Effect of austenitizing temperature on microstructure and mechanical properties evaluation of microalloyed low-carbon RAFM steel

Abstract

The microstructure and mechanical properties of microalloyed low-carbon reduced activation ferritic/martensitic (RAFM) steel after austenitization at 950 °C, 1000 °C and 1050 °C for 0.5 h and tempering at 750 °C for 1.5 h were investigated using scanning electron microscopy, transmission electron microscopy, electron back scattering diffraction, X-ray diffraction, tensile tests, and impact tests. The grain size and lath width obviously increase because more M23C6 carbides dissolve after austenitization at 1050 °C. Besides, more fine MX particles would precipitate and result in higher dislocation density. Furthermore, the strengthening mechanisms at room temperature were also systematically discussed, the predominant strengthening mechanism changes from grain boundary strengthening and dislocation strengthening to dislocation strengthening when the austenitizing temperature increases from 950 °C to 1000 °C and 1050 °C. After taking the microstructure, strength, ductility, and toughness into thorough consideration, the optimum austenitizing temperature for microalloyed low-carbon RAFM steel is about 1000 °C.