[Objectives]To determine the content of hyperin and luteolin in Vernonia cinerea(L.)Less.,and to provide basic experimental data for experimental research and clinical application of V.cinerea(L.)Less.[Methods]The com...[Objectives]To determine the content of hyperin and luteolin in Vernonia cinerea(L.)Less.,and to provide basic experimental data for experimental research and clinical application of V.cinerea(L.)Less.[Methods]The components to be determined were extracted by ultrasonic extraction,and the hyperin and luteolin in V.cinerea(L.)Less.were separated and determined by reversed-phase high performance liquid chromatography(chromatographic conditions:reverse C 18 column,methanol-0.4%phosphoric acid as mobile phase for gradient elution,flow rate of 1.0 mL/min,detector wavelength of 360 nm).[Results]The precision and repeatability of the experimental method were good,and the solution of V.cinerea(L.)Less.was stable within 18 h.There was a good linear relationship between the injection volume of hyperin and luteolin and the chromatographic peak area within the prescribed range,and the recovery rate was qualified.The content of hyperin and luteolin in V.cinerea(L.)Less.was 0.0665 mg/g(n=3)and 0.1004 mg/g(n=3),respectively.[Conclusions]The experimental method is sensitive,specific,stable,accurate and reliable,and can be used for the determination of hyperin and luteolin in V.cinerea(L.)Less.展开更多
In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The ...In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The microstructure and solidification kinetics of the two as-cast grades were in situ observed by high temperature confocal laser scanning microscopy(HT-CLSM).There are significant differences in the as-cast microstructures of the two 316L stainless steel compositions.In L-316L steel,ferrite morphology appears as the short rods with a ferrite content of 6.98%,forming a dual-phase microstructure consisting of austenite and ferrite.Conversely,in H-316L steel,the ferrite appears as discontinuous network structures with a content of 4.41%,forming a microstructure composed of austenite and sigma(σ)phase.The alloying elements in H-316L steel exhibit a complex distribution,with Ni and Mo enriching at the austenite grain boundaries.HT-CLSM experiments provide the real-time observation of the solidification processes of both 316L specimens and reveal distinct solidification modes:L-316L steel solidifies in an FA mode,whereas H-316L steel solidifies in an AF mode.These differences result in ferrite and austenite predominantly serving as the nucleation and growth phases,respectively.The solidification mode observed by experiments is similar to the thermodynamic calculation results.The L-316L steel solidified in the FA mode and showed minimal element segregation,which lead to a direct transformation of ferrite to austenite phase(δ→γ)during phase transformation after solidification.Besides,the H-316L steel solidified in the AF mode and showed severe element segregation,which lead to Mo enrichment at grain boundaries and transformation of ferrite into sigma and austenite phases through the eutectoid reaction(δ→σ+γ).展开更多
Postharvest rot of blueberry fruits caused by Botrytis cinerea led to huge economic losses in storage and transportation.In this study,Metschnikowia pulcherrima T-2 was isolated from the surface of blueberry fruits an...Postharvest rot of blueberry fruits caused by Botrytis cinerea led to huge economic losses in storage and transportation.In this study,Metschnikowia pulcherrima T-2 was isolated from the surface of blueberry fruits and significantly reduced postharvest rot of blueberry fruits.The weight loss rate of T-2 soaked blueberry fruits was decreased;the contents of total soluble solids,titratable acidity and vitamin C of T-2 treated blueberry fruits were increased at a humidity of 85% and 25℃.T-2 also enhanced the control of gray mold in blueberry fruits,but could not directly inhibit the growth of B.cinerea in vitro.The volatile organic compounds(VOCs)produced by T-2 could inhibit the growth of B.cinerea,and significantly reduced the postharvest rot of blueberry fruits.According to Gas Chromatography-Mass Spectrometry(GC-MS)analysis and antibacterial analysis,the benzyl alcohol,phenylethyl alcohol,benzaldehyde,2-ethyl-1-hexanol,acetic acid,octanoic acid,3-hydroxy-2-butanone,2,5-dimethyl-pyrazine and isoamyl acetate were selected.The influence of the above 9 volatiles on B.cinerea growth was assessed by treating B.cinerea in vitro with various concentrations of volatile.The lowest effective amounts of 9 volatiles were established to reduce the postharvest rot of blueberry fruits.These results shed light on the roles of T-2 VOCs in the control of postharvest blueberry fruits to B.cinerea,and provided a new method of postharvest storage.展开更多
