Precipitate Morphology and Chemistry in Reheated and As-cast Nb-Ti Microalloyed Austenite (original) (raw)

The morphology and chemical compositions of Ti-rich cube and lath precipitates, and of Nb-rich and MnS particles precipitated on them, were investigated in NbTi-microalloyed, low carbon steel. In previously controlled rolled steel, laths were richer in Ti than cubes and both were richer in Ti than predicted by a model of the solution thermodynamics. As-cast steel contained only Nb-rich particles, including cubes, which dissolved, as Ti-rich cubes and laths nucleated, during reheating. MnS and Nb rich carbonitrides precipitated on Ti-rich particles in a variety of morphologies during cooling from reheating temperatures. The premature loss of microalloy precipitants from solution is expected to affect subsequent microstructure development.