Effect of Al on Microstructure and Corrosion Behavior of Low Neutron Absorption Cross-Section Ti-Zr-Nb High Entropy Alloys

The effect of Al on the microstructure and corrosion behavior of low neutron absorption cross-section Ti-Zr-Nb high entropy alloys was investigated. The phase diagram, microstructure, oxidation behavior and corrosion behavior of Ti-Zr-Nb alloys without Al addition and with similar to 15at% Al were compared. The phase diagram shows that below the melting temperature, Ti-Zr-Nb ternary alloys are bcc phase, and Al is inclined to form intermetallics in Ti-Zr-Nb alloys, and thus reduces the single-phase bcc temperature region in phase diagram. XRD and TEM results show that as-cast Ti-Zr-Nb ternary alloys is simple bcc structure, and Al will transform the crystal structure to ordered B2 structure. The corrosion behavior of Ti-Zr-Nb alloys was studied by thermogravimetric analysis and autoclave exposure. Results show that corrosion oxide layer formed on TiZrNb ternary alloys tends to spall during corrosion process, while Al addition will increase the stability of oxide layer without changing the main type of oxide formed during corrosion process. Oxidation kinetics was evaluated by calculating reaction rate constants and activation energies, and it is found that the high temperature oxidation property of Ti-Zr-Nb alloys with Al addition is comparable to that of Zr alloys.