Corrosion is an essential issue limiting the application of high-strength low-carbon steel in seawater environment. The impact of retained austenite on its corrosion behavior with immersion experiments and related cor...Corrosion is an essential issue limiting the application of high-strength low-carbon steel in seawater environment. The impact of retained austenite on its corrosion behavior with immersion experiments and related corrosion sensor technology was explored. A model that clarifies the micro-galvanic effect and the heat-induced changes to the shape and composition of retained austenite was used to discuss the findings. The results indicated that retained austenite was generated following an intercritical process and demonstrated approximately 48 mV higher Volta potential than the matrix. The retained austenite content first increased and then decreased with increasing intercritical temperatures, while reaching the maximum value of 8.5% at 660℃. With the increase in retained austenite content, the corrosion rate was increased by up to 32.8% compared to “quenching + tempering” (QT) specimen. The interfaces between the retained austenite and matrix were the priority nucleation sites for corrosion. Moreover, the retained austenite reduced the corrosion resistance of the steel by increasing the micro-galvanic effect and reducing rust layer compactness.展开更多
Hydrogen-induced cracking (HIC) is one of the most complex material problems that hydrogen can diffuse into and interact with microstructure, degrading their mechanical properties. Microstructural modification is an e...Hydrogen-induced cracking (HIC) is one of the most complex material problems that hydrogen can diffuse into and interact with microstructure, degrading their mechanical properties. Microstructural modification is an effective way to enhance the resistance to HIC. The present study focused on the relationship between the retained austenite (RA) and HIC behavior in NiCrMoV/Nb multi-alloying ultra-strength steel. Results demonstrated that the maximum volume fraction of RA of 9.31% was obtained for QL30T specimen. After the deep cryogenic pretreatment, the volume fraction of RA reduced to 8.8%. RA could reduce the effective diffusion coefficient, while deep cryogenic pretreatment increased the susceptibility of the steel to HIC by a maxim of 14.8%. This was mainly due to the transformation of retained austenite into martensite, degrading the mechanical properties under hydrogen-charged condition. In addition, the deep cryogenic pretreatment had a significant effect on the crack initiation and propagation, with the intergranular (IG) fracture becoming the dominant fracture mode where an increase in the number of secondary cracks in the section. The interfaces of RA and matrix, as well as the grain boundaries, were the preferred sites for cracks initiation.展开更多
To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay...To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay Basin.This analysis involves Rock-Eval pyrolysis,pyrolysis simulation experiments,Gas Chromatograph Mass Spectrometer(GC-MS),and reactive molecular dynamics simulations(ReaxFF).The results revealed the retained oil primarily consisted of n-alkanes with carbon numbers ranging from C14 to C36.The generation of retained oil occurred through three stages.A slow growth stage of production rate was observed before reaching the peak of oil production in Stage Ⅰ.Stage Ⅱ involved a rapid increase in oil retention,with C12-C17 and C24-C32 serving as the primary components,increasing continuously during the pyrolysis process.The generation process involved the cleavage of weak bonds,including bridging bonds(hydroxyl,oxy,peroxy,imino,amino,and nitro),ether bonds,and acid amides in the first stage(Ro=0.50%-0.75%).The carbon chains in aromatic ring structures with heteroatomic functional groups breaks in the second stage(R_(o)=0.75%-1.20%).In the third stage(R_(o)=1.20%-2.50%),the ring structures underwent ring-opening reactions to synthesize iso-short-chain olefins and radicals,while further breakdown of aliphatic chains occurred.By coupling pyrolysis simu-lation experiments and molecular simulation technology,the evolution characteristics and bond breaking mechanism of retained oil in three stages were revealed,providing a reference for the for-mation and evolution mechanism of retained oil.展开更多
Enhancing the ductility and toughness of advanced high-strength steels is essential for the wide range of promising applications.The retained austenite(RA)is a key phase due to the austenite-to-martensite transformati...Enhancing the ductility and toughness of advanced high-strength steels is essential for the wide range of promising applications.The retained austenite(RA)is a key phase due to the austenite-to-martensite transformation and its transformation-induced plasticity effect.It is commonly accepted that slow RA-to-martensite transformation is beneficial to ductility;therefore,the RA fraction and stability should be carefully controlled.The RA stability is related to its morphology,size,carbon content,neighboring phase and orientation.Importantly,these factors are cross-influenced.It is noteworthy that the influence of RA on ductility and fracture toughness is not consistent because of their difference in stress state.There is no clear relationship between fracture toughness and tensile properties.Thus,it is important to understand the role of RA in toughness.The toughness is enhanced during the RA-to-martensite transformation,while the fracture toughness is decreased due to the formation of fresh and brittle martensite.As a result,the findings regarding to the effect of RA on fracture toughness are conflicting.Further investigations should be conducted in order to fully understand the effects of RA on ductility and fracture toughness,which can optimize the combination of ductility and toughness in AHSSs.展开更多
