Corrosion onset associated with the reinforcement and secondary phases in B4C-6061Al neutron absorber material in H3BO3 solution

• The microstructures in B 4 C-6061Al composites hot-pressed at different temperatures were studied. • The corrosion behavior of the composite in H 3 BO 3 and Cl − -containing H 3 BO 3 solutions were examined. • Quasi in-situ TEM was performed to reveal the pitting initiations. • Corrosion in the composite are mainly associated with B 4 C/Al interface and MgB 2 dispersions. • Dealloying of Mg 2 Si does not obviously deteriorate the corrosion resistance of the composite. The microstructures in B 4 C-6061Al composite hot-pressed at different temperatures (560 °C, 620 °C) are characterized, and the corrosion behavior of the materials is studied using electrochemical tests and quasi in-situ TEM observations. The composite fabricated at 620 °C is composed of more matrix-reinforcement reaction products (Al 3 BC at the interfaces and MgB 2 in the alloy matrix). Corrosion occurred slightly in boric acid but severely in Cl − -containing solution. The B 4 C/Al interface in both samples is preferentially attacked and the MgB 2 dispersions in the high-temperature-pressed composite remarkably promoted the pitting. Dealloying of Mg 2 Si precipitate does not obviously deteriorate the corrosion resistance of the composite.