Ultra-high strength steels with a strength level of 2000 MPa are critical structural materials for some extreme service environments but face problems of low ductility and bad toughness.Current research effort s often...Ultra-high strength steels with a strength level of 2000 MPa are critical structural materials for some extreme service environments but face problems of low ductility and bad toughness.Current research effort s often focus on improving individual property,such as elongation or toughness.Therefore,it re-mains a significant challenge to unify both features of high strength,high ductility,and high toughness in one material.Adding precious metals such as Ni and Co and using aging treatment can achieve good strength and ductility in the maraging steels,but the cost is too high.In this study,we report a lean 2.4 GPa ultra-high-strength steel with a uniform elongation of 7.7%and a V-notched impact toughness of 29 J/cm^(2),which shows a competitive advantage compared with existing aircraft landing gear steels.The alloy composition design of“Mn+microalloying”and simple possessing route of quenching,deep cryo-genic treatment,and low-temperature annealing(Q-D-L)are used to achieve low-cost preparation.The transformation behaviors and mechanisms of strengthening,ductilizing,and toughening are discussed.The developed steel possesses a fine banded-equiaxed heterogeneous original austenite structure,where the CP4 occupies most of the equiaxed austenite,with more high-angle grain boundaries,and the marten-sitic variant of the banded structure is selectively weakened,resulting in a more uniform deformation,so that the crack nucleation energy and propagation energy can be simultaneously improved.Besides,the low aspect ratio structure originating from the fine parent austenite is beneficial to stimulating out-of-lath plane and in-lath plane multiple slip systems,compared with the coarse martensite with geometric lath constraints,thus increasing the deformation capability of martensite.Consequently,with the yield strength of the sample increased to 1960 MPa,the uniform elongation remained as high as 7.7%,indi-cating a notable improvement in both strength and ductility compared to samples with coarse banded austenite structures(1718 MPa&7.6%).This study provides new insights into alloy design and processing strategies for the synergistic enhancement of multiple properties in ultra-high-strength steels.展开更多
Immobilization of alcalase on a ZIF-L(A@ZIF-L)support was explored for its potential application in producing hydrolysates of proteins extracted from microalgae.The immobilized enzyme was characterized using FTIR,XRD,...Immobilization of alcalase on a ZIF-L(A@ZIF-L)support was explored for its potential application in producing hydrolysates of proteins extracted from microalgae.The immobilized enzyme was characterized using FTIR,XRD,SEM,and TGA,and the maximum adsorption capacity was found to be 672.1±5.5 mg g^(-1)at 40℃.Adsorption equilibrium data indicated that alcalase physically adsorbed onto the ZIF-L,with the isotherm well described by the Freundlich model.The adsorption kinetics aligned best with the pseudo-first order model,suggesting that both film and intraparticle diffusion were significant.The hydrolytic activity of the immobilized A@ZIF-L was initially tested using BSA as a substrate.A diffusion-reaction model was developed and numerically solved to describe the reaction,with results confirming the presence of mass transfer limitations in the early stages of hydrolysis.The stability of the immobilized enzyme was demonstrated by retaining over 90%of its initial activity after being stored at 4℃ for 70 days.Furthermore,the immobilized A@ZIF-L was used to hy-drolyze protein extracts derived from Scenedesmus sp.microalgae.The bioactivity of the resulting protein hy-drolysates was characterized,showing a total phenolic content of 29.1±0.6 mg GAE g^(-1)and a radical scavenging activity of 82.75±2.20%.These findings highlight the potential of Alcalase-based biocatalysts for applications in the food industry.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52104371 and U21A20116)the Liaoning Province Science and Technology Plan Project(No.2022-MS-109)the State Key Laboratory of Solidification Processing in NWPU(Grant No SKLSP202311).
文摘Ultra-high strength steels with a strength level of 2000 MPa are critical structural materials for some extreme service environments but face problems of low ductility and bad toughness.Current research effort s often focus on improving individual property,such as elongation or toughness.Therefore,it re-mains a significant challenge to unify both features of high strength,high ductility,and high toughness in one material.Adding precious metals such as Ni and Co and using aging treatment can achieve good strength and ductility in the maraging steels,but the cost is too high.In this study,we report a lean 2.4 GPa ultra-high-strength steel with a uniform elongation of 7.7%and a V-notched impact toughness of 29 J/cm^(2),which shows a competitive advantage compared with existing aircraft landing gear steels.The alloy composition design of“Mn+microalloying”and simple possessing route of quenching,deep cryo-genic treatment,and low-temperature annealing(Q-D-L)are used to achieve low-cost preparation.The transformation behaviors and mechanisms of strengthening,ductilizing,and toughening are discussed.The developed steel possesses a fine banded-equiaxed heterogeneous original austenite structure,where the CP4 occupies most of the equiaxed austenite,with more high-angle grain boundaries,and the marten-sitic variant of the banded structure is selectively weakened,resulting in a more uniform deformation,so that the crack nucleation energy and propagation energy can be simultaneously improved.Besides,the low aspect ratio structure originating from the fine parent austenite is beneficial to stimulating out-of-lath plane and in-lath plane multiple slip systems,compared with the coarse martensite with geometric lath constraints,thus increasing the deformation capability of martensite.Consequently,with the yield strength of the sample increased to 1960 MPa,the uniform elongation remained as high as 7.7%,indi-cating a notable improvement in both strength and ductility compared to samples with coarse banded austenite structures(1718 MPa&7.6%).This study provides new insights into alloy design and processing strategies for the synergistic enhancement of multiple properties in ultra-high-strength steels.
文摘Immobilization of alcalase on a ZIF-L(A@ZIF-L)support was explored for its potential application in producing hydrolysates of proteins extracted from microalgae.The immobilized enzyme was characterized using FTIR,XRD,SEM,and TGA,and the maximum adsorption capacity was found to be 672.1±5.5 mg g^(-1)at 40℃.Adsorption equilibrium data indicated that alcalase physically adsorbed onto the ZIF-L,with the isotherm well described by the Freundlich model.The adsorption kinetics aligned best with the pseudo-first order model,suggesting that both film and intraparticle diffusion were significant.The hydrolytic activity of the immobilized A@ZIF-L was initially tested using BSA as a substrate.A diffusion-reaction model was developed and numerically solved to describe the reaction,with results confirming the presence of mass transfer limitations in the early stages of hydrolysis.The stability of the immobilized enzyme was demonstrated by retaining over 90%of its initial activity after being stored at 4℃ for 70 days.Furthermore,the immobilized A@ZIF-L was used to hy-drolyze protein extracts derived from Scenedesmus sp.microalgae.The bioactivity of the resulting protein hy-drolysates was characterized,showing a total phenolic content of 29.1±0.6 mg GAE g^(-1)and a radical scavenging activity of 82.75±2.20%.These findings highlight the potential of Alcalase-based biocatalysts for applications in the food industry.
