| B4CP/Al composites combine the excellent properties of B4C ceramic particle and aluminum alloy matrix,which has the advantages of high specific strength,high specific modulus,high temperature resistance,wear resistance and good neutron absorption capacity.These advantages make the B4CP/Al composites an ideal neutron-absorbing material.However,the preparation and processing technologies of B4CP/Al composites large-size plates have always been one of a difficulties that restrict the development of B4CP/Al composites.At present,the neutron-absorbing materials used in domestic nuclear power plants are basically imported from abroad.Therefore,in order to break the technical blockade of nuclear power key materials by developed countries and promote the safe and rapid development of nuclear power industry,the independent development of neutron absorption materials is imperative.In this paper,the B4CP/Al composite is taken as the research object,and related researches are carried out on several important aspects of the preparation and processing technologies of B4CP/Al composites large-size plates,including the hot deformation behavior,optimization of hot working technology,numerical simulation of rolling deformation process and microstructure and mechanical properties of rolling plates.The main conclusions can be made as following:A constitutive equation considering the effect of strain for predicting flow behavior of the B4CP/Al composite was conducted by isothermal single pass hot compression tests.The model can well predict the hot deformation flow behavior of B4CP/AI composite.The addition of B4C reinforced particles promotes the dynamic recrystallization behavior of the 34CP/Al composite.Dynamic recrystallization can occur at lower deformation temperatures and higher strain rates.As the deformation temperature increases and the strain rate decreases,the dynamic recrystallized grains grow continuously,and the average grain size and the ratio of the large-angle grain boundaries increase accordingly,and the dynamic recrystallization of the composite material is more sufficient.The critical conditions for dynamic recrystallization of B4CP/6061Al composites are:?c=0.8374?P-0.33708,?c=2.39×10-4Z0.11022.Processing maps based on Dynamic Material Model of B4CP/Al composite have been established.The flow instability zones of B4CP/6061Al composite are mainly located in the high strain rate region,the low temperature with low strain rate region and the intermediate temperature with low strain rate region(when the strain is 0.7).Typical microstructural features in the instability zone are agglomeration of B4C particles,fracture of B4C particles,formation of voids,and abnormal growth of dynamic recrystallized grains.Reasonable processing parameters for good workability for 25vol.%B4CP/AA 6061 composite are obtained in the temperature range of 450?-500? and strain rate range of 0.01s-1-0.1 s-1.Thermal-mechanical coupling finite element analysis of different workpiece structures and different rolling technologies of B4CP/6061Al composite were carried out using commercial finite element simulation software.Simulation results show that,fully covered package could improve the uniformity of the temperature field,stress field and strain field distribution of B4CP/6061Al composite.The introduction of the fully covered package can effectively prevent surface cracks and edge cracks during rolling process.Rolling temperature and rolling speed have significant effects on the distribution of temperature field and stress field during the rolling process of B4CP/6061Al composite.As the rolling temperature reduced from 500 ? to 470 ?,the surface temperature drop gradually increases.When rolling temperature belows 480 0C,the lowest temperature is beyond the hot working temperature scope of B4CP/6061Al composite.As the rolling speed increased from 0.1 m/s to 0.3m/s,the surface temperature drop gradually decreases,but the fluctuation range of effective stress and shear stress gradually increases.Reasonable rolling parameters for B4CP/6061Al composite are:fully covered package with rolling temperature of 500? and rolling speed of 0.2m/s. |
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