Microstructure and Mechanical Properties of B₄C-Al

Neutron absorbing material (B₄C-Al) was concerned as low density and high boron content, which was applied to shielding structure design in US nuclear power ships, storage lattice in spent fuel pools and shipping containers. Key laboratory of reactor fuel and materials in nuclear power institute of China (NPIC) developed neutron absorbing plate of B₄C-Al, in which B₄C particles was uniformly dispersed. The enhanced phase of the plate was bonding to the substrate and there was no obvious interface product. At room temperature, the plate's tensile strength was up to 250 MPa. However, with the increasing of temperature, the yield and tensile strength of the plate decreased, but the elongation increased after fracture. By observing the fracture surface, amounts of small dimples were found in the substrate, and lots of cracks parallel to the rolling direction were in the fracture surface. Secondary cracks produced from the junction of some big B₄C particles with the substrate, and cracks appeared in portion of B₄C particles. The fracture of material was caused by two reasons. The first one was the plastic failure due to nucleation, growth and aggregation in the substrate pores, and the other one was debonding fracture between the enhanced phase to the substrate. (authors)