The metastable retained austenite(RA)plays a significant role in the excellent mechanical performance of quenching and partitioning(Q&P)steels,while the volume fraction of RA(V_(RA))is challengeable to directly pr...The metastable retained austenite(RA)plays a significant role in the excellent mechanical performance of quenching and partitioning(Q&P)steels,while the volume fraction of RA(V_(RA))is challengeable to directly predict due to the complicated relationships between the chemical composition and process(like quenching temperature(Qr)).A Gaussian process regression model in machine learning was developed to predict V_(RA),and the model accuracy was further improved by introducing a metallurgical parameter of martensite fraction(fo)to accurately predict V_(RA) in Q&P steels.The developed machine learning model combined with Bayesian global optimization can serve as another selection strategy for the quenching temperature,and this strategy is very effcient as it found the"optimum"Qr with the maximum V_(RA) using only seven consecutive iterations.The benchmark experiment also reveals that the developed machine learning model predicts V_(RA) more accurately than the popular constrained carbon equilibrium thermodynamic model,even better than a thermo-kinetic quenching-partitioning-tempering-local equilibrium model.展开更多
The mechanical properties of the sample and the stability of retained austenite were studied by designing two kinds of ultra-fine bainitic steel with different heat treatment methods austempering above and below Ms(ma...The mechanical properties of the sample and the stability of retained austenite were studied by designing two kinds of ultra-fine bainitic steel with different heat treatment methods austempering above and below Ms(martensite start tem-perature),which were subjected to tensile tests at 20 and 450℃,respectively.The results show that compared to room temperature(20℃)tensile properties,the uniform elongation of the sample at high temperature(450℃)significantly decreased.Specifically,the uniform elongation of the sample austempered above Ms decreased from 8.0%to 3.5%,and the sample austempered below Ms decreased from 10.9%to 3.1%.Additionally,the tensile strength of the sample austempered above Ms significantly decreased(from 1281 to 912 MPa),and the sample austempered below Ms slightly decreased(from 1010 to 974 MPa).This was due to the high carbon content(1.60 wt.%),high mechanical stability,low thermal stability for the retained austenite of the sample austempered below Ms.Besides,the retained austenite decomposed at high temper-atures,the carbon content and transformation driving force were significantly reduced,the transformation rate increased,and the phase transformation content reduced.展开更多
Background: Epidural anesthesia is an effective intervention to treat labor pain and provide analgesia for orthopedic procedures. A rare complication of this technique is epidural catheter retention. Case Presentation...Background: Epidural anesthesia is an effective intervention to treat labor pain and provide analgesia for orthopedic procedures. A rare complication of this technique is epidural catheter retention. Case Presentation: In this case report, we present an otherwise healthy 21-year-old G2P0010 woman at 39 weeks and 3 days gestation whose anesthetic management was complicated by a symptomatic retained epidural catheter fragment. Computed tomography (CT) imaging of her spine showed the fractured catheter within her paraspinal muscles and neurosurgery recommended no surgical intervention at that time. The patient reported resolution of back pain while in the postpartum unit which she continues to endorse two weeks after discharge. Conclusion: Retained epidural catheter is a medical emergency that requires immediate imaging and neurological evaluation. While magnetic resonance imaging is typically regarded as the standard imaging modality for this complication, in epidural sets that contain metallic components, we suggest using CT to avoid the risk of thermal nerve damage. In cases where the patient does not report any acute complaints, nonsurgical management may be appropriate but close follow-up is required to monitor for catheter migration.展开更多
Cadmium(Cd)has seriously affected the quality of traditional Chinese medicinal material Salvia miltiorrhiza in recent years,threatening human health.The physiological and metabolic profiles of S.miltiorrhiza in respon...Cadmium(Cd)has seriously affected the quality of traditional Chinese medicinal material Salvia miltiorrhiza in recent years,threatening human health.The physiological and metabolic profiles of S.miltiorrhiza in response to Cd stress have been revealed in previous studies.However,transcriptional and post-transcriptional regulation in response to different degrees of Cd(0,25,50,and 100 mg/kg)stress in S.miltiorrhiza remains unclear.Here,transcriptome atlas in S.miltiorrhiza under different degrees of Cd Stress was unveiled using RNA sequencing(RNA-seq).These results showed that the profiles of gene expression were different in the response to Cd treatment.Defense response-related biological processes were involved in differentially expressed genes(DEGs).In total,1966 genes were identified as transcription factors(TFs)with seven expressed trends.Retained intron(RI)was the major phenomenon.Targeted genes of intron splicing factors were identified via weighted gene co-expression network analysis(WGCNA).All of these indicated that transcriptional and post-transcriptional regulations were involved in response to Cd stress in S.miltiorrhiza.Our study will provide the most comprehensive resource for studying heavy metals in traditional Chinese medicine plants.展开更多
