Microstructure evolution and mechanical properties of B4C/6061Al neutron absorber composite sheets fabricated by powder metallurgy

Abstract

B4C particle reinforced 6061Al matrix composites is interestingly used for neutron shielding due to its light weight and good strength and neutron absorbing. In this study, B4C/6061Al neutron absorber composite (B4C/6061Al NAC) sheet containing 30 wt% B4C particle was first fabricated by powder metallurgy (hot pressed sintering→extrusion→rolling), then its microstructure and mechanical properties were investigated. It was found that B4C particles distributed relatively homogeneously in the 6061Al matrix and the composite was mainly consisted of B4C, Al and Al2O3 phases. B4C particles were found to be able to stimulate dynamic recrystallization (DRX) nucleation; restrain the grain growth; and reduce the preferential orientation of the aluminum grains. Moreover, under increasing deformation, amount of DRX was found to increases; the ultimate tensile and yield strength of the composites first increased and then decreased; while its elongation to fracture dropped. The decrease in strength was found to be due to the fracture of large B4C particles and the stress concentration in the locations between the B4C particle and the 6061Al matrix.