The effects of ausforming strain on bainite transformation in high-carbon low-alloy nanobainite steel were investigated using a Gleeble 3500 thermomechanical simulator machine.The bainite transformation speed at 300&#...The effects of ausforming strain on bainite transformation in high-carbon low-alloy nanobainite steel were investigated using a Gleeble 3500 thermomechanical simulator machine.The bainite transformation speed at 300°C was found to be accelerated by ausforming at 300,600,and 700°C under applied strains ranging from 10% to 50% followed by isothermal transformation at 300°C.The ausformed bainite volume fraction varied with the ausforming strain because of the mechanical stabilization of the deformed austenite.Ausforming at low temperatures not only enhanced the bainite ferrite volume fraction but also refined the microstructure substantially.Although the amount of bainite ferrite might have been reduced with increasing strain,the microstructures were refined by ausforming.展开更多
Low-temperature ausforming(LT-AF)prior to bainitic transformation leads to a noticeable acceleration of bainitic transformation kinetics;however,the effect of LT-AF on the retained austenite(RA)features and the result...Low-temperature ausforming(LT-AF)prior to bainitic transformation leads to a noticeable acceleration of bainitic transformation kinetics;however,the effect of LT-AF on the retained austenite(RA)features and the resulting mechanical properties is still unclear.LT-AF was applied to ultrahigh-strength bainitic steel before austempering.The deformation behavior and the resulting dislocation substructures were investigated by thermomechanical simulator and transmission electron microscopy(TEM).The planar dislocation structures produced during deformation at 350℃ accelerate the bainitic transformation kinetics during isothermal holding.The effect of LT-AF on the bainitic transformation kinetics and the features of RA was elucidated via dilatometer measurement,TEM,scanning electron microscopy,and X-ray diffraction.It is observed that LT-AF not only retains more RA content but also facilitates improved RA stability.This trend is mainly due to the large amounts of planar dislocations in RA and bainitic laths inherited from undercooled austenite caused by LT-AF,the decrease in bainitic sheaves size,and the increase in filmy RA content compared to the sample without ausforming.A large fraction of filmy RA with high stability and the refinement of bainitic sheaves obtained by LT-AF remarkably enhance the strain hardening capacity and achieve significantly better ductility compared to the directly austempered sample.展开更多
基金the National Natural Science Foundation of China(Nos.51271035 and 51371032)for funding this workfinancial support from the National Natural Science Foundation of China(No.51204092)the Key Laboratory Fundamental Research Project of the Education Department of Liaoning Province,China(No.LZ2015046)
文摘The effects of ausforming strain on bainite transformation in high-carbon low-alloy nanobainite steel were investigated using a Gleeble 3500 thermomechanical simulator machine.The bainite transformation speed at 300°C was found to be accelerated by ausforming at 300,600,and 700°C under applied strains ranging from 10% to 50% followed by isothermal transformation at 300°C.The ausformed bainite volume fraction varied with the ausforming strain because of the mechanical stabilization of the deformed austenite.Ausforming at low temperatures not only enhanced the bainite ferrite volume fraction but also refined the microstructure substantially.Although the amount of bainite ferrite might have been reduced with increasing strain,the microstructures were refined by ausforming.
基金The financial support provided by the National Natural Science Foundation of China(No.U1808208)the Fundamental Research Funds for the Central Universities(N2107005)is gratefully acknowledged.
文摘Low-temperature ausforming(LT-AF)prior to bainitic transformation leads to a noticeable acceleration of bainitic transformation kinetics;however,the effect of LT-AF on the retained austenite(RA)features and the resulting mechanical properties is still unclear.LT-AF was applied to ultrahigh-strength bainitic steel before austempering.The deformation behavior and the resulting dislocation substructures were investigated by thermomechanical simulator and transmission electron microscopy(TEM).The planar dislocation structures produced during deformation at 350℃ accelerate the bainitic transformation kinetics during isothermal holding.The effect of LT-AF on the bainitic transformation kinetics and the features of RA was elucidated via dilatometer measurement,TEM,scanning electron microscopy,and X-ray diffraction.It is observed that LT-AF not only retains more RA content but also facilitates improved RA stability.This trend is mainly due to the large amounts of planar dislocations in RA and bainitic laths inherited from undercooled austenite caused by LT-AF,the decrease in bainitic sheaves size,and the increase in filmy RA content compared to the sample without ausforming.A large fraction of filmy RA with high stability and the refinement of bainitic sheaves obtained by LT-AF remarkably enhance the strain hardening capacity and achieve significantly better ductility compared to the directly austempered sample.
