In situ TOF neutron diffraction during phase transformation in an engineering steel

Phase transformations on heating and cooling or during thermo-mechanically controlled processing (TMCP) for a low alloyed steel were studied by means of in situ neutron diffraction. Cylindrical specimens were quenched after austenitization and hence the starting microstructure was martensite (bct). Tempering behavior accompanying cementite precipitation and ferrite (bcc) to austenite (fcc) reverse transformation were observed upon heating. During cooling, austenite to ferrite and pearlite transformations were observed in diffraction profiles, where nearly equilibrium microstructural changes were confirmed. In TMCP simulation measurements, plastic deformation of austentite at an elevated temperature was found to accelerate the ferrite transformation.