The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environme...The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environment before and after the transformation.The effect of the inclusion transformation on the pitting corrosion behavior of 316L stainless steel and its intrinsic mechanism was also revealed.Results revealed a gradual transformation of MnO-SiO_(2)inclusions into MnO-Cr_(2)O_(3) within the temperature range of 1373 to 1573 K.MnO-Cr_(2)O_(3)inclusions exhibited minimal dissolution in chloride ion corrosion environments,while MnO-SiO_(2)oxides demonstrated higher electrochemical activity and were more prone to dissolve and form pits.Meanwhile,IHT significantly reduced the dislocation density of stainless steel,rendering it more stable in corrosive environments.X-ray photoelectron spectroscopy peak distributions of the passive films demonstrated that IHT increased the proportion of Cr and Fe oxides and hydroxides in the passive film which improved the stability and corrosion resistance of the steel.展开更多
Stainless steel parts with complex shape can be fabricated using additive manufacturing,which do not rely on molds and dies.However,coarse dendrites induced by repeated heating of additive manufacturing result in weak...Stainless steel parts with complex shape can be fabricated using additive manufacturing,which do not rely on molds and dies.However,coarse dendrites induced by repeated heating of additive manufacturing result in weak properties,which limits its application.In this study,an in-situ ultrasonic rolling(UR)device was developed to assist the laser directed energy deposition(LDED)process.The microstructural characteristics,as well as the microhardness and wear behavior,were studied for the 316L stainless steel manufactured by in-situ ultrasonic rolling assisted LDED.It is found that austenite,ferrite,and small Si oxides are the main constituents of both the LDED and LDED-UR alloy samples.Under the severe plastic deformation of ultrasonic rolling,the long-branched ferrites by LDED are transformed into the rod-like phases by LDED-UR.Meanwhile,the ferrite is more uniformly distributed in the LDED-UR alloy sample compared with that in LDED alloy sample.Columnar grains with the size of 97.85μm appear in the LDED alloy sample,which is larger than the fully equiaxed grains(22.35μm)of the LDED-UR alloy.The hardness of the LDED-UR alloy sample is about 266.13±13.62 HV_(0.2),which is larger than that of the LDED alloy sample(212.93±12.85 HV_(0.2)).Meanwhile,the wear resistance is also greatly enhanced by applying the assisted in-situ ultrasonic rolling.The achieved high wear resistance can be ascribed to the uniformly distributed hard matter(ferrites)and the impedance of dislocations by high fraction of grain boundaries.Abrasive wear and adhesive wear are identified as the primary wear mechanisms of the studied alloy.Gaining an in-depth understanding of the relationship between wear mechanisms and microstructures offers an effective approach in manufacturing high wear resistant alloys suitable for use in harsh working environments.展开更多
Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposite...Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposited alloys.This study introduced in-situ ultrasonic rolling(UR)as an innovative method to enhance the corrosion resistance of LDED specimens,and the microstructural characteristics and their correlation with corrosion resistance were deeply investigated.The findings reveal that the LDED-UR specimen exhibits a reduction in both the fraction and size of pores.Under the influence of severe plastic deformation generated by LDED-UR process,fully equiaxed grains appear with a reduced average size of 28.61μm(compared to63.98μm for the LDED specimen with columnar grains).The electrochemical corrosion resistance of the LDED-UR specimen is significantly enhanced compared to the LDED specimen.This enhanced corrosion resistance can be attributed to the low fraction of small-sized pores,the fine and uniformly distributed Cr-enriched ferrite phase,and the formation of a compact and thick passive film due to dense grain boundaries.The insight of the correlation between microstructure and corrosion behavior opens up a new pathway to enhance the corrosion resistance of LDED specimens.展开更多
Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Bori...Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.展开更多
Digital light processing(DLP)is widely used in ceramic additive manufacturing.However,it remains unexplored for metals.In this study,the regulatory mechanisms of the microstructure and mechanical properties of AISI 31...Digital light processing(DLP)is widely used in ceramic additive manufacturing.However,it remains unexplored for metals.In this study,the regulatory mechanisms of the microstructure and mechanical properties of AISI 316L stainless steel were investigated by optimizing a DLP-compatible metal slurry formulation and sintering process.A photosensitive resin system(mass ratio of 5:1:2:2 for U600,LA,ACMO,and HDDA,respectively)with 88 wt%solid content is designed to achieve a slurry with balanced rheology,photocurability,and low pyrolysis residue.Compared to vacuum sintering,which leads to brittle fracture of material,the Ar/H2 mixed gas(5%H2)effectively reduces carbon and oxygen impurities via reduction,mitigating carbide and oxide segregation at grain boundaries and within grains,thereby enhancing strength-ductility.In addition,the prolonged high-temperature sintering inducesδ-ferrite precipitation at grain boundaries,which fills residual pores to improve densification obviously.Under optimized sintering conditions(Ar/H2,1380°C,6 h),the material achieves 96.2%relative density with tensile strength and fracture elongation of 543.5 MPa and 58.7%,respectively,exhibiting uniform dimple-dominated fracture morphology.This synergistic optimization of the slurry formulation and sintering parameters improves the strength-ductility balance in DLP-fabricated metal materials,offering theoretical and technical insights for the additive manufacturing of complex high-performance metal components.展开更多
An investigation on the tensile properties and strengthening mechanism of a dense 316L stainless steel(316LSS)material fabricated by laser powder bed fusion(L-PBF)has been conducted with varying heat treatment conditi...An investigation on the tensile properties and strengthening mechanism of a dense 316L stainless steel(316LSS)material fabricated by laser powder bed fusion(L-PBF)has been conducted with varying heat treatment conditions.Deformation mechanisms of as-built and heat-treated samples were elucidated through multiscale microscopy characterizations.The cellular structure characterized by high density dislocation provided a strong barrier to the dislocation propagation,enhancing the yield strength of L-PBF 316LSS.Additionally,the accumulation of free dislocations at grain boundaries triggered the initiation of deformation twins and synergistically interacted with the dislocation wall to establish a three-dimensional network pinning structure,thereby effectively improving the continuous work hardening capability of the as-built sample.In contrast,the absence of cellular structure in HT 1000 samples resulted in a 21.8%reduction in yield strength and a 12%increase in elongation,exhibiting typical strength-ductility trade-off.The absence of cellular structure facilitated the formation of more deformation twins and contributed to the manifestation of the dynamic Hall–Petch effect.It effectively extended the work hardening regime of L-PBF 316LSS,thereby delaying the necking and enhancing its plasticity.Importantly,the Hall–Petch constant has been modified by analyzing the dependence of resolved shear yield strength,which originated from the cellular structure,on the inverse square root of cell size(d−1/2).The modified Hall–Petch relationship accurately assessed the contribution of cellular structure to the yield strength of L-PBF 316LSS.The underlying strengthening mechanism of cellular structure was comprehensively revealed,and valuable insights for further optimization and enhancement of the mechanical properties of L-PBF 316LSS were offered.展开更多
基金Supported by Independent Research Project of Key Laboratory of Extraction,Purification and Quality Analysis of Traditional Chinese Medicine in Guangxi Universities(J1606701).
