The independent influence of microstructural features on fracture toughness of TC21alloy with lamellar microstructure was investigated.Triple heat treatments were designed to obtain lamellar microstructures with diffe...The independent influence of microstructural features on fracture toughness of TC21alloy with lamellar microstructure was investigated.Triple heat treatments were designed to obtain lamellar microstructures with different parameters,which were characterized by OM and SEM.The size and content ofαplates were mainly determined by cooling rate from singleβphase field and solution temperature in two-phase field;while the precipitation behavior of secondaryαplatelets was dominantly controlled by aging temperature in two-phase field.The content and thickness ofαplates and the thickness of secondaryαplatelets were important microstructural features influencing the fracture toughness.Both increasing the content ofαplates and thickeningαplates(or secondaryαplatelets)could enhance the fracture toughness of TC21alloy.Based on energy consumption by the plastic zone of crack tip inαplates,a toughening mechanism for titanium alloys was proposed.展开更多
The clay mineral content of Daqing Gulong shale is in the range of about 35%–45%,with particle sizes less than 0.0039 mm.The horizontal fluidity of oil in Gulong shale is poor,with near-zero vertical flowability.As a...The clay mineral content of Daqing Gulong shale is in the range of about 35%–45%,with particle sizes less than 0.0039 mm.The horizontal fluidity of oil in Gulong shale is poor,with near-zero vertical flowability.As a result,Gulong shale has been considered to lack commercial value.In recent years,however,interdisciplinary research in geoscience,percolation mechanics,thermodynamics,and surface mechanics has demonstrated that Gulong shale oil has a high degree of maturity and a high residual hydrocarbon content.The expulsion efficiency of Gulong shale in the high mature stage is 32%–48%.Favorable storage spaces in Gulong shale include connecting pores and lamellar fractures developed between and within organic matter and clay mineral complexes.The shale oil mainly occurs in micro-and nano-pores,bedding fractures,and lamellar fractures,with a high gas–oil ratio and medium–high movable oil saturation.Gulong shale has the characteristics of high hardness,a high elastic modulus,and high fracture toughness.This study achieves breakthroughs in the exploration and development of Gulong shale,including the theories of hydrocarbon generation and accumulation,the technologies of mobility and fracturing,and recoverability.It confirms the major transition of Gulong shale from oil generation to oil production,which has extremely significant scientific value and application potential for China’s petroleum industry.展开更多
The fracture behavior of fully lamellar γ-TiAl alloys depends on the angle between the lamellar orientation and loading axis,but the role of the presentation of grain boundary cannot be ignored.To investigate the inf...The fracture behavior of fully lamellar γ-TiAl alloys depends on the angle between the lamellar orientation and loading axis,but the role of the presentation of grain boundary cannot be ignored.To investigate the influence of the grain boundary on the initiation and propagation of cracks,the tensile test of the alloy was conducted at room temperature with loading axis parallel and perpendicular to the lamellar orientation,respectively.The cracks adjacent to the fracture zone of the tensile specimens have been investigated to analyze the fracture behavior.Results show that the grain boundary has dual influences on the fracture behavior.When the loading axis is parallel to the lamellar orientation,cracks are preferentially initiated at and propagate along the grain boundaries.When the loading axis is perpendicular to the lamellar orientation,the grain boundaries can prevent the propagation of cracks from running across.Additionally,serrated-shape grain boundaries have a better inhibiting effect on the propagation of cracks than planar boundaries.展开更多
The fracture behavior of fully lamellar binary γ-TiAI alloys is extremely anisotropic with respect to the lamellar orientation. For the fully lamellar Ti-46Al-0.5W-0.5Si alloy, the existence of silicide clusters play...The fracture behavior of fully lamellar binary γ-TiAI alloys is extremely anisotropic with respect to the lamellar orientation. For the fully lamellar Ti-46Al-0.5W-0.5Si alloy, the existence of silicide clusters plays a critical role on the fracture behavior. In the present study, tensile test and three point bending test were performed at room temperature with the loading axis parallel and perpendicular to the lamellar orientation, respectively. To investigate the influence of silicide clusters on the initiation and propagation of cracks, the fracture surface and the cracks adjacent to the fracture zone of the specimens have been analyzed. Results show that the fracture process is related to the morphology and distribution of the silicide clusters. Crack preferentially initiates at and propagates along the interface of silicide and a2/7 lamellar with the loading axis perpendicular to the length direction of silicide. While the silicide can prevent the propagation of cracks from running across with the crack growth direction perpendicular to the length direction of silicide.展开更多
