Precipitation and Recrystallization Behaviors of a High-Nitrogen Austenitic Stainless Steel Aging at 90°C

The behaviors of precipitation and recrystallization aging at 900 after cold work in a Fe-18Cr-12Mn-0.48N high-nitrogen austenitic stainless steel were investigated by means of optical microscopy (OM) and transmission electron microscopy (TEM). The results show that precipitation and recrystallization occur simultaneously after aging at 900 for 10min. The precipitates firstly appear at dislocation, sub-boundary and inside the subgrain. Precipitation at these positions hinders the formation of recrystallization nucleus. With aging time increasing, precipitates appear in the recrystallized grain boundary and inside the grain. Precipitation at these positions hinders the growth of the recrystalized grains.

MICROSTRUCTURE IN WORN SURFACE OF HADFIELD STEEL CROSSING

In this paper a failed Hadfield (high manganese austenite) steel crossing used in railway system was studied. The microstructure in the worn surfaces of the crossing was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy and Mössbauer spectroscopy. The results indicated that a nanocrystallization layer formed on the surface of the crossing served. The formation mechanism of the nanocrystalline is the discontinuous dynamic recrystallization. The energy for the recrystallization nucleus formation originates from the interactions between the twins, the dislocations, as well as twin and dislocation. High-density vacancies promoted the recrystallization process including the dislocation climb and the atom diffusion.