Precipitation evolution during the annealing of an interstitial-free steel

Thermoelectric power was used to investigate the evolution of precipitation in a hot-rolled Ti added interstitial-free (IF) steel sheet, during different annealing treatments. Transmission electron microscopy was carried out on thin foils and carbon extraction replicas in order to test the sensitivity of the thermoelectric power technique. Internal friction measurements were also performed. The microstructural evolution of the material during different heat treatments was followed and the presence of carbon in solid solution in the material, even after long annealing times at high temperatures, was noted. According to the literature, in IF steel, all the carbon should be precipitated after such heat treatments. Finally, the existence of carbides of ε-type in the hot rolled state was shown. It is concluded that the extensive use of thermoelectric power measurements in combination with more common techniques is promising in metallurgical work.