The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile ...The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile and compressive tests were examined in a scanning electron microscope (SEM). The in situ tensile testing was further carried out in a SEM and the crack growth path of samples was observed. The result shows that there is a remarkable effect of lamellar structure of CSD TiAl alloy on its deformation and fracture process. Especially, the main crack extension is dependent on the lamellar direction relative to tensile loading axis. SEM observations indicate that there is a shielding toughening effect of lamellar structure on fracture in CSD samples, such as, crack deflection, crack path tortuousity, and crack branching, etc. Moreover, the crack growth path shows that the main crack grows tortuously and uncontinuously by ligaments bridging many microcracks in front of crack tip. The effect mechanism of microstructure on deformation and fracture process is discussed.[展开更多
We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both ...We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both the inplane(parallel to the nano-lamellae)and out-of-plane(normal and 45inclined to the nano-lamellae)mechanical anisotropy.The parallel orientation demonstrates the greatest tensile strength while the inclined orientation exhibits the least strength.The tensile tests in normal and inclined directions also indicate significant transient elastic-plastic response due to the strain path change.Fractographic examination demonstrates that the specimen fails in the normal direction by premature micro-void nucleation and growth,which restricts its tensile strength;however,we identified zig-zag cracking associated with lamellar shear cracking in the inclined direction.展开更多
文摘The independent influence of microstructural features on fracture toughness of TC21alloy with lamellar microstructure was investigated.Triple heat treatments were designed to obtain lamellar microstructures with different parameters,which were characterized by OM and SEM.The size and content ofαplates were mainly determined by cooling rate from singleβphase field and solution temperature in two-phase field;while the precipitation behavior of secondaryαplatelets was dominantly controlled by aging temperature in two-phase field.The content and thickness ofαplates and the thickness of secondaryαplatelets were important microstructural features influencing the fracture toughness.Both increasing the content ofαplates and thickeningαplates(or secondaryαplatelets)could enhance the fracture toughness of TC21alloy.Based on energy consumption by the plastic zone of crack tip inαplates,a toughening mechanism for titanium alloys was proposed.
基金supported by the National Natural Science Foundation of China(72088101 and 42090025)the China National Petroleum Corporation(2019E-26 and YGJ2020-3)。
文摘The clay mineral content of Daqing Gulong shale is in the range of about 35%–45%,with particle sizes less than 0.0039 mm.The horizontal fluidity of oil in Gulong shale is poor,with near-zero vertical flowability.As a result,Gulong shale has been considered to lack commercial value.In recent years,however,interdisciplinary research in geoscience,percolation mechanics,thermodynamics,and surface mechanics has demonstrated that Gulong shale oil has a high degree of maturity and a high residual hydrocarbon content.The expulsion efficiency of Gulong shale in the high mature stage is 32%–48%.Favorable storage spaces in Gulong shale include connecting pores and lamellar fractures developed between and within organic matter and clay mineral complexes.The shale oil mainly occurs in micro-and nano-pores,bedding fractures,and lamellar fractures,with a high gas–oil ratio and medium–high movable oil saturation.Gulong shale has the characteristics of high hardness,a high elastic modulus,and high fracture toughness.This study achieves breakthroughs in the exploration and development of Gulong shale,including the theories of hydrocarbon generation and accumulation,the technologies of mobility and fracturing,and recoverability.It confirms the major transition of Gulong shale from oil generation to oil production,which has extremely significant scientific value and application potential for China’s petroleum industry.
