AP-FIM analysis of ultrafine carbonitrides in fire-resistant steel for building construction

The atom-probe field-ion microscope (AP-FIM) can be used to observe materials at an atomic level and analyze their individual atoms. This report presents an application in which the AP-FIM was used to clarify the role of the combined addition of niobium and molybdenum in improving the high-temperature strength of fire-resistant steel for building construction. Findings obtained about the composition of ultrafine carbonitrides, which could not be analyzed by conventional electron microscopy, and about the elemental distribution of the carbonitride/ferrite matrix interface are briefly introduced.