High temperature oxidation of rare earth permanent magnets. Part 1 – Microstructure evolution and general mechanism

•The microstructure evolution and mechanism of oxidation of (Nd,Pr)FeB magnet at 700–1500 K have been investigated.•Three different oxidation microstructure evolutions were observed at 700–1000 K, 1000–1300 K and 1300–1500 K.•The different microstructures formed during the oxidation have implications for devising strategies for the recycling/recovery process of (Nd,Pr)FeB magnets.