基金financially supported by the National Natural Science Foundation of China (50975060,50901025)the National Basic Research Program of China (2011CB610406)+2 种基金the China Postdoctoral Science Foundation (201104420,20090450840)the Fundamental Research Funds for the Central Universities (HIT.BRET1.2010008)the Scientific and Technological Project in Heilongjiang Province (GZ09A206)
文摘The fracture behavior of fully lamellar γ-TiAl alloys depends on the angle between the lamellar orientation and loading axis,but the role of the presentation of grain boundary cannot be ignored.To investigate the influence of the grain boundary on the initiation and propagation of cracks,the tensile test of the alloy was conducted at room temperature with loading axis parallel and perpendicular to the lamellar orientation,respectively.The cracks adjacent to the fracture zone of the tensile specimens have been investigated to analyze the fracture behavior.Results show that the grain boundary has dual influences on the fracture behavior.When the loading axis is parallel to the lamellar orientation,cracks are preferentially initiated at and propagate along the grain boundaries.When the loading axis is perpendicular to the lamellar orientation,the grain boundaries can prevent the propagation of cracks from running across.Additionally,serrated-shape grain boundaries have a better inhibiting effect on the propagation of cracks than planar boundaries.
基金supported by National Natural Science Foundation of China(Grant Nos.50975060,50901025)the National Basic Research Program of China(Grant No.2011CB610406)+2 种基金the China Postdoctoral Science Foundation(Grant Nos.201104420,20090450840)the Fundamental Research Funds for the Central Universities(Grant No.HIT.BRET1.2010008)Scientific and Technological Project in Heilongjiang Province(Grant No.GZ09A206)
文摘The fracture behavior of fully lamellar binary γ-TiAI alloys is extremely anisotropic with respect to the lamellar orientation. For the fully lamellar Ti-46Al-0.5W-0.5Si alloy, the existence of silicide clusters plays a critical role on the fracture behavior. In the present study, tensile test and three point bending test were performed at room temperature with the loading axis parallel and perpendicular to the lamellar orientation, respectively. To investigate the influence of silicide clusters on the initiation and propagation of cracks, the fracture surface and the cracks adjacent to the fracture zone of the specimens have been analyzed. Results show that the fracture process is related to the morphology and distribution of the silicide clusters. Crack preferentially initiates at and propagates along the interface of silicide and a2/7 lamellar with the loading axis perpendicular to the length direction of silicide. While the silicide can prevent the propagation of cracks from running across with the crack growth direction perpendicular to the length direction of silicide.
基金Project (E990 0 0 7)supportedbyFujianProvincialNaturalScienceFoundation P .R .China
文摘The effects of lamellar structure on deformation and fracture behavior in a Ti 48Al 2Mn 2Nb alloy produced by centrifugal spray deposition(CSD) were investigated. The deformation and fracture of samples after tensile and compressive tests were examined in a scanning electron microscope (SEM). The in situ tensile testing was further carried out in a SEM and the crack growth path of samples was observed. The result shows that there is a remarkable effect of lamellar structure of CSD TiAl alloy on its deformation and fracture process. Especially, the main crack extension is dependent on the lamellar direction relative to tensile loading axis. SEM observations indicate that there is a shielding toughening effect of lamellar structure on fracture in CSD samples, such as, crack deflection, crack path tortuousity, and crack branching, etc. Moreover, the crack growth path shows that the main crack grows tortuously and uncontinuously by ligaments bridging many microcracks in front of crack tip. The effect mechanism of microstructure on deformation and fracture process is discussed.[
基金financial support from the National Key R&D Program of China(Grant No.2017YFA0204403)financial support by the National Natural Science Foundation of China(Grant No.51931010,51601196 and U1608257)+2 种基金the Liaoning Revitalization Talents Program(Grant No.XLYC1802026)the Key Research Program of Frontier Science,Chinese Academy of Sciencesthe financial support of the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX180408).
文摘We produced a 316 L stainless steel with heterogeneous nanometer-thick lamellar structures by severe cold-rolling at room temperature,and conducted micro-scale tensile tests in different orientations to evaluate both the inplane(parallel to the nano-lamellae)and out-of-plane(normal and 45inclined to the nano-lamellae)mechanical anisotropy.The parallel orientation demonstrates the greatest tensile strength while the inclined orientation exhibits the least strength.The tensile tests in normal and inclined directions also indicate significant transient elastic-plastic response due to the strain path change.Fractographic examination demonstrates that the specimen fails in the normal direction by premature micro-void nucleation and growth,which restricts its tensile strength;however,we identified zig-zag cracking associated with lamellar shear cracking in the inclined direction.