Background: Detachment of the placenta occurs in about 96% of patients within 30 minutes of completion of the second stage of labour, thus any further delay there after is usually considered as retained placenta. It i...Background: Detachment of the placenta occurs in about 96% of patients within 30 minutes of completion of the second stage of labour, thus any further delay there after is usually considered as retained placenta. It is associated with the risk of post-partum haemorrhage and anaemia. Objectives: To determine the incidence, risk factors, clinical presentation and complications of retained placenta at the study centre during the period under review. Methods: This was a retrospective case-control study in which records of women with retained placenta between January 2011 and December 2015 were retrieved and analysed for their age, parity, risk factors, clinical presentation and associated complications and compared with equal number of patients without retained placenta. Results: There were 11 cases of retained placenta recorded among the total number of 2068 deliveries during the study period, giving an incidence of 0.53% retained placenta in this study. Majority of cases (45.4%) were between age 30 and 39 years which was similar to the controls (54.5%). Most of the cases were unbooked (81%). Similarly, most women in both cases (82%) and controls (73%) were multiparae. All the 5 cases (45.5%) that had post-partum haemorrhage received blood transfusion. The overall incidence of post-partum anaemia was 54%. The average weights of the placentae were significantly smaller in the cases with placental retention (p = 0.010). Conclusion: Retained placenta is associated with significant risks of post-partum haemorrhage and blood transfusion. Non-booking for antenatal care is the commonest risk factor identified for retained placenta in this study.展开更多
[ Objective ] The aim of the research was to reveal the mechanism of Yizhikang powder treatment on dairy cattle with retained placenta from the hemorheological perspective. [ Method] Dairy cattle with retained placent...[ Objective ] The aim of the research was to reveal the mechanism of Yizhikang powder treatment on dairy cattle with retained placenta from the hemorheological perspective. [ Method] Dairy cattle with retained placenta were treated with oral administration of Yizhikang powder. And their hemorheological indexes were measured and compared with the corresponding indicators of pre-administration group, healthy group, and control group （sick but untreated）.[ Result] There was large decrease amplitude in the indexes （whole blood viscosity, plasma viscosity, whole blood viscosity reduction viscosity, ESR, ESR equation K value, fibrinogen content, platelet aggregation rate, RBC deformability IF value） of treated dairy cattle with retained placenta. By t test, the indexes, except hematocrit, decreased significantly after treatment （P〈0.05） and reached the status of post partum healthy cows. The hemorheological indexes didn＇t change significantly in the control group before and after treatment. [ Conclusion] Yizhikang powder could significantly improve blood flow state and reduced the occurrence of qi stagnation and blood stasis in perinatal period.展开更多
The equation which reflects the relationship between the retained austenite and strain has been proposed and clear TRIP can be obtained while the S value (An index of retained austenite stability) is less than 6.5 for...The equation which reflects the relationship between the retained austenite and strain has been proposed and clear TRIP can be obtained while the S value (An index of retained austenite stability) is less than 6.5 for Silicon-Manganese TRIP steel展开更多
The systematic chemical compositions including common C, Si, Mn, Al, and micro-alloying elements of Ti and Nb were designed for high volume fraction of retained austenite as much as possible. The thermo-cycle experime...The systematic chemical compositions including common C, Si, Mn, Al, and micro-alloying elements of Ti and Nb were designed for high volume fraction of retained austenite as much as possible. The thermo-cycle experiments were conducted by using Gleeble 2000 thermo-dynamic test machine for finding the appropriate composition. The experimental results showed that chemical composition had a significant effect on retained austenite, and the appropriate compositions were determined for commercial production of TRIP steels.展开更多
Both microstrueture and mechanical properties of low alloy steels treated by quenching and partitioning （Q＆P） process were examined. The mixed microstructure of martensite and large-fractioned retained austenite （...Both microstrueture and mechanical properties of low alloy steels treated by quenching and partitioning （Q＆P） process were examined. The mixed microstructure of martensite and large-fractioned retained austenite （about 27.3%） was characterized and analyzed, excellent combinations of total elongation of 19% and tensile strength of 1 835 MPa were obtained, and three-stage work hardening behavior was demonstrated during tensile test. The en hanced mechanical properties and work hardening behavior were explained based on the transformation induced plas ticity effect of large fractioned austenite.展开更多
