The effects of sulfate reduced bacterium （SRB） on the corrosion behavior of 10CrMoAl steel in seawater were studied by chemical immersion, potentiodynamic polarization, electrochemical impedance spectroscopy measure...The effects of sulfate reduced bacterium （SRB） on the corrosion behavior of 10CrMoAl steel in seawater were studied by chemical immersion, potentiodynamic polarization, electrochemical impedance spectroscopy measurement, and scanning electron microscope techniques. The results show that the content of element sulfur in the corrosion product of 10CrMoAl steel in seawater with SRB is up to 9. 23 %, which is higher than that of the same in sterile seawater. X-ray diffraction demonstrates that the main corrosion product is FeS. SRB increases the corrosion rate by anodic depolarization of the metabolized sulfide product. SEM observation indicates that the corrosion product is not distributed continuously; in addition, bacilliform sulfate-reduced bacterium accumulates on the local surface of 10CrMoAl steel. Hence, SRB enhances sensitivity to the localized corrosion of 10CrMoAl steel in seawater.展开更多
The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as fo...The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as follaws. In the coarse-grained austenitized region（ Tm = 1 300℃ ＋ 1300℃ ） ,the microstructure is in good toughness. At the condition of Tm = 1 300℃ ＋ 850℃ and t8/5=43 s, the toughness decreases heavily because M-A constituent and twin martensite appear at the prior aastenite grain boundaries. When Tm= 1300℃ ＋ 850℃ or 1300℃ ＋ 730℃ and t8/5 = 85 s, local brittle zone is formed because of relatively coarse granular bainite.展开更多
Thermo-mechanical experiments on martensitic heat-resistant 40Cr10Si2Mo steel were conducted using a Gleeble simulator in temperature and strain rate ranges of 1073–1373 K and 0.1–20 s^(-1),respectively.Processing m...Thermo-mechanical experiments on martensitic heat-resistant 40Cr10Si2Mo steel were conducted using a Gleeble simulator in temperature and strain rate ranges of 1073–1373 K and 0.1–20 s^(-1),respectively.Processing maps were developed and correlated with deformed microstructures based on the dynamic material model theory.The analysis of the maps revealed that both applied temperature and strain rate had significant effects on the power dissipation efficiency and flow instability of the steel alloy.Electron backscatter diffraction analysis was also implemented to study the effect of deformation conditions on martensitic morphology.The results showed that higher temperatures and strain rates led to a fine martensitic packet,and the martensite lath increased in width at high temperatures.Two deformation domains,which exhibit different recrystallization processes,were recognized.The discontinuous dynamic recrystallization(DRX)mechanism in the low strain rate domain was characterized by the migration and growth of high-angle grains during straining.In contrast,in the high strain rate domain,the development of new grain boundaries is primarily associated with the deformation microbands in the low-temperature deformation domain.As the temperature increased,the high dislocation density accelerated the migration of the grain boundaries.Furthermore,the DRX mechanism changed from continuous DRX to post-DRX.This change in the DRX mechanism type was attributed to the time during which the sample remained high temperature after deformation.展开更多
The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and ene...The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.展开更多
In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing Fe-10Ni-7Mn steels were characterized. The results of X-ray analysis as well as scanning electron microscopy co...In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing Fe-10Ni-7Mn steels were characterized. The results of X-ray analysis as well as scanning electron microscopy coupled with energy dispersive X-ray spectroscopy indicated the formation of （Fe, Ni, Mn）17Y2 precipitates with hexagonal structure in a Fe-10Ni-7Mn-0.8Y （wt.%） alloy. Lattice parameters of these precipitates were calculated as follows：a=0.8485 nm and c=0.8274 nm. Formation of Y2O3 sub-micron particles was also confirmed in both yttrium bearing steels via electrolytic phase extraction method. The effect of these precipitates on the prior austenite grain size was investigated. The results revealed that these precipitates had an effective role in controlling the prior austenite grain size.展开更多
文摘The effects of sulfate reduced bacterium （SRB） on the corrosion behavior of 10CrMoAl steel in seawater were studied by chemical immersion, potentiodynamic polarization, electrochemical impedance spectroscopy measurement, and scanning electron microscope techniques. The results show that the content of element sulfur in the corrosion product of 10CrMoAl steel in seawater with SRB is up to 9. 23 %, which is higher than that of the same in sterile seawater. X-ray diffraction demonstrates that the main corrosion product is FeS. SRB increases the corrosion rate by anodic depolarization of the metabolized sulfide product. SEM observation indicates that the corrosion product is not distributed continuously; in addition, bacilliform sulfate-reduced bacterium accumulates on the local surface of 10CrMoAl steel. Hence, SRB enhances sensitivity to the localized corrosion of 10CrMoAl steel in seawater.
文摘The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as follaws. In the coarse-grained austenitized region（ Tm = 1 300℃ ＋ 1300℃ ） ,the microstructure is in good toughness. At the condition of Tm = 1 300℃ ＋ 850℃ and t8/5=43 s, the toughness decreases heavily because M-A constituent and twin martensite appear at the prior aastenite grain boundaries. When Tm= 1300℃ ＋ 850℃ or 1300℃ ＋ 730℃ and t8/5 = 85 s, local brittle zone is formed because of relatively coarse granular bainite.
基金received from Science and Technology Program of Xi'an(2020KJRC0051)The research leading to these results received funding from the National Natural Science Foundation of China under Grant Agreement No.52174371.
文摘Thermo-mechanical experiments on martensitic heat-resistant 40Cr10Si2Mo steel were conducted using a Gleeble simulator in temperature and strain rate ranges of 1073–1373 K and 0.1–20 s^(-1),respectively.Processing maps were developed and correlated with deformed microstructures based on the dynamic material model theory.The analysis of the maps revealed that both applied temperature and strain rate had significant effects on the power dissipation efficiency and flow instability of the steel alloy.Electron backscatter diffraction analysis was also implemented to study the effect of deformation conditions on martensitic morphology.The results showed that higher temperatures and strain rates led to a fine martensitic packet,and the martensite lath increased in width at high temperatures.Two deformation domains,which exhibit different recrystallization processes,were recognized.The discontinuous dynamic recrystallization(DRX)mechanism in the low strain rate domain was characterized by the migration and growth of high-angle grains during straining.In contrast,in the high strain rate domain,the development of new grain boundaries is primarily associated with the deformation microbands in the low-temperature deformation domain.As the temperature increased,the high dislocation density accelerated the migration of the grain boundaries.Furthermore,the DRX mechanism changed from continuous DRX to post-DRX.This change in the DRX mechanism type was attributed to the time during which the sample remained high temperature after deformation.
基金Project supported by Shandong Natural Science Foundation (ZR2010EQ017)
文摘The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.
文摘In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing Fe-10Ni-7Mn steels were characterized. The results of X-ray analysis as well as scanning electron microscopy coupled with energy dispersive X-ray spectroscopy indicated the formation of （Fe, Ni, Mn）17Y2 precipitates with hexagonal structure in a Fe-10Ni-7Mn-0.8Y （wt.%） alloy. Lattice parameters of these precipitates were calculated as follows：a=0.8485 nm and c=0.8274 nm. Formation of Y2O3 sub-micron particles was also confirmed in both yttrium bearing steels via electrolytic phase extraction method. The effect of these precipitates on the prior austenite grain size was investigated. The results revealed that these precipitates had an effective role in controlling the prior austenite grain size.
