“…The microstructure of second phases in Zr alloys has a profound influence on their corrosion behaviour [6,13,33], and a considerable body of research has studied the microstructural changes in Zr-2.5Nb alloys during heat-treatment, thermal decomposition or irradiation, especially in the temperature range from 400°C to 600°C for relatively short times (up to hundreds of hours) [13][14][15]34,35]. The decomposition behaviour of β-Zr at in-service temperatures over much longer time (more closely corresponding to the real in-service situation) has been less reported.…”