Effects of silicon （Si） content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction （XRD）,transmission electron microscopy （TEM）...Effects of silicon （Si） content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction （XRD）,transmission electron microscopy （TEM）,and other experimental methods.The results show that Si can suppress temper embrittlement,improve temper resistance,and hinder the decomposition of retained austenite.Reversed austenite appears gradually with the increase of Si content during tempering.Si has a significant effect on enhancing carbon （C） partitioning and improving the stability of retained austenite.Si and C atoms are mutually exclusive in lath bainite,while they attract each other in austenite.ε-carbides are found in 1.8wt% Si steel tempered at 250℃,and they get coarsened obviously when tempered at 400℃,leading to temper embrittlement.Not ε-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt% Si steel,which can be inferred as cementites and composite compounds.Temper embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite.展开更多
The presence of retained austenite gives rise to deterioration of the wear resistance and fracture strength of Cr-Mo steels in many cases. Thus, the effects of heat treatments including direct quenching, martempering,...The presence of retained austenite gives rise to deterioration of the wear resistance and fracture strength of Cr-Mo steels in many cases. Thus, the effects of heat treatments including direct quenching, martempering, and austempering on the retained austenite existing in the microstrueture of these steels were investigated. Specimens were austenized at 950 ℃ followed by direct quenching using compressed and still air. The specimens were also isothermally quenched in salt bath at 200 and 300 ℃ for 2, 8, 30, and 120min. Microstructures of the specimens were studied using optical microscope （traditional black and white etching as well as color etching）, scanning electron microscope （SEM）, microhardness tester, and X-ray diffraction （XRD）. The results showed that the lowest amount of retained austenite in the microstructure was obtained in the specimens quenched isothermally at 300 ℃ for 120 min.展开更多
In this work, the effect of prior cold deformation on the stability of retained austenite in GCr15 bearing steel was investigated after quenching and tempering treatment. The thermal stability was evaluated by calcula...In this work, the effect of prior cold deformation on the stability of retained austenite in GCr15 bearing steel was investigated after quenching and tempering treatment. The thermal stability was evaluated by calculating thermal activation energy for decomposition of retained austenite using differential scanning calorimeter. The mechanical stability was investigated according to the strain-induced martensitic transformation behavior of retained austenite under the standard compression testing. It is found that the prior cold deformation not only accelerates the carbide dissolution during the austenitization process but also contributes to the carbon partitioning in the tempering stage due to the higher density of phase boundaries, which results in the improvement of the thermal stability of retained austenite. Due to the enhanced carbide dissolution, the higher carbon content in the prior austenite will intensify the isotropic strain of martensitic transformation. As a consequence, the film-like retained austenite is likely to form under a higher hydrostatic pressure and thus shows a higher mechanical stability. Additionally, it is noteworthy that the benefits of the prior cold deformation to the stability of retained austenite would be saturated when the cold deformation degree is larger than 40%.展开更多
We present a study concerning Fe-0. 176C-1.31Si-1.58Mn-0.26Al-0.3Cr （wt%） steel subjected to a quenching and partitioning （Q＆P） process. The results of scanning electron microscopy, transmission electron microsco...We present a study concerning Fe-0. 176C-1.31Si-1.58Mn-0.26Al-0.3Cr （wt%） steel subjected to a quenching and partitioning （Q＆P） process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demon- strate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite （LB）, and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstrucmre, three types of retained austenite with different sizes and morphologies were observed： blocky retained austenite （-300 nm in width）, film-like retained austenite （80-120 nm in width）, and ul- tra-fine film-like retained austenite （30-40 nm in width）. Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q＆P steel.展开更多
Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry（DSC）.The decomposition curve was abnormal,and the decomposition temperature and the activation...Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry（DSC）.The decomposition curve was abnormal,and the decomposition temperature and the activation energy were measured by the Kissinger method,which were all higher than those in quenched steel.The thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature treatment.It indicated that there is a high thermal stability in retained austenite of the TRIP steel at low temperature,which was also proved by XRD analysis.展开更多
A retained bile duct stone after operation for cholelithiasis still occurs and causes symptoms such as biliary colic and obstructive jaundice.An endoscopic retrograde cholangiopancreatography with endoscopic sphincter...A retained bile duct stone after operation for cholelithiasis still occurs and causes symptoms such as biliary colic and obstructive jaundice.An endoscopic retrograde cholangiopancreatography with endoscopic sphincterotomy(EST),followed by stone extraction,are usually an effective treatment for this condition.However,these procedures are associated with severe complications including pancreatitis,bleeding,and duodenal perforation.Nitrates such as glyceryl trinitrate(GTN) and isosorbide dinitrate(ISDN) are known to relax the sphincter of Oddi.In 6 cases in which a retained stone was detected following cholecystectomy,topical nitrate drip infusion via cystic duct tube(C-tube) was carried out.Retained stones of 2-3 mm diameter and no dilated common bile duct in 3 patients were removed by drip infusion of 50 mg GTN or 10 mg ISDN,which was the regular dose of intravenous injection.Three other cases failed,and EST in 2 cases and endoscopic biliary balloon dilatation in 1 case were performed.One patient developed an adverse event of nausea.Severe complications were not observed.We consider the topical nitrate drip infusion via C-tube to be old but safe,easy,and inexpensive procedure for retained bile duct stone following cholecystectomy,inasmuch as removal rate was about 50% in our cases.展开更多
