compression under explosive loading. From a micro perspective, the polycrystalline copper model was created by Voronoi method and the calculation model of microscopic temperature rise was established based on grain plastic deformation heat. The grain thermal stability and the feasibility of nanocrystalline copper fabrication under explosive loading were discussed with high pressure melting point theory and grain growth theory. Finally, The evolution model of work hardening-dynamic recovery was established based on Kocks-Mecking-Estrin model and discussed the grain refining mechanism under explosive loading.The results show that it is propitious to grain refinement with greater strain and strain rate. The combined effect of the macro impact temperature rise and the micro local temperature rise would not cause grain growth rapidly. Through the transmission electron microscope(TEM) analysis, the main mechanism of grain refinement was interaction of dislocation motion and deformation twinning under explosive loading, to verify that the preparation of nanocrystalline cooper under explosive loading is feasibility and the thermal stability of grain refining. |
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