Dynamic Recrystallization and Dynamic Precipitation Behaviors of a 17Ni–0.2C Martensite Steel Studied by In Situ Neutron Diffraction

The austenite precipitation and dynamic recrystallization behaviors of 17Ni–0.2C martensite steel during isothermal tempering at 500°C followed by isothermal warm compression at 8.3×10−4/s were investigated in situ using neutron diffraction. The Rietveld analysis of Time-Of-Flight neutron diffraction profiles revealed that the austenite amount increased by about 1.5% during 10 min isothermal holding while the warm compression at 500°C accelerated the austenite precipitation. Splitting of the austenite (111) peak occurred and then disappeared during warm compression. Based on integrated intensities obtained by single peak fitting of neutron spectra, it was found from the axial neutron spectra that the ferrite (110) peak intensity rapidly decreased and the ferrite (200) and (211) peak intensities slowly increased during warm compression; the occurrence of dynamic recrystallization led to an evident deviation from this trend. The comparison between lattice strains and texture indexes of austenite and ferrite suggested that the austenite was harder than the ferrite at 500°C. Thus, heterogeneous deformation occurred in the ferrite, leading to accelerated dynamic recrystallization.