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| Distribution uniformity control of the aluminum matrix composite shielding materials with high tungsten concentration |
| HE Xueyi，SUN Changlong，WANG Meiling，WANG Zhanming，GAO Yuyang |
| （Nuclear Power Institute of China, Chengdu 610213, China） |
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Abstract The development of high-performance combined shielding materials is of great importance for the safe
operation of nuclear installations. In recent years, the aluminum matrix composite materials have attracted tremendous
interest with good mechanical properties, easy processing and corrosion resistance. Through the introduction
of tungsten- and boron-containing components, the aluminum matrix composites could meet the shielding requirements
for neutron and γ -ray radiation in different occasions. However, the composite materials generally suffer
from poor distribution of the components due to their density difference. For developing high-performance shielding
composite materials, it is crucial to establish the control means toward the uniform distribution of compositions
within the materials. In this study, using tungsten and boron carbide as the shielding components, the aluminum matrix
composites with high tungsten concentration (84%) were prepared by the powder metallurgy method. For the
mixing process of the ternary system, the impacts of the blending method and particle sizes of the raw powders
were investigated on distribution uniformity of the components. Within the composite systems, the macroscopic
dispersion of the tungsten powders was investigated through the X-ray fluorescence analysis. While the microscopic
dispersions of the components were characterized by scanning electron microscope and metallographic analysis.
Through cold isostatic pressing, followed by vacuum sintering and rolling process, composite sheets were also prepared
from the mixed powders and characterized to study the influence of distribution uniformity on microstructure
and mechanical strength of the materials.The results show that, compared to ball mixing, three-dimensional blending effectively reduces the breaking effect of the mixing process on tungsten particles and thus avoids the microscopic
aggregation of small particles within the materials. The uniform distribution of the components can be realized
by three-dimensional blending for 3 h. Comparing the macroscopic and microscopic uniformity of the materials
prepared by powders with different particle sizes, the composite systems exhibit the best uniformity when the
average sizes of the aluminum and tungsten powders are 23.2 μm and 10.6 μm. The selection of the powders can
weaken the negative effect of the density difference between the components during the mixing process and meanwhile
avoid the aggregation of tungsten particles with smaller sizes. Based on the mixed powders, composite sheets
are thus prepared with good dispersion of the components, which show a high density of 9.36 g/cm3 and low porosity
below 0.5%. The mechanical strength of the as-prepared materials could reach up to 264 MPa, which is more
than twice of the composite materials prepared by tungsten powders with smaller sizes. The study demonstrates the
important role of the blending method and particle sizes of the raw powders to composition distribution control
within the W-B4C-Al system, which finally determines the performance of the composite materials.
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Received: 31 October 2021
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2022, Vol. 32 
