PNNL

Abstract

A thermal neutron-absorbing metal matrix composite (MMC) material comprised of Al3Hf intermetallic particles in an aluminum matrix has been developed to create a fast flux irradiation testing environment in mixed spectrum reactors. Materials were fabricated via hot pressing of high purity aluminum powders to contain micrometer-size Al3Hf at volume fractions of 20.0, 28.4, and 36.5%. Microindentation hardness and tensile tests were performed on unirradiated specimens and on specimens irradiated at 339 to 348K (66 to 75°C) to four dose levels ranging from approximately 1 to 4 dpa. Room temperature tensile and hardness testing of unirradiated specimens revealed a linear relationship between volume fraction and strength, while the tensile data showed a strong decrease in elongation between 20 and 36.5% volume fraction. Tensile tests conducted at 473K (200°C) on unirradiated material showed the same trends. Tensile tests on irradiated specimens were conducted only at 473K due to having a limited number of specimens, and these observations showed the typical increase in strength and decrease in ductility with dose that is common for metallic materials irradiated at =0.4Tm. Room temperature hardness tests on irradiated materials also showed the same trend as the tensile strength. The difference in strength between the three different volume fraction materials was roughly maintained with dose suggesting that irradiation-induced hardening was additive to the strengthening produced by the Al3Hf particles.