The effect of micro-void on transverse stiffness and strength for fiber-reinforced composites subjected to load perpendicular to fiber is studied using the state-based peridynamic(PD)theory.The heterogeneous microstru...The effect of micro-void on transverse stiffness and strength for fiber-reinforced composites subjected to load perpendicular to fiber is studied using the state-based peridynamic(PD)theory.The heterogeneous microstructure with micro-voids are discretized with irregular and non-uniform grids on mesoscale.The PD representative volume element with randomly distributed and sized micro-voids has been established with periodic boundary conditions.A parametric study was performed to evaluate the effects of void fraction and void size on transverse properties.It was found that the transverse modulus decreases with the void fraction in the range of 0.5–2%.A smaller void has a greater impact on the transverse modulus than a larger void under the same void content.The crack growth path for the multi-fiber model subjected to transverse tension was analyzed.The PD predictions show that cracks initiate at the interface between fiber and matrix,then deflect to the micro-voids nearby.The PD predictions match well with the analytical and experimental observations available in the literature.展开更多
Although fine equiaxed structure benefits both strength and ductility in titanium alloys,it is often considered incompatible with high toughness,for its insufficient ability to deflect propagating cracks compared to c...Although fine equiaxed structure benefits both strength and ductility in titanium alloys,it is often considered incompatible with high toughness,for its insufficient ability to deflect propagating cracks compared to coarse lamellar structure.This work reports an excellent combination of standard Charpy impact toughness(∼100 J)and yield strength(∼820 MPa)in a powder metallurgy titanium alloy with fine equiaxed structure(∼1.5μm),wherein the β matrix exists as equiaxed nodules and fine ligaments for globularization of α grains.The impact curve divided with the“compliance changing rate”(CCR)method indicates that the energy consumed by crack propagation is dominant(∼82%)during the impact process.Fractographic and structural examinations indicate that multiple micro-voids nucleation near boundaries between fine β ligaments and α grains mitigates local stress concentration,and that coordinated deformation between equiaxed β nodules and α grains hinders crack propagation,which together enable the excellent combination of yield strength and impact toughness.Our work provides a new pathway for designing impact-resistant titanium alloys.展开更多
C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl com...C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.11902197 and 11972234is sponsored by Shanghai Sailing Program under Contract No.19YF1421700.
文摘The effect of micro-void on transverse stiffness and strength for fiber-reinforced composites subjected to load perpendicular to fiber is studied using the state-based peridynamic(PD)theory.The heterogeneous microstructure with micro-voids are discretized with irregular and non-uniform grids on mesoscale.The PD representative volume element with randomly distributed and sized micro-voids has been established with periodic boundary conditions.A parametric study was performed to evaluate the effects of void fraction and void size on transverse properties.It was found that the transverse modulus decreases with the void fraction in the range of 0.5–2%.A smaller void has a greater impact on the transverse modulus than a larger void under the same void content.The crack growth path for the multi-fiber model subjected to transverse tension was analyzed.The PD predictions show that cracks initiate at the interface between fiber and matrix,then deflect to the micro-voids nearby.The PD predictions match well with the analytical and experimental observations available in the literature.
基金financially supported by the National Natural Science Foundation of China(No.52371156).
文摘Although fine equiaxed structure benefits both strength and ductility in titanium alloys,it is often considered incompatible with high toughness,for its insufficient ability to deflect propagating cracks compared to coarse lamellar structure.This work reports an excellent combination of standard Charpy impact toughness(∼100 J)and yield strength(∼820 MPa)in a powder metallurgy titanium alloy with fine equiaxed structure(∼1.5μm),wherein the β matrix exists as equiaxed nodules and fine ligaments for globularization of α grains.The impact curve divided with the“compliance changing rate”(CCR)method indicates that the energy consumed by crack propagation is dominant(∼82%)during the impact process.Fractographic and structural examinations indicate that multiple micro-voids nucleation near boundaries between fine β ligaments and α grains mitigates local stress concentration,and that coordinated deformation between equiaxed β nodules and α grains hinders crack propagation,which together enable the excellent combination of yield strength and impact toughness.Our work provides a new pathway for designing impact-resistant titanium alloys.
基金Projects(51201134,51271147)supported by the National Natural Science Foundation of ChinaProject(2015JM5181)supported by the Natural Science Foundation of Shaanxi Province,China+1 种基金Project(115-QP-2014)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),ChinaProject(3102014JCQ01023)supported by the Fundamental Research Funds for the Central Universities,China
文摘C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.
