| As a kind of efficient, clean, sustainable and new energy, nuclear energy has obtained more and more attention. With the rapid development of nuclear power industry in China, the spent fuel output from the nuclear reactor is increasing day by day, together with the neutron absorbing materials employed for nuclear power plants in China are mainly imported, therefore, it is inevitable to develop a high performance neutron absorbing material for spent fuel storage. At present, localization of neutron absorbing materials remains an urgent problem to be solved. In this dissertation, we developed B4C/AI composites, one promising neutron absorption materials, through a facile and low cost press-vacuum sintering as well as rapid hot-pressing method based on powder metallurgy technology. The processes of press-vacuum sintering method and rapid hot-pressing method were systematically investigated, including phase composition, microstructure and mechanical properties. The results are as following:(1) As to B4C/AI composite prepared by press-vacuum sintering method, the density of green compaction increased with the augment of the pressure during the cold pressing process, which was in well agreement with typical pressing equations, especially with Huang Peiyun’s equation. The density of sintered body first increased and then kept steady with the increasement of sintering temperature, increased continually with the prolonging of the vacuum sintering during the vacuum sintering process. The density of the composite increased with the increasement of hot rolling temperature.(2) The B4C/AI composites prepared by press-vacuum sintering were pure phase with B4C and Al, no obvious defective phase AI4C3 was found. The relative density of composite with 36 wt% B4C reached maximum as high as 98.13% when prepared by 400 MPa cold press forming,2 hours vacuum sintering at 600 ℃, hot rolling at 500 ℃, and its bending strength reached 284 MPa and hardness was 71 HB. Fracture mechanism of the composite contained ductile fracture of aluminum alloy matrix and cleavage fracture of B4C particles, as well as interfacial debonding between B4C particles and aluminum matrix, indicating the coefficient result of various kinds of fractures.(3) The phase composition of B4C/Al composite prepared by rapid hot-pressing method was B4C and Al, with B4C particles uniformly embedded in Al matrix, and the interfaces between particles and matrix were well integrated. Moreover, the density of the composite increased with increasing cold pressing pressure and decreasing B4C content respectively. The co-effect of hot pressing pressure and temperature benefits the Al liquid fill in pores of the composite, thus resulting in high density. The relative density of composite with 30 wt% B4C reached maximum as high as 99.87% when prepared by 150 MPa cold press forming and 10 MPa hot pressing at 530 ℃. After T6 heat treatments, the hardness and bending strength of composite both enhanced and reached 123 HB,394 MPa respectively. The fracture mode of composite was ductile fracture before T6 heat treatment, and there’s a trend toward changing to brittle fracture after T6 heat treatment.(4) Press-vacuum sintering method has a high utilization rate of raw materials, less subsequent processing, as well as low production cost. Its process, however, is complex, including the following densification process. Moreover, the as-prepared composite size is small, therefore, it is appropriate for the production of component with exquisite shape. By contrast, the composite prepared by rapid hot-pressing method is much more compact, exhibiting a higher mechanical properties. In addition, hot-pressing method presents a more simple process and lower energy consumption, coupled with the hot rolling, it can apply to the production of large size composite sheet, but there is a higher requirement for hot pressing mould. |
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