The effects of finishing rolling temperature and coiling temperature on retained austen-ite were studied for hot-rolled transformation induced plasticity (TRIP) steels with different carbon content. The experimental r...The effects of finishing rolling temperature and coiling temperature on retained austen-ite were studied for hot-rolled transformation induced plasticity (TRIP) steels with different carbon content. The experimental results showed that an appropriate volume fraction of retained austenite from 6% to 11% could be obtained according to the different carbon content less than 0.20% by controlled finishing rolling and coiling for the hot-rolled TRIP steels. It can be concluded that carbon content has a significant effect on the fraction of retained austenite and coiling processing plays stronger role on retaining austenite than fishing rolling processing.展开更多
文摘Corrosion is an essential issue limiting the application of high-strength low-carbon steel in seawater environment. The impact of retained austenite on its corrosion behavior with immersion experiments and related corrosion sensor technology was explored. A model that clarifies the micro-galvanic effect and the heat-induced changes to the shape and composition of retained austenite was used to discuss the findings. The results indicated that retained austenite was generated following an intercritical process and demonstrated approximately 48 mV higher Volta potential than the matrix. The retained austenite content first increased and then decreased with increasing intercritical temperatures, while reaching the maximum value of 8.5% at 660℃. With the increase in retained austenite content, the corrosion rate was increased by up to 32.8% compared to “quenching + tempering” (QT) specimen. The interfaces between the retained austenite and matrix were the priority nucleation sites for corrosion. Moreover, the retained austenite reduced the corrosion resistance of the steel by increasing the micro-galvanic effect and reducing rust layer compactness.
文摘Hydrogen-induced cracking (HIC) is one of the most complex material problems that hydrogen can diffuse into and interact with microstructure, degrading their mechanical properties. Microstructural modification is an effective way to enhance the resistance to HIC. The present study focused on the relationship between the retained austenite (RA) and HIC behavior in NiCrMoV/Nb multi-alloying ultra-strength steel. Results demonstrated that the maximum volume fraction of RA of 9.31% was obtained for QL30T specimen. After the deep cryogenic pretreatment, the volume fraction of RA reduced to 8.8%. RA could reduce the effective diffusion coefficient, while deep cryogenic pretreatment increased the susceptibility of the steel to HIC by a maxim of 14.8%. This was mainly due to the transformation of retained austenite into martensite, degrading the mechanical properties under hydrogen-charged condition. In addition, the deep cryogenic pretreatment had a significant effect on the crack initiation and propagation, with the intergranular (IG) fracture becoming the dominant fracture mode where an increase in the number of secondary cracks in the section. The interfaces of RA and matrix, as well as the grain boundaries, were the preferred sites for cracks initiation.
基金financially supported by the National Natural Science Foundation of China (Grant No. 42072150)
文摘To accurately investigate the evolution characteristics and generation mechanism of retained oil,the study analyzed organic-rich lacustrine shale samples from the Paleogene Kongdian Formation in Cangdong Sag,Bohai Bay Basin.This analysis involves Rock-Eval pyrolysis,pyrolysis simulation experiments,Gas Chromatograph Mass Spectrometer(GC-MS),and reactive molecular dynamics simulations(ReaxFF).The results revealed the retained oil primarily consisted of n-alkanes with carbon numbers ranging from C14 to C36.The generation of retained oil occurred through three stages.A slow growth stage of production rate was observed before reaching the peak of oil production in Stage Ⅰ.Stage Ⅱ involved a rapid increase in oil retention,with C12-C17 and C24-C32 serving as the primary components,increasing continuously during the pyrolysis process.The generation process involved the cleavage of weak bonds,including bridging bonds(hydroxyl,oxy,peroxy,imino,amino,and nitro),ether bonds,and acid amides in the first stage(Ro=0.50%-0.75%).The carbon chains in aromatic ring structures with heteroatomic functional groups breaks in the second stage(R_(o)=0.75%-1.20%).In the third stage(R_(o)=1.20%-2.50%),the ring structures underwent ring-opening reactions to synthesize iso-short-chain olefins and radicals,while further breakdown of aliphatic chains occurred.By coupling pyrolysis simu-lation experiments and molecular simulation technology,the evolution characteristics and bond breaking mechanism of retained oil in three stages were revealed,providing a reference for the for-mation and evolution mechanism of retained oil.
基金supported by the National Natural Science Foundation of China(Nos.52271004 and 51901021).
