Hot-rolled TRIP steel with 0. 038% Nb was thermomechanically processed on a Gleeble simulation test machine. The microstructural evolution and the precipitation behavior of Nb were analyzed by optical microscopy,scanning electron microscopy,and transmission electron microscopy. The amount of Nb in solution / precipitation was quantitatively measured by inductively coupled plasma optical emission spectrometry( ICP-OES). After austenization at 1250 ℃ for 5 min,about 70% of added Nb is dissolved into austenite...