文摘[Objectives]To determine the content of hyperin and luteolin in Vernonia cinerea(L.)Less.,and to provide basic experimental data for experimental research and clinical application of V.cinerea(L.)Less.[Methods]The components to be determined were extracted by ultrasonic extraction,and the hyperin and luteolin in V.cinerea(L.)Less.were separated and determined by reversed-phase high performance liquid chromatography(chromatographic conditions:reverse C 18 column,methanol-0.4%phosphoric acid as mobile phase for gradient elution,flow rate of 1.0 mL/min,detector wavelength of 360 nm).[Results]The precision and repeatability of the experimental method were good,and the solution of V.cinerea(L.)Less.was stable within 18 h.There was a good linear relationship between the injection volume of hyperin and luteolin and the chromatographic peak area within the prescribed range,and the recovery rate was qualified.The content of hyperin and luteolin in V.cinerea(L.)Less.was 0.0665 mg/g(n=3)and 0.1004 mg/g(n=3),respectively.[Conclusions]The experimental method is sensitive,specific,stable,accurate and reliable,and can be used for the determination of hyperin and luteolin in V.cinerea(L.)Less.
基金support of the Research Project Supported by Shanxi Scholarship Council of China(2022-040)"Chunhui Plan"Collaborative Research Project by the Ministry of Education of China(HZKY20220507)+2 种基金National Natural Science Foundation of China(52104338)Applied Fundamental Research Programs of Shanxi Province(202303021221036)Shandong Postdoctoral Science Foundation(SDCX-ZG-202303027,SDBX2023054).
文摘In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The microstructure and solidification kinetics of the two as-cast grades were in situ observed by high temperature confocal laser scanning microscopy(HT-CLSM).There are significant differences in the as-cast microstructures of the two 316L stainless steel compositions.In L-316L steel,ferrite morphology appears as the short rods with a ferrite content of 6.98%,forming a dual-phase microstructure consisting of austenite and ferrite.Conversely,in H-316L steel,the ferrite appears as discontinuous network structures with a content of 4.41%,forming a microstructure composed of austenite and sigma(σ)phase.The alloying elements in H-316L steel exhibit a complex distribution,with Ni and Mo enriching at the austenite grain boundaries.HT-CLSM experiments provide the real-time observation of the solidification processes of both 316L specimens and reveal distinct solidification modes:L-316L steel solidifies in an FA mode,whereas H-316L steel solidifies in an AF mode.These differences result in ferrite and austenite predominantly serving as the nucleation and growth phases,respectively.The solidification mode observed by experiments is similar to the thermodynamic calculation results.The L-316L steel solidified in the FA mode and showed minimal element segregation,which lead to a direct transformation of ferrite to austenite phase(δ→γ)during phase transformation after solidification.Besides,the H-316L steel solidified in the AF mode and showed severe element segregation,which lead to Mo enrichment at grain boundaries and transformation of ferrite into sigma and austenite phases through the eutectoid reaction(δ→σ+γ).
基金supported by the Scientific Project of Tianjin Municipal Education Commission(Grant No.2021KJ105)。
文摘Postharvest rot of blueberry fruits caused by Botrytis cinerea led to huge economic losses in storage and transportation.In this study,Metschnikowia pulcherrima T-2 was isolated from the surface of blueberry fruits and significantly reduced postharvest rot of blueberry fruits.The weight loss rate of T-2 soaked blueberry fruits was decreased;the contents of total soluble solids,titratable acidity and vitamin C of T-2 treated blueberry fruits were increased at a humidity of 85% and 25℃.T-2 also enhanced the control of gray mold in blueberry fruits,but could not directly inhibit the growth of B.cinerea in vitro.The volatile organic compounds(VOCs)produced by T-2 could inhibit the growth of B.cinerea,and significantly reduced the postharvest rot of blueberry fruits.According to Gas Chromatography-Mass Spectrometry(GC-MS)analysis and antibacterial analysis,the benzyl alcohol,phenylethyl alcohol,benzaldehyde,2-ethyl-1-hexanol,acetic acid,octanoic acid,3-hydroxy-2-butanone,2,5-dimethyl-pyrazine and isoamyl acetate were selected.The influence of the above 9 volatiles on B.cinerea growth was assessed by treating B.cinerea in vitro with various concentrations of volatile.The lowest effective amounts of 9 volatiles were established to reduce the postharvest rot of blueberry fruits.These results shed light on the roles of T-2 VOCs in the control of postharvest blueberry fruits to B.cinerea,and provided a new method of postharvest storage.
