TEM observation of carbide precipitates in bainite has been carried out for steel 40CMD8. Specimens transformed at 350 ℃ and 450 ℃ without external stress contain respectively the lower and the upper bainite. No fun...TEM observation of carbide precipitates in bainite has been carried out for steel 40CMD8. Specimens transformed at 350 ℃ and 450 ℃ without external stress contain respectively the lower and the upper bainite. No fundamental change in carbide precipitation is observed in specimen transformed at 350 ℃ under stress of 128 MPa. The very fine cementite is found precipitated within the upper bainite plates in specimen transformed at 450 ℃ under stress of 144 MPa, which can be explained as the result of the difficulty of carbon diffusing out of the massive ferrite plate within a much shortened transformation time due to the external stress. For all the specimens examined, Bagaryatskii orientation relationship is found existing between the carbides and ferrite matrix.展开更多
The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the ...The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the conventionai types of mierostructure. The influence of the isothermal transformation temperatures on the mierostrueture and the mechanical properties of the steel bas been examined. Therefore, the strengthening meehanism of the new dual phase steel with ultra-high strength has been revealed.展开更多
TEM observation and analysis have been conducted on bainitie transformation with and without the influence of externally applied tensile sress for alloyed steel 35MV7. Recrystallizafion was found to occur within the b...TEM observation and analysis have been conducted on bainitie transformation with and without the influence of externally applied tensile sress for alloyed steel 35MV7. Recrystallizafion was found to occur within the bainitic structures transformed at 450 ℃ in cases of both with and without the application of external stress, and coupling between the reconstructive and displacive mechanisms is expected, due to the relatively high holding temperature and high dislocation density yielded with the displacive mechanism. RecrystaUization was not observed within the bainitic structures transformed at lower temperature of 350 ℃, both with and without the application of stress; However, for the stressed specimen, the structure with very fine subgrains was found to be preserved and not reconstructed thermically, due to the low temperature and short holding time.展开更多
文摘TEM observation of carbide precipitates in bainite has been carried out for steel 40CMD8. Specimens transformed at 350 ℃ and 450 ℃ without external stress contain respectively the lower and the upper bainite. No fundamental change in carbide precipitation is observed in specimen transformed at 350 ℃ under stress of 128 MPa. The very fine cementite is found precipitated within the upper bainite plates in specimen transformed at 450 ℃ under stress of 144 MPa, which can be explained as the result of the difficulty of carbon diffusing out of the massive ferrite plate within a much shortened transformation time due to the external stress. For all the specimens examined, Bagaryatskii orientation relationship is found existing between the carbides and ferrite matrix.
文摘The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the conventionai types of mierostructure. The influence of the isothermal transformation temperatures on the mierostrueture and the mechanical properties of the steel bas been examined. Therefore, the strengthening meehanism of the new dual phase steel with ultra-high strength has been revealed.
文摘TEM observation and analysis have been conducted on bainitie transformation with and without the influence of externally applied tensile sress for alloyed steel 35MV7. Recrystallizafion was found to occur within the bainitic structures transformed at 450 ℃ in cases of both with and without the application of external stress, and coupling between the reconstructive and displacive mechanisms is expected, due to the relatively high holding temperature and high dislocation density yielded with the displacive mechanism. RecrystaUization was not observed within the bainitic structures transformed at lower temperature of 350 ℃, both with and without the application of stress; However, for the stressed specimen, the structure with very fine subgrains was found to be preserved and not reconstructed thermically, due to the low temperature and short holding time.