文摘Enhancing the ductility and toughness of advanced high-strength steels is essential for the wide range of promising applications.The retained austenite(RA)is a key phase due to the austenite-to-martensite transformation and its transformation-induced plasticity effect.It is commonly accepted that slow RA-to-martensite transformation is beneficial to ductility;therefore,the RA fraction and stability should be carefully controlled.The RA stability is related to its morphology,size,carbon content,neighboring phase and orientation.Importantly,these factors are cross-influenced.It is noteworthy that the influence of RA on ductility and fracture toughness is not consistent because of their difference in stress state.There is no clear relationship between fracture toughness and tensile properties.Thus,it is important to understand the role of RA in toughness.The toughness is enhanced during the RA-to-martensite transformation,while the fracture toughness is decreased due to the formation of fresh and brittle martensite.As a result,the findings regarding to the effect of RA on fracture toughness are conflicting.Further investigations should be conducted in order to fully understand the effects of RA on ductility and fracture toughness,which can optimize the combination of ductility and toughness in AHSSs.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(Grant Nos.51771114 and 51371117).
文摘The metastable retained austenite(RA)plays a significant role in the excellent mechanical performance of quenching and partitioning(Q&P)steels,while the volume fraction of RA(V_(RA))is challengeable to directly predict due to the complicated relationships between the chemical composition and process(like quenching temperature(Qr)).A Gaussian process regression model in machine learning was developed to predict V_(RA),and the model accuracy was further improved by introducing a metallurgical parameter of martensite fraction(fo)to accurately predict V_(RA) in Q&P steels.The developed machine learning model combined with Bayesian global optimization can serve as another selection strategy for the quenching temperature,and this strategy is very effcient as it found the"optimum"Qr with the maximum V_(RA) using only seven consecutive iterations.The benchmark experiment also reveals that the developed machine learning model predicts V_(RA) more accurately than the popular constrained carbon equilibrium thermodynamic model,even better than a thermo-kinetic quenching-partitioning-tempering-local equilibrium model.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(52071238)Leading Innovation and Entrepreneurship Team in Zhejiang Province(2021R01020)+2 种基金the Key Research and Development Program of Hubei Province(2021BAA057)Science and Technology Program of Guangxi Province(AA22068080)the 111 Project.
文摘The mechanical properties of the sample and the stability of retained austenite were studied by designing two kinds of ultra-fine bainitic steel with different heat treatment methods austempering above and below Ms(martensite start tem-perature),which were subjected to tensile tests at 20 and 450℃,respectively.The results show that compared to room temperature(20℃)tensile properties,the uniform elongation of the sample at high temperature(450℃)significantly decreased.Specifically,the uniform elongation of the sample austempered above Ms decreased from 8.0%to 3.5%,and the sample austempered below Ms decreased from 10.9%to 3.1%.Additionally,the tensile strength of the sample austempered above Ms significantly decreased(from 1281 to 912 MPa),and the sample austempered below Ms slightly decreased(from 1010 to 974 MPa).This was due to the high carbon content(1.60 wt.%),high mechanical stability,low thermal stability for the retained austenite of the sample austempered below Ms.Besides,the retained austenite decomposed at high temper-atures,the carbon content and transformation driving force were significantly reduced,the transformation rate increased,and the phase transformation content reduced.
文摘Background: Epidural anesthesia is an effective intervention to treat labor pain and provide analgesia for orthopedic procedures. A rare complication of this technique is epidural catheter retention. Case Presentation: In this case report, we present an otherwise healthy 21-year-old G2P0010 woman at 39 weeks and 3 days gestation whose anesthetic management was complicated by a symptomatic retained epidural catheter fragment. Computed tomography (CT) imaging of her spine showed the fractured catheter within her paraspinal muscles and neurosurgery recommended no surgical intervention at that time. The patient reported resolution of back pain while in the postpartum unit which she continues to endorse two weeks after discharge. Conclusion: Retained epidural catheter is a medical emergency that requires immediate imaging and neurological evaluation. While magnetic resonance imaging is typically regarded as the standard imaging modality for this complication, in epidural sets that contain metallic components, we suggest using CT to avoid the risk of thermal nerve damage. In cases where the patient does not report any acute complaints, nonsurgical management may be appropriate but close follow-up is required to monitor for catheter migration.
基金supported by Jiangxi Provincial Natural Science Foundation(20232BAB216119)Science and Technology Research Project of Jiangxi Provincial Department of Education(GJJ2200978)+1 种基金Jiangxi Provincial Health Commission S&T Plan(SKJP220227132)Jiangxi Provincial Administration of Traditional Chinese Medicine S&T Program(2022A392).
文摘Cadmium(Cd)has seriously affected the quality of traditional Chinese medicinal material Salvia miltiorrhiza in recent years,threatening human health.The physiological and metabolic profiles of S.miltiorrhiza in response to Cd stress have been revealed in previous studies.However,transcriptional and post-transcriptional regulation in response to different degrees of Cd(0,25,50,and 100 mg/kg)stress in S.miltiorrhiza remains unclear.Here,transcriptome atlas in S.miltiorrhiza under different degrees of Cd Stress was unveiled using RNA sequencing(RNA-seq).These results showed that the profiles of gene expression were different in the response to Cd treatment.Defense response-related biological processes were involved in differentially expressed genes(DEGs).In total,1966 genes were identified as transcription factors(TFs)with seven expressed trends.Retained intron(RI)was the major phenomenon.Targeted genes of intron splicing factors were identified via weighted gene co-expression network analysis(WGCNA).All of these indicated that transcriptional and post-transcriptional regulations were involved in response to Cd stress in S.miltiorrhiza.Our study will provide the most comprehensive resource for studying heavy metals in traditional Chinese medicine plants.
