To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by ...To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.展开更多
Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility a...Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.展开更多
A homogenization treatment(1250 °C + 12 h) was carried out to minimize the micro-segregation of bulk 718H martensitic mold steel, as verified by advanced experimental characterization and kinetic model of diffusi...A homogenization treatment(1250 °C + 12 h) was carried out to minimize the micro-segregation of bulk 718H martensitic mold steel, as verified by advanced experimental characterization and kinetic model of diffusion. However, new research found that there are still limitations in the use of the homogenization process. The result indicates that the chemical heterogeneity can be significantly reduced after homogenization. The segregation ratio of Cr and Mo elements of sample decreased by 40.9% and 35.6% of the original level, respectively. Simultaneously, the test steel with higher strength and toughness is produced by controlling micro-segregation tempered from 540 °C to 650 °C. Importantly, it reveals that the impact energy is increased by up to 27.3%. The isotropy of impact energy in different directions can reach 0.89,resulting in an overall improvement in the isotropy. Toughness mainly depends on the orientation relationship between the crack propagation direction and the band segregation region. The chain carbides formed due to the decomposition of the micro-segregated region during tempering are considered the main source of cracks. The more evenly distributed the subsequent tempered carbides after homogenization, resulting in an increase in toughness. However, an abnormal phenomenon is found in which the yield strength after homogenization is lower than that of the untreated sample tempered at 700 °C. This result can be attributed to the combined influences of precipitation strengthening and fine grain strengthening by analyzing various strengthening mechanisms. The mutually restrictive strengthening effect leads to the limitations of the homogenization process of bulk martensitic mold steel.展开更多
By using double glow plasma surface metallurgy technique, the molybdenum （Mo） surface- modified layer on titanium （Ti） was obtained. The corresponding cross-section morphology, phase formation, and element concent...By using double glow plasma surface metallurgy technique, the molybdenum （Mo） surface- modified layer on titanium （Ti） was obtained. The corresponding cross-section morphology, phase formation, and element concentration were investigated by optical microscopy, X-ray diffraction （XRD）, and glow discharge optical emission spectroscopy （GDOES）, respectively. The experimental results indicate that the Mo modified layer is composed of a 1.7 μm pure Mo deposition layer and a 14.3μm Mo diffusion layer. Along the sample thickness direction, nanoindentation tests were performed on the cross-section of the Mo diffusion layer and the Ti substrate （for the comparison purpose） by Hysitron TI900 TriboIndenter. The 2D and 3D residual indentation profiles of the Mo diffusion layer were obtained by scanning probe microscopy （SPM）. The elastic modulus and hardness values of every indent were acquired and analyzed. According to the load-displacement curves, the plastic deformation degrees of the Mo diffusion layer and the Ti substrate were analyzed. It is indicated that the Mo diffusion layer possesses high strength-toughness.展开更多
Systematic research on developing a series of extra high strength steel plates for shipbuilding via thermomechanical control process(TMCP)is introduced.A microalloyed low carbon-equivalent SiMnCrNiCu steel was used to...Systematic research on developing a series of extra high strength steel plates for shipbuilding via thermomechanical control process(TMCP)is introduced.A microalloyed low carbon-equivalent SiMnCrNiCu steel was used to develop F460 steel.Ultra low carbon Cu-Ni containing steels were used to develop NV-F550,NV-F620 and NV-F690 steel plates.The effect of TMCP parameters on microstructure and properties was investigated by test-scale plant trials.Industrial production trials were conducted to verify the validity of the laboratory studies on the F460 steel.Heavy plates in 45-60 mm thickness met Det Norske Veritas NV-F460 specification.The effect of heat-input on the mechanical properties of the coarse-grained-heat-affect-zone(CGHAZ)of the advanced heavy plates was studied.展开更多
The second phase in multi-phase alloys has connection with many important phenomena such as aging strengthening,dispersion strengthening,secondary hardening,crystal refinement.In this paper,the interface conjunction f...The second phase in multi-phase alloys has connection with many important phenomena such as aging strengthening,dispersion strengthening,secondary hardening,crystal refinement.In this paper,the interface conjunction factors of the interface between MC(M=V,Nb,Ti) and austenite and martensite are calculate out.The relationship between these factors and the characteristics are analyzed.The reason for the second phases being fine and dispersing and their strengthening and toughening effect on the alloy is explained using the relationship.Based on the relationship,the valence electron structure of the interface between the second phase particles and the matrix can be optimized by changing the alloying elements,which make it possible to design the composition of alloys from the valence electron structure of the second phase particles.展开更多
基金supported by Specific Research Project of Guangxi for Research Bases and Talents(Grant No.GuiKe AD19245145)Natural Science Foundation of Guangxi Province(Grant No.2018GXNSFBA281106).
