Neutron-irradiation effects on a metal-matrix composite

The study examined the effects of nuclear irradiation on the mechanical properties of a metal matrix composite to update composite theory to include nuclear effects and to determine the feasibility of nuclear applications of metal matrix composites. An NS 355 stainless steel fiber/2024-T6 aluminum matrix composite was cut into specimens which were then divided into four sample groups. Three of these groups were irradiated to fast neutron dosages of 1.56, 2.84, and 4.68 × 1018 n/cm2. Microhardness and flexure tests were performed on each of the four sample groups. Fracture surfaces of all sample groups were viewed by scanning electron microscopy. Strength increases and ductility decreases with increasing dosages are generally observed in the aluminum matrix and the stainless steel fibers. The high degree of matrix hardening and subsequent saturation with increasing dosage, leading to changes in the relative failure strain of matrix and fiber, is identified as the controlling mechanism of the composite strength changes in flexure. Existing composite theory is concluded to be applicable to nuclear irradiated composites without modification. Nuclear applications are most feasible in fast reactors, where the tailorability of a metal matrix composite might provide the technical breakthrough needed to combat the severe materials problems inherent to fast reactors.