基金the support from the National Natural Science Foundation of China(Grant Nos.52074198,52374342,and U21A20113)the Department of Science and Technology of Hubei Province(Grant Nos.2023AFB603 and 2023DJC140).
文摘The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environment before and after the transformation.The effect of the inclusion transformation on the pitting corrosion behavior of 316L stainless steel and its intrinsic mechanism was also revealed.Results revealed a gradual transformation of MnO-SiO_(2)inclusions into MnO-Cr_(2)O_(3) within the temperature range of 1373 to 1573 K.MnO-Cr_(2)O_(3)inclusions exhibited minimal dissolution in chloride ion corrosion environments,while MnO-SiO_(2)oxides demonstrated higher electrochemical activity and were more prone to dissolve and form pits.Meanwhile,IHT significantly reduced the dislocation density of stainless steel,rendering it more stable in corrosive environments.X-ray photoelectron spectroscopy peak distributions of the passive films demonstrated that IHT increased the proportion of Cr and Fe oxides and hydroxides in the passive film which improved the stability and corrosion resistance of the steel.
基金supports from the National Natural Science Foundation of China(No.52305440)the Natural Science Foundation of Changsha City(Nos.kq2208272,kq2208274)+1 种基金the Tribology Science Fund of the State Key Laboratory of Tribology in Advanced Equipment(No.SKLTKF22B09)the National Key Research and Development Program of China(No.2022YFB3706902)were acknowledged.
文摘Stainless steel parts with complex shape can be fabricated using additive manufacturing,which do not rely on molds and dies.However,coarse dendrites induced by repeated heating of additive manufacturing result in weak properties,which limits its application.In this study,an in-situ ultrasonic rolling(UR)device was developed to assist the laser directed energy deposition(LDED)process.The microstructural characteristics,as well as the microhardness and wear behavior,were studied for the 316L stainless steel manufactured by in-situ ultrasonic rolling assisted LDED.It is found that austenite,ferrite,and small Si oxides are the main constituents of both the LDED and LDED-UR alloy samples.Under the severe plastic deformation of ultrasonic rolling,the long-branched ferrites by LDED are transformed into the rod-like phases by LDED-UR.Meanwhile,the ferrite is more uniformly distributed in the LDED-UR alloy sample compared with that in LDED alloy sample.Columnar grains with the size of 97.85μm appear in the LDED alloy sample,which is larger than the fully equiaxed grains(22.35μm)of the LDED-UR alloy.The hardness of the LDED-UR alloy sample is about 266.13±13.62 HV_(0.2),which is larger than that of the LDED alloy sample(212.93±12.85 HV_(0.2)).Meanwhile,the wear resistance is also greatly enhanced by applying the assisted in-situ ultrasonic rolling.The achieved high wear resistance can be ascribed to the uniformly distributed hard matter(ferrites)and the impedance of dislocations by high fraction of grain boundaries.Abrasive wear and adhesive wear are identified as the primary wear mechanisms of the studied alloy.Gaining an in-depth understanding of the relationship between wear mechanisms and microstructures offers an effective approach in manufacturing high wear resistant alloys suitable for use in harsh working environments.
基金financial supports from the National Natural Science Foundation of China (No.52305440)the Natural Science Foundation of Changsha City (Nos.kq2208272,kq2208274)+1 种基金the Tribology Science Fund of the State Key Laboratory of Tribology in Advanced Equipment (SKLTKF22B09)the National Key Research and Development Program of China (2022YFB3706902)。
文摘Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposited alloys.This study introduced in-situ ultrasonic rolling(UR)as an innovative method to enhance the corrosion resistance of LDED specimens,and the microstructural characteristics and their correlation with corrosion resistance were deeply investigated.The findings reveal that the LDED-UR specimen exhibits a reduction in both the fraction and size of pores.Under the influence of severe plastic deformation generated by LDED-UR process,fully equiaxed grains appear with a reduced average size of 28.61μm(compared to63.98μm for the LDED specimen with columnar grains).The electrochemical corrosion resistance of the LDED-UR specimen is significantly enhanced compared to the LDED specimen.This enhanced corrosion resistance can be attributed to the low fraction of small-sized pores,the fine and uniformly distributed Cr-enriched ferrite phase,and the formation of a compact and thick passive film due to dense grain boundaries.The insight of the correlation between microstructure and corrosion behavior opens up a new pathway to enhance the corrosion resistance of LDED specimens.
