Austenitic stainless steels(ASSs)are widely used in various in-dustries such as aerospace,nuclear energy,food,and biotechnol-ogy owing to their exceptional combination of corrosion resistance,weldability,toughness,and...Austenitic stainless steels(ASSs)are widely used in various in-dustries such as aerospace,nuclear energy,food,and biotechnol-ogy owing to their exceptional combination of corrosion resistance,weldability,toughness,and formability[1,2].However,a signifi-cant drawback of ASSs is their low yield strength,which limits their applications in extreme environments[3].Grain boundary(GB)engineering plays a crucial role in enhancing the strength of ASSs[4,5].For instance,grain refinement techniques such as cold rolling followed by annealing[6],severe plastic deformation(SPD)[7],and surface mechanical attrition/rolling treatments[8,9]introduce high-angle GBs(HAGBs)into ASSs,thereby improving their strength.However,the high density of HAGBs limits their ca-pacity for dislocation storage and multiplication,leading to a sig-nificant loss of ductility[10,11].Additionally,several studies have shown that twin boundaries(TBs)can simultaneously enhance the strength,toughness,and corrosion resistance of ASSs[12,13].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
EBSD characterization of density and dispersion of high angle boundaries was carried out in niobium microalloyed steels of HTP base chemistry with 0.09 wt % Nb,which were thermo-mechanically processed under laboratory...EBSD characterization of density and dispersion of high angle boundaries was carried out in niobium microalloyed steels of HTP base chemistry with 0.09 wt % Nb,which were thermo-mechanically processed under laboratory conditions.Similar studies were carried out in higher grade (X-100 and above) line pipe steels with different chemistries,which were processed under simulation of industrial rolling conditions.The twin objectives are (i) to understand the effect of chemistry and processing parameters on the density and dispersion of high angle boundaries,and (ii) to correlate the microstructure and density of high angle boundaries with strength and fracture properties.The present studies confirm that refinement of austenite grain size prior to pancaking,large strain accumulation in austenite conditioning,alloy design with high hardenability and high cooling rates are essential to control high density and uniformity of dispersion of high angle boundaries in the final microstructure in order to achieve high strength,toughness,low DBTT and consistently 100% ductile shear in DWTT in thermo-mechanically rolled higher grade line pipe steels.展开更多
Based on the parent austenite orientation reconstruction method,it is aimed to reveal the origination of high angle grain boundaries(HAGBs)and its relationship with ductility of H13 steel.The orientation relationship ...Based on the parent austenite orientation reconstruction method,it is aimed to reveal the origination of high angle grain boundaries(HAGBs)and its relationship with ductility of H13 steel.The orientation relationship between martensite and parent austenite of quenched H13 samples was(123.5°,9.3°,192.5°),which agreed with the Kurdumov–Sachs relationship.The variant distribution of quenched samples was dominated by close-packed plane group,and its high length fraction of V1/V2 inter-variant boundaries of calculated 62.6%was mainly contributed to HAGBs(>45°).When the quenched H13 samples underwent the pre-tempering treatment,their density of HAGBs(>45°)notably increased from 1.33 to 2.39μm^(−1),which improved its total elongation from 8.3%to 11.5%.Compared with the quenched H13 samples,the length fraction of V1/V2 inter-variant boundaries of H13 samples with pre-tempering for 5,10 and 60 min was reduced by 6.7%,7.0%and 7.5%,respectively.During pre-tempering treatment,V1/V3&V5 variant pairs,etc.,merged V1/V2 variant pair by strain-induced grain boundary migration,which decreased the length fraction of V1/V2 inter-variant boundaries by 7.0%.The pre-tempering treatment significantly increased HAGBs(>45°)of H13 samples by sub-grains coarsening and strain-induced grain boundary migration mechanism.展开更多
基金financially supported by the National Key R&D program(No.2022YFB3707501)the GDAS’Project of Science and Technology(No.2022GDASZH-2022010202)the Guangdong Provincial Project(Nos.2022A0505050053,2021B1515120071,and 2020B1515130007)。
文摘Austenitic stainless steels(ASSs)are widely used in various in-dustries such as aerospace,nuclear energy,food,and biotechnol-ogy owing to their exceptional combination of corrosion resistance,weldability,toughness,and formability[1,2].However,a signifi-cant drawback of ASSs is their low yield strength,which limits their applications in extreme environments[3].Grain boundary(GB)engineering plays a crucial role in enhancing the strength of ASSs[4,5].For instance,grain refinement techniques such as cold rolling followed by annealing[6],severe plastic deformation(SPD)[7],and surface mechanical attrition/rolling treatments[8,9]introduce high-angle GBs(HAGBs)into ASSs,thereby improving their strength.However,the high density of HAGBs limits their ca-pacity for dislocation storage and multiplication,leading to a sig-nificant loss of ductility[10,11].Additionally,several studies have shown that twin boundaries(TBs)can simultaneously enhance the strength,toughness,and corrosion resistance of ASSs[12,13].
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.
基金CBMM,BrazilChinese Government scholarship+1 种基金Evraz Inc NA,ReginaNSERC,Canada
文摘EBSD characterization of density and dispersion of high angle boundaries was carried out in niobium microalloyed steels of HTP base chemistry with 0.09 wt % Nb,which were thermo-mechanically processed under laboratory conditions.Similar studies were carried out in higher grade (X-100 and above) line pipe steels with different chemistries,which were processed under simulation of industrial rolling conditions.The twin objectives are (i) to understand the effect of chemistry and processing parameters on the density and dispersion of high angle boundaries,and (ii) to correlate the microstructure and density of high angle boundaries with strength and fracture properties.The present studies confirm that refinement of austenite grain size prior to pancaking,large strain accumulation in austenite conditioning,alloy design with high hardenability and high cooling rates are essential to control high density and uniformity of dispersion of high angle boundaries in the final microstructure in order to achieve high strength,toughness,low DBTT and consistently 100% ductile shear in DWTT in thermo-mechanically rolled higher grade line pipe steels.
基金The research is financially supported by the National Key Research and Development Program of China(Nos.2016YFB0300900 and 2017YFB0306202).
文摘Based on the parent austenite orientation reconstruction method,it is aimed to reveal the origination of high angle grain boundaries(HAGBs)and its relationship with ductility of H13 steel.The orientation relationship between martensite and parent austenite of quenched H13 samples was(123.5°,9.3°,192.5°),which agreed with the Kurdumov–Sachs relationship.The variant distribution of quenched samples was dominated by close-packed plane group,and its high length fraction of V1/V2 inter-variant boundaries of calculated 62.6%was mainly contributed to HAGBs(>45°).When the quenched H13 samples underwent the pre-tempering treatment,their density of HAGBs(>45°)notably increased from 1.33 to 2.39μm^(−1),which improved its total elongation from 8.3%to 11.5%.Compared with the quenched H13 samples,the length fraction of V1/V2 inter-variant boundaries of H13 samples with pre-tempering for 5,10 and 60 min was reduced by 6.7%,7.0%and 7.5%,respectively.During pre-tempering treatment,V1/V3&V5 variant pairs,etc.,merged V1/V2 variant pair by strain-induced grain boundary migration,which decreased the length fraction of V1/V2 inter-variant boundaries by 7.0%.The pre-tempering treatment significantly increased HAGBs(>45°)of H13 samples by sub-grains coarsening and strain-induced grain boundary migration mechanism.
