Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical p...Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates(DPNLs)with different layer thicknesses are investigated using molecular dynamics simulations.The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible,while it affects the plastic deformation mechanism of amorphous layers distinctly.The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs,which is inversely proportional to the layer thickness.It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat.Young's moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces.Furthermore,the main plastic deformation mechanism in crystalline part:grain reorientation,transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti,has also been displayed in the present work.The results may provide a guideline for design of high-performance Ti and its alloy.展开更多
Simulation of molecular dynamics using Embedded Atom Method(EAM) potentials is performed to investigate the mechanical properties of single crystal Al along various crystallographic orientations under tensile loading....Simulation of molecular dynamics using Embedded Atom Method(EAM) potentials is performed to investigate the mechanical properties of single crystal Al along various crystallographic orientations under tensile loading.The specimens are provided with one or two embedded circular voids to analyze the damage evolution by void growth and coalescence.The simulation result shows that the Young's modulus,yielding stress and ultimate stress decrease with the emergence of the voids.Besides,the simulations show that the single-crystal Al in different crystallographic orientations behaves differently in elongation deformations.The single-crystal Al with 100 crystallographic orientations has greater ductility than other orientated specimens.The incipient plastic deformation and the stress-strain curves are presented and discussed for further understanding of the mechanical properties of single-crystal Al.展开更多
Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directi...Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directions are utilized to systematically study the mechanical performance of the cracked material.The results indicate that pre-existing crack dramatically changes the plastic deformation mechanism of the Ti/Ni nanolaminate.Unlike the initial plastic deformation originating from the interface or weak Ti layer of the crack-free samples,the plastic behavior of cracked Ti/Ni nanolaminate first occurs at the crack tip due to the local stress concentration.Subsequent plastic deformation is dominated by the interaction between the crack and interface.The Ti/Ni interface not only impedes the movement of the initial plastic deformation carriers(dislocation,slip band,and deformation twinning)from the crack tip,but also promotes the movement of interfacial dislocations in the tension process.Microstructure evolution analysis further confirms that the plastic deformation mechanism transition is ascribed to the orientation-dependent tensile behavior at the crack tip,which is intrinsically attributed to the anisotropy of the certain crystal structure and loading direction of the cracked Ti/Ni nanolaminate.In addition,by analyzing the effects of different plastic deformation carriers on crack propagation in specific crystal,it can be discovered that the interfacial dislocations moving towards the crack tip can further promote the crack growth.展开更多
The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield streng...The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield strength of nanotwinned Al decreases with the increase of twin spacing,which is related to the repulsive force between twin boundary and the dislocation.The result also shows that there is no strain-hardening at the yield point.On the contrary,the stress is raised by strain hardening in the plastic stage.In addition,we also investigate the effects of stacking fault thickness and temperature on the yield strength of the Al nanowire.The simulation results indicate that the stacking fault may strengthen the Al nanowire when the thickness of the stacking fault is below a critical value.展开更多
The dual-phase amorphous/crystalline nanostructured model proves to be an effective method to improve the plasticity of Mg alloys.The purpose of this paper is to explore an approach to improving the ductility and stre...The dual-phase amorphous/crystalline nanostructured model proves to be an effective method to improve the plasticity of Mg alloys.The purpose of this paper is to explore an approach to improving the ductility and strength of Mg alloys at the same time.Here,the effect of amorphous phase strength,crystalline phase strength,and amorphous boundary(AB)spacing on the mechanical properties of dual-phase Mg alloys(DPMAs)under tensile loading are investigated by the molecular dynamics simulation method.The results confirm that the strength of DPMA can be significantly improved while its excellent plasticity is maintained by adjusting the strength of the amorphous phase or crystalline phase and optimizing the AB spacing.For the DPMA,when the amorphous phase(or crystalline phase)is strengthened to enhance its strength,the AB spacing should be increased(or reduced)to obtain superior plasticity at the same time.The results also indicate that the DPMA containing high strength amorphous phase exhibits three different deformation modes during plastic deformation with the increase of AB spacing.The research results will present a theoretical basis and early guidance for designing and developing the high-performance dual-phase hexagonal close-packed nanostructured metals.展开更多
Using molecular dynamics simulations,the plastic deformation behavior of nanocrytalline Ti has been investigated under tension and compression normal to the{0001},{1010},and{1210}planes.The results indicate that the p...Using molecular dynamics simulations,the plastic deformation behavior of nanocrytalline Ti has been investigated under tension and compression normal to the{0001},{1010},and{1210}planes.The results indicate that the plastic deformation strongly depends on crystal orientation and loading directions.Under tension normal to basal plane,the deformation mechanism is mainly the grain reorientation and the subsequent deformation twinning.Under compression,the transformation of hexagonal-close packed(HCP)-Ti to face-centered cubic(FCC)-Ti dominates the deformation.When loading is normal to the prismatic planes(both{1010}and{1210}),the deformation mechanism is primarily the phase transformation among HCP,body-centered cubic(BCC),and FCC structures,regardless of loading mode.The orientation relations(OR)of{0001}HCP||{111}FCC and<1210>HCP||<110>FCC,and{1010}HCP||{110}FCC and<0001>HCP||<010>FCC between the HCP and FCC phases have been observed in the present work.For the transformation of HCP→BCC→HCP,the OR is{0001}α1||{110}β||{1010}α2(HCP phase before the critical strain is defined as α1-Ti,BCC phase is defined as β-Ti,and the HCP phase after the critical strain is defined as α2-Ti).Energy evolution during the various loading processes further shows the plastic anisotropy of nanocrystalline Ti is determined by the stacking order of the atoms.The results in the present work will promote the in-depth study of the plastic deformation mechanism of HCP materials.展开更多
