Dual Role of Boron in the Elevated Temperature Embrittlement of Irradiated Complex Heat-resistant Alloys

Abstract

IN a recent communication, Roberts and Harries¹ discuss some investigations which were made on elevated temperature embrittlement induced in 20 per cent chromium : 25 per cent nickel : niobium-stabilized austenitic steel by irradiation with thermal neutrons. Similar observations^2,3 were noted by us in the case of precipitation hardening and also solution strengthened alloys, which were either irradiated at pile ambient or at elevated temperatures and afterwards post-irradiation tested at elevated temperatures in conventional creeprupture testing equipment. The high-temperature brittleness was further observed⁴ for irradiation conditions in which the fast neutron and thermal neutron dosages were as low as 8 × 10¹⁴ nvt and 4 × 10¹⁵ nvt, respectively. This thermal neutron dose, for example, is about a factor of 1.9 × 10³ lower than those reported by Roberts and Harries.