文摘Background: Detachment of the placenta occurs in about 96% of patients within 30 minutes of completion of the second stage of labour, thus any further delay there after is usually considered as retained placenta. It is associated with the risk of post-partum haemorrhage and anaemia. Objectives: To determine the incidence, risk factors, clinical presentation and complications of retained placenta at the study centre during the period under review. Methods: This was a retrospective case-control study in which records of women with retained placenta between January 2011 and December 2015 were retrieved and analysed for their age, parity, risk factors, clinical presentation and associated complications and compared with equal number of patients without retained placenta. Results: There were 11 cases of retained placenta recorded among the total number of 2068 deliveries during the study period, giving an incidence of 0.53% retained placenta in this study. Majority of cases (45.4%) were between age 30 and 39 years which was similar to the controls (54.5%). Most of the cases were unbooked (81%). Similarly, most women in both cases (82%) and controls (73%) were multiparae. All the 5 cases (45.5%) that had post-partum haemorrhage received blood transfusion. The overall incidence of post-partum anaemia was 54%. The average weights of the placentae were significantly smaller in the cases with placental retention (p = 0.010). Conclusion: Retained placenta is associated with significant risks of post-partum haemorrhage and blood transfusion. Non-booking for antenatal care is the commonest risk factor identified for retained placenta in this study.
基金Supported by Science and Technology Key Projects of Xinjiang Pro-duction and Construction Corps (2006GG22)~~
文摘[ Objective ] The aim of the research was to reveal the mechanism of Yizhikang powder treatment on dairy cattle with retained placenta from the hemorheological perspective. [ Method] Dairy cattle with retained placenta were treated with oral administration of Yizhikang powder. And their hemorheological indexes were measured and compared with the corresponding indicators of pre-administration group, healthy group, and control group （sick but untreated）.[ Result] There was large decrease amplitude in the indexes （whole blood viscosity, plasma viscosity, whole blood viscosity reduction viscosity, ESR, ESR equation K value, fibrinogen content, platelet aggregation rate, RBC deformability IF value） of treated dairy cattle with retained placenta. By t test, the indexes, except hematocrit, decreased significantly after treatment （P〈0.05） and reached the status of post partum healthy cows. The hemorheological indexes didn＇t change significantly in the control group before and after treatment. [ Conclusion] Yizhikang powder could significantly improve blood flow state and reduced the occurrence of qi stagnation and blood stasis in perinatal period.
文摘The equation which reflects the relationship between the retained austenite and strain has been proposed and clear TRIP can be obtained while the S value (An index of retained austenite stability) is less than 6.5 for Silicon-Manganese TRIP steel
文摘The systematic chemical compositions including common C, Si, Mn, Al, and micro-alloying elements of Ti and Nb were designed for high volume fraction of retained austenite as much as possible. The thermo-cycle experiments were conducted by using Gleeble 2000 thermo-dynamic test machine for finding the appropriate composition. The experimental results showed that chemical composition had a significant effect on retained austenite, and the appropriate compositions were determined for commercial production of TRIP steels.
基金Item Sponsored by Youth Science Funds of China(51101036)National Basic Research Program of China(2010CB630803)National Key Technology Support Program of China(2013BAE07B05)
文摘Both microstrueture and mechanical properties of low alloy steels treated by quenching and partitioning （Q＆P） process were examined. The mixed microstructure of martensite and large-fractioned retained austenite （about 27.3%） was characterized and analyzed, excellent combinations of total elongation of 19% and tensile strength of 1 835 MPa were obtained, and three-stage work hardening behavior was demonstrated during tensile test. The en hanced mechanical properties and work hardening behavior were explained based on the transformation induced plas ticity effect of large fractioned austenite.
基金supported by the Project of Scientific and Technical Supporting Program of China during the 11th Five-Year Plan(No.2006BAE03A06)
文摘Effects of silicon （Si） content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction （XRD）,transmission electron microscopy （TEM）,and other experimental methods.The results show that Si can suppress temper embrittlement,improve temper resistance,and hinder the decomposition of retained austenite.Reversed austenite appears gradually with the increase of Si content during tempering.Si has a significant effect on enhancing carbon （C） partitioning and improving the stability of retained austenite.Si and C atoms are mutually exclusive in lath bainite,while they attract each other in austenite.ε-carbides are found in 1.8wt% Si steel tempered at 250℃,and they get coarsened obviously when tempered at 400℃,leading to temper embrittlement.Not ε-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt% Si steel,which can be inferred as cementites and composite compounds.Temper embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite.