文摘To improve the strength-toughness of 13Cr4NiMo martensitic stainless steel(13-4MSS),a thermal cyclic heat treatment(TCHT)combined with the advantage of tempering was proposed.The microstructures were characterized by scanning electron microscopy,X-ray diffraction and electron backscattered diffraction,and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution.It was found that grains and the martensitic matrix were refined by TCHT through the cyclic quenching transformation and austenite recrystallization,which was conducive to more nucleation quantity of reversed austenite during tempering.Two-sphericalcap nucleation model was used to explain the effect of refined grains of TCHT on the nucleation of reversed austenite.Grain refinement by TCHT improved the brittle fracture stress to reduce the ductile-brittle transition temperature and thus improved the cryogenic impact toughness of 13-4MSS.Reversed austenite distributed at the martensitic lath boundary enhances the crack arrest performance and increases the britle fracture stress.It is concluded that reasonable TCHT plus tempering process significantly improves the strength-toughness of 13-4MSS,reflecting the comprehensive effect of grain refinement and reversed austenite.
基金supported by the National Natural Science Foundation of China(Nos.52271113,92163201)Jinyu Zhang is grateful for the Shaanxi Province Youth Innovation Team(No.22JP042)Shaanxi Province Innovation Team Project(2024RS-CXTD-58).
文摘Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.
基金The work was financially supported by the China Postdoctoral Science Foundation(No.2019M661153)The authors also appreciate the financial support by Young Talent Project by Shenyang National Laboratory for Materials Science(No.2020000358)+2 种基金Doctoral Research Startup Fund Guidance Program Project of Liaoning Province(No.2020-BS-004)Project to Strengthen Industrial Development at the Grass-roots Level(No.TC190A4DA/35)Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110886).
文摘A homogenization treatment(1250 °C + 12 h) was carried out to minimize the micro-segregation of bulk 718H martensitic mold steel, as verified by advanced experimental characterization and kinetic model of diffusion. However, new research found that there are still limitations in the use of the homogenization process. The result indicates that the chemical heterogeneity can be significantly reduced after homogenization. The segregation ratio of Cr and Mo elements of sample decreased by 40.9% and 35.6% of the original level, respectively. Simultaneously, the test steel with higher strength and toughness is produced by controlling micro-segregation tempered from 540 °C to 650 °C. Importantly, it reveals that the impact energy is increased by up to 27.3%. The isotropy of impact energy in different directions can reach 0.89,resulting in an overall improvement in the isotropy. Toughness mainly depends on the orientation relationship between the crack propagation direction and the band segregation region. The chain carbides formed due to the decomposition of the micro-segregated region during tempering are considered the main source of cracks. The more evenly distributed the subsequent tempered carbides after homogenization, resulting in an increase in toughness. However, an abnormal phenomenon is found in which the yield strength after homogenization is lower than that of the untreated sample tempered at 700 °C. This result can be attributed to the combined influences of precipitation strengthening and fine grain strengthening by analyzing various strengthening mechanisms. The mutually restrictive strengthening effect leads to the limitations of the homogenization process of bulk martensitic mold steel.
基金Funded by the National Natural Science Foundation of China(No.51171125)the Shanxi Province Science and Technology Key Project(No.20110321051)the Reasearch Project Supported by Shanxi Province Foundation for Returned Overseas Scholars(2011-038)
文摘By using double glow plasma surface metallurgy technique, the molybdenum （Mo） surface- modified layer on titanium （Ti） was obtained. The corresponding cross-section morphology, phase formation, and element concentration were investigated by optical microscopy, X-ray diffraction （XRD）, and glow discharge optical emission spectroscopy （GDOES）, respectively. The experimental results indicate that the Mo modified layer is composed of a 1.7 μm pure Mo deposition layer and a 14.3μm Mo diffusion layer. Along the sample thickness direction, nanoindentation tests were performed on the cross-section of the Mo diffusion layer and the Ti substrate （for the comparison purpose） by Hysitron TI900 TriboIndenter. The 2D and 3D residual indentation profiles of the Mo diffusion layer were obtained by scanning probe microscopy （SPM）. The elastic modulus and hardness values of every indent were acquired and analyzed. According to the load-displacement curves, the plastic deformation degrees of the Mo diffusion layer and the Ti substrate were analyzed. It is indicated that the Mo diffusion layer possesses high strength-toughness.
文摘Systematic research on developing a series of extra high strength steel plates for shipbuilding via thermomechanical control process(TMCP)is introduced.A microalloyed low carbon-equivalent SiMnCrNiCu steel was used to develop F460 steel.Ultra low carbon Cu-Ni containing steels were used to develop NV-F550,NV-F620 and NV-F690 steel plates.The effect of TMCP parameters on microstructure and properties was investigated by test-scale plant trials.Industrial production trials were conducted to verify the validity of the laboratory studies on the F460 steel.Heavy plates in 45-60 mm thickness met Det Norske Veritas NV-F460 specification.The effect of heat-input on the mechanical properties of the coarse-grained-heat-affect-zone(CGHAZ)of the advanced heavy plates was studied.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59631060) .
文摘The second phase in multi-phase alloys has connection with many important phenomena such as aging strengthening,dispersion strengthening,secondary hardening,crystal refinement.In this paper,the interface conjunction factors of the interface between MC(M=V,Nb,Ti) and austenite and martensite are calculate out.The relationship between these factors and the characteristics are analyzed.The reason for the second phases being fine and dispersing and their strengthening and toughening effect on the alloy is explained using the relationship.Based on the relationship,the valence electron structure of the interface between the second phase particles and the matrix can be optimized by changing the alloying elements,which make it possible to design the composition of alloys from the valence electron structure of the second phase particles.
