Thermodynamic analysis of inclusion characteristics in as-cast FeCrAl-(La) alloys

Abstract

ABSTRACTThe characteristics of inclusions in as-cast FeCrAl-(La) alloys were investigated by using scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and confocal laser scanning microscopy (CLSM). The types, morphologies and behaviour of inclusions were examined, and further discussion focused on the analysis of thermodynamic calculations. The results showed that the characteristics of Al2O3 and AlN in FeCrAl alloys were different from those in regular Al-killed steels. The Al–O equilibrium diagram is utilized to understand Al2O3 formation in high-Al steels. The formation of AlN in the liquid phase and at the solidifying front of FeCrAl alloys was investigated based on the theoretical calculations and the in-situ observations at high temperatures. La addition affected the formation of AlN and also generated La-containing inclusions as well. Based on the inclusion observations and the thermodynamic calculations, the predominant formations and possible precipitation path of La–S–O precipitates was theoretically predicted.