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

The microstructures in B4C-6061Al composite hot-pressed at different temperatures (560 degrees C, 620 degrees 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 degrees C is composed of more matrix-reinforcement reaction products (Al3BC at the interfaces and MgB2 in the alloy matrix). Corrosion occurred slightly in boric acid but severely in Cl--containing solution. The B4C/Al interface in both samples is preferentially attacked and the MgB2 dispersions in the high-temperature-pressed composite remarkably promoted the pitting. Dealloying of Mg2Si precipitate does not obviously deteriorate the corrosion resistance of the composite.