In this research, we tried to find a simple processing method to break up the network carbides in ultrahigh carbon steels (UHCS). Our results revealed that Al addition was favorable to the decrease in the proeutectoid...In this research, we tried to find a simple processing method to break up the network carbides in ultrahigh carbon steels (UHCS). Our results revealed that Al addition was favorable to the decrease in the proeutectoid carbides, the pearlite-colony size and the pearlitic interlamellar spacing of the forged microstructures, and that a fully-pearlitic structure was obtained in the UHCS containing 1.6 wt pct Al. The quenching-and-tempering process resulted in fine microstructure in those steels. On the other hand, the strength of the UHCSs increased with the increase of the Al content, and the highest strength was obtained at the UHCS with 1.6 wt pct Al. The UHCSs with Al contents higher than 1.3 wt pct showed a high tensile strength of more than δb=1000 MPa and good ductility of higher than δ5=10% at ambient temperature.展开更多
Microstructure and mechanical properties of modified ultrahigh carbon(1.6%C)steels with different Mo additions(0,0.3%,0.5%,and 0.8%,mass fraction)were studied in their as-cast and quenched then tempered conditions by ...Microstructure and mechanical properties of modified ultrahigh carbon(1.6%C)steels with different Mo additions(0,0.3%,0.5%,and 0.8%,mass fraction)were studied in their as-cast and quenched then tempered conditions by optical microscopy,scanning electronic microscopy,X-ray diffraction and hardness and toughness tests,respectively.The results show that the continuous eutectic carbide network structure has been broken down and changed to partial isolated and finer particles embedded in matrix of as-cast alloy by modification.Carbides in both quenched and tempered specimens have been refined effectively after the addition of Mo.Specimen containing 0.5% Mo shows the finest microstructures with carbides dispersed homogeneously in martensite matrix and demonstrates highest impact toughness of 18.4 J/cm2 and hardness of 50 HRC.展开更多
Various isothermal compression tests are carried out on an ultrahigh carbon steel （1.2% C in mass percent）, initially quenched or spheroidized, using a Gleeble-3500 system. The true stress is observed to decrease wi...Various isothermal compression tests are carried out on an ultrahigh carbon steel （1.2% C in mass percent）, initially quenched or spheroidized, using a Gleeble-3500 system. The true stress is observed to decrease with increas ing temperature and decreasing strain rate. The true stress of the initially quenched steel is lower than that of the ini- tially spheroidized steel at high deformation temperature （700 ~C） and low deformation strain rate （0. 001 s-1 ）. The value of the deformation activation energy （Q） of the initially quenched steel （331.56 kJ/mol） is higher than that of the initially spheroidized steel （297.94 kJ/mol）. The initially quenched steel has lower efficiency of power dissipation and better processability than the initially spheroidized steel. The warm compression promotes the fragmentation and the spheroidization of lamellar cementites in the initially quenched steel. The fragmentation of lamellar cementites is the spheroidizing mechanism of the eementites in the initially quenched steel. Results of transmission electron microscope investigation showed that fine grains with high angle boundaries are obtained by deformation of the initially quenched steel.展开更多
基金This work was performed under the auspices of the Natural Science Foundation of Hebei Province under grant No.500023.
文摘In this research, we tried to find a simple processing method to break up the network carbides in ultrahigh carbon steels (UHCS). Our results revealed that Al addition was favorable to the decrease in the proeutectoid carbides, the pearlite-colony size and the pearlitic interlamellar spacing of the forged microstructures, and that a fully-pearlitic structure was obtained in the UHCS containing 1.6 wt pct Al. The quenching-and-tempering process resulted in fine microstructure in those steels. On the other hand, the strength of the UHCSs increased with the increase of the Al content, and the highest strength was obtained at the UHCS with 1.6 wt pct Al. The UHCSs with Al contents higher than 1.3 wt pct showed a high tensile strength of more than δb=1000 MPa and good ductility of higher than δ5=10% at ambient temperature.
基金the Chang Gao Advanced Materials Co.,Ltd.for the financial support
文摘Microstructure and mechanical properties of modified ultrahigh carbon(1.6%C)steels with different Mo additions(0,0.3%,0.5%,and 0.8%,mass fraction)were studied in their as-cast and quenched then tempered conditions by optical microscopy,scanning electronic microscopy,X-ray diffraction and hardness and toughness tests,respectively.The results show that the continuous eutectic carbide network structure has been broken down and changed to partial isolated and finer particles embedded in matrix of as-cast alloy by modification.Carbides in both quenched and tempered specimens have been refined effectively after the addition of Mo.Specimen containing 0.5% Mo shows the finest microstructures with carbides dispersed homogeneously in martensite matrix and demonstrates highest impact toughness of 18.4 J/cm2 and hardness of 50 HRC.
基金Item Sponsored by National Natural Science Foundation of China(50271060)Program for Changjiang Scholars and Innovative Research Team in University of China(IRT0650)Natural Science Foundation of Hebei Province of China(503291)
文摘Various isothermal compression tests are carried out on an ultrahigh carbon steel （1.2% C in mass percent）, initially quenched or spheroidized, using a Gleeble-3500 system. The true stress is observed to decrease with increas ing temperature and decreasing strain rate. The true stress of the initially quenched steel is lower than that of the ini- tially spheroidized steel at high deformation temperature （700 ~C） and low deformation strain rate （0. 001 s-1 ）. The value of the deformation activation energy （Q） of the initially quenched steel （331.56 kJ/mol） is higher than that of the initially spheroidized steel （297.94 kJ/mol）. The initially quenched steel has lower efficiency of power dissipation and better processability than the initially spheroidized steel. The warm compression promotes the fragmentation and the spheroidization of lamellar cementites in the initially quenched steel. The fragmentation of lamellar cementites is the spheroidizing mechanism of the eementites in the initially quenched steel. Results of transmission electron microscope investigation showed that fine grains with high angle boundaries are obtained by deformation of the initially quenched steel.