文摘The presence of retained austenite gives rise to deterioration of the wear resistance and fracture strength of Cr-Mo steels in many cases. Thus, the effects of heat treatments including direct quenching, martempering, and austempering on the retained austenite existing in the microstrueture of these steels were investigated. Specimens were austenized at 950 ℃ followed by direct quenching using compressed and still air. The specimens were also isothermally quenched in salt bath at 200 and 300 ℃ for 2, 8, 30, and 120min. Microstructures of the specimens were studied using optical microscope （traditional black and white etching as well as color etching）, scanning electron microscope （SEM）, microhardness tester, and X-ray diffraction （XRD）. The results showed that the lowest amount of retained austenite in the microstructure was obtained in the specimens quenched isothermally at 300 ℃ for 120 min.
基金supported by the National Natural Science Foundation of China (Nos. 51575414 and 51605354)the 111 Project (B17034), the China Postdoctoral Science Foundation (No. 2017M612524)the State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (P2019-017)
文摘In this work, the effect of prior cold deformation on the stability of retained austenite in GCr15 bearing steel was investigated after quenching and tempering treatment. The thermal stability was evaluated by calculating thermal activation energy for decomposition of retained austenite using differential scanning calorimeter. The mechanical stability was investigated according to the strain-induced martensitic transformation behavior of retained austenite under the standard compression testing. It is found that the prior cold deformation not only accelerates the carbide dissolution during the austenitization process but also contributes to the carbon partitioning in the tempering stage due to the higher density of phase boundaries, which results in the improvement of the thermal stability of retained austenite. Due to the enhanced carbide dissolution, the higher carbon content in the prior austenite will intensify the isotropic strain of martensitic transformation. As a consequence, the film-like retained austenite is likely to form under a higher hydrostatic pressure and thus shows a higher mechanical stability. Additionally, it is noteworthy that the benefits of the prior cold deformation to the stability of retained austenite would be saturated when the cold deformation degree is larger than 40%.
基金funded by the China Scholarship Council (No. 201406460053)
文摘We present a study concerning Fe-0. 176C-1.31Si-1.58Mn-0.26Al-0.3Cr （wt%） steel subjected to a quenching and partitioning （Q＆P） process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demon- strate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite （LB）, and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstrucmre, three types of retained austenite with different sizes and morphologies were observed： blocky retained austenite （-300 nm in width）, film-like retained austenite （80-120 nm in width）, and ul- tra-fine film-like retained austenite （30-40 nm in width）. Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q＆P steel.
基金Item Sponsored by National Natural Science Foundation of China(50171038)Belgium-China Bilateral Project BIL04/13
文摘Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry（DSC）.The decomposition curve was abnormal,and the decomposition temperature and the activation energy were measured by the Kissinger method,which were all higher than those in quenched steel.The thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature treatment.It indicated that there is a high thermal stability in retained austenite of the TRIP steel at low temperature,which was also proved by XRD analysis.
文摘A retained bile duct stone after operation for cholelithiasis still occurs and causes symptoms such as biliary colic and obstructive jaundice.An endoscopic retrograde cholangiopancreatography with endoscopic sphincterotomy(EST),followed by stone extraction,are usually an effective treatment for this condition.However,these procedures are associated with severe complications including pancreatitis,bleeding,and duodenal perforation.Nitrates such as glyceryl trinitrate(GTN) and isosorbide dinitrate(ISDN) are known to relax the sphincter of Oddi.In 6 cases in which a retained stone was detected following cholecystectomy,topical nitrate drip infusion via cystic duct tube(C-tube) was carried out.Retained stones of 2-3 mm diameter and no dilated common bile duct in 3 patients were removed by drip infusion of 50 mg GTN or 10 mg ISDN,which was the regular dose of intravenous injection.Three other cases failed,and EST in 2 cases and endoscopic biliary balloon dilatation in 1 case were performed.One patient developed an adverse event of nausea.Severe complications were not observed.We consider the topical nitrate drip infusion via C-tube to be old but safe,easy,and inexpensive procedure for retained bile duct stone following cholecystectomy,inasmuch as removal rate was about 50% in our cases.
文摘The effects of finishing rolling temperature and coiling temperature on retained austen-ite were studied for hot-rolled transformation induced plasticity (TRIP) steels with different carbon content. The experimental results showed that an appropriate volume fraction of retained austenite from 6% to 11% could be obtained according to the different carbon content less than 0.20% by controlled finishing rolling and coiling for the hot-rolled TRIP steels. It can be concluded that carbon content has a significant effect on the fraction of retained austenite and coiling processing plays stronger role on retaining austenite than fishing rolling processing.