文摘Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.
基金supported by National Natural Science Foundation of China(Grant Nos.52205231,52205196)Taishan Scholars Program,and Research Project of Shandong Laboratory of Advanced Materials and Green Manufacturing at Yantai(Grant Nos.AMGM0613,AMGM0620).
文摘Digital light processing(DLP)is widely used in ceramic additive manufacturing.However,it remains unexplored for metals.In this study,the regulatory mechanisms of the microstructure and mechanical properties of AISI 316L stainless steel were investigated by optimizing a DLP-compatible metal slurry formulation and sintering process.A photosensitive resin system(mass ratio of 5:1:2:2 for U600,LA,ACMO,and HDDA,respectively)with 88 wt%solid content is designed to achieve a slurry with balanced rheology,photocurability,and low pyrolysis residue.Compared to vacuum sintering,which leads to brittle fracture of material,the Ar/H2 mixed gas(5%H2)effectively reduces carbon and oxygen impurities via reduction,mitigating carbide and oxide segregation at grain boundaries and within grains,thereby enhancing strength-ductility.In addition,the prolonged high-temperature sintering inducesδ-ferrite precipitation at grain boundaries,which fills residual pores to improve densification obviously.Under optimized sintering conditions(Ar/H2,1380°C,6 h),the material achieves 96.2%relative density with tensile strength and fracture elongation of 543.5 MPa and 58.7%,respectively,exhibiting uniform dimple-dominated fracture morphology.This synergistic optimization of the slurry formulation and sintering parameters improves the strength-ductility balance in DLP-fabricated metal materials,offering theoretical and technical insights for the additive manufacturing of complex high-performance metal components.
基金supported by the National Natural Science Foundation of China(Grant Nos.52074198,52374342 and U21A20113)also supported by the Department of Science and Technology of Hubei Province(Grant Nos.2023AFB603 and 2023DJC140)The Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education,Wuhan University of Science and Technology(Grant No.FMRUlab23-01)is also greatly appreciated.
文摘An investigation on the tensile properties and strengthening mechanism of a dense 316L stainless steel(316LSS)material fabricated by laser powder bed fusion(L-PBF)has been conducted with varying heat treatment conditions.Deformation mechanisms of as-built and heat-treated samples were elucidated through multiscale microscopy characterizations.The cellular structure characterized by high density dislocation provided a strong barrier to the dislocation propagation,enhancing the yield strength of L-PBF 316LSS.Additionally,the accumulation of free dislocations at grain boundaries triggered the initiation of deformation twins and synergistically interacted with the dislocation wall to establish a three-dimensional network pinning structure,thereby effectively improving the continuous work hardening capability of the as-built sample.In contrast,the absence of cellular structure in HT 1000 samples resulted in a 21.8%reduction in yield strength and a 12%increase in elongation,exhibiting typical strength-ductility trade-off.The absence of cellular structure facilitated the formation of more deformation twins and contributed to the manifestation of the dynamic Hall–Petch effect.It effectively extended the work hardening regime of L-PBF 316LSS,thereby delaying the necking and enhancing its plasticity.Importantly,the Hall–Petch constant has been modified by analyzing the dependence of resolved shear yield strength,which originated from the cellular structure,on the inverse square root of cell size(d−1/2).The modified Hall–Petch relationship accurately assessed the contribution of cellular structure to the yield strength of L-PBF 316LSS.The underlying strengthening mechanism of cellular structure was comprehensively revealed,and valuable insights for further optimization and enhancement of the mechanical properties of L-PBF 316LSS were offered.