Novel properties and applications of multilayered nanowires(MNWs)urge researchers to understand their mechanical behaviors comprehensively.Using the molecular dynamic simulation,tensile behaviors of Ti/Ni MNWs are inv...Novel properties and applications of multilayered nanowires(MNWs)urge researchers to understand their mechanical behaviors comprehensively.Using the molecular dynamic simulation,tensile behaviors of Ti/Ni MNWs are investigated under a series of layer thickness values(1.31,2.34,and 7.17 nm)and strain rates(1.0×10^(8)s^(-1)≤ε≤5.0×10^(10)s^(-1)).The results demonstrate that deformation mechanisms of isopachous Ti/Ni MNWs are determined by the layer thickness and strain rate.Four distinct strain rate regions in the tensile process can be discovered,which are small,intermediate,critical,and large strain rate regions.As the strain rate increases,the initial plastic behaviors transform from interface shear(the shortest sample)and grain reorientation(the longest sample)in small strain rate region to amorphization of crystalline structures(all samples)in large strain rate region.Microstructure evolutions reveal that the disparate tensile behaviors are ascribed to the atomic fractions of different structures in small strain rate region,and only related to collapse of crystalline atoms in high strain rate region.A layer thickness-strain rate-dependent mechanism diagram is given to illustrate the couple effect on the plastic deformation mechanisms of the isopachous nanowires.The results also indicate that the modulation ratio significantly affects the tensile properties of unequal Ti/Ni MNWs,but barely affect the plastic deformation mechanisms of the materials.The observations from this work will promote theoretical researches and practical applications of Ti/Ni MNWs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51902254 and 12072286)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2021JZ-53 and 2018JQ5108)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.20JK0845)。
文摘Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates(DPNLs)with different layer thicknesses are investigated using molecular dynamics simulations.The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible,while it affects the plastic deformation mechanism of amorphous layers distinctly.The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs,which is inversely proportional to the layer thickness.It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat.Young's moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces.Furthermore,the main plastic deformation mechanism in crystalline part:grain reorientation,transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti,has also been displayed in the present work.The results may provide a guideline for design of high-performance Ti and its alloy.
基金Supported by the National Science Foundation of China under Grant No.11572259
文摘Simulation of molecular dynamics using Embedded Atom Method(EAM) potentials is performed to investigate the mechanical properties of single crystal Al along various crystallographic orientations under tensile loading.The specimens are provided with one or two embedded circular voids to analyze the damage evolution by void growth and coalescence.The simulation result shows that the Young's modulus,yielding stress and ultimate stress decrease with the emergence of the voids.Besides,the simulations show that the single-crystal Al in different crystallographic orientations behaves differently in elongation deformations.The single-crystal Al with 100 crystallographic orientations has greater ductility than other orientated specimens.The incipient plastic deformation and the stress-strain curves are presented and discussed for further understanding of the mechanical properties of single-crystal Al.
基金Project supported by the National Natural Science Foundation of China(Grant No.11572259)the Program for International Cooperation and Exchanges of Shaanxi Province,China(Grant No.2016KW-049)+1 种基金the Natural Science Foundation of Shaanxi Province,China(Grant No.2019JQ-827)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.19JK0672).
文摘Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directions are utilized to systematically study the mechanical performance of the cracked material.The results indicate that pre-existing crack dramatically changes the plastic deformation mechanism of the Ti/Ni nanolaminate.Unlike the initial plastic deformation originating from the interface or weak Ti layer of the crack-free samples,the plastic behavior of cracked Ti/Ni nanolaminate first occurs at the crack tip due to the local stress concentration.Subsequent plastic deformation is dominated by the interaction between the crack and interface.The Ti/Ni interface not only impedes the movement of the initial plastic deformation carriers(dislocation,slip band,and deformation twinning)from the crack tip,but also promotes the movement of interfacial dislocations in the tension process.Microstructure evolution analysis further confirms that the plastic deformation mechanism transition is ascribed to the orientation-dependent tensile behavior at the crack tip,which is intrinsically attributed to the anisotropy of the certain crystal structure and loading direction of the cracked Ti/Ni nanolaminate.In addition,by analyzing the effects of different plastic deformation carriers on crack propagation in specific crystal,it can be discovered that the interfacial dislocations moving towards the crack tip can further promote the crack growth.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10902083)the Program for New Scientific and Technological Star of Shaanxi Province,China (Grant No. 2012KJXX-39)
文摘The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield strength of nanotwinned Al decreases with the increase of twin spacing,which is related to the repulsive force between twin boundary and the dislocation.The result also shows that there is no strain-hardening at the yield point.On the contrary,the stress is raised by strain hardening in the plastic stage.In addition,we also investigate the effects of stacking fault thickness and temperature on the yield strength of the Al nanowire.The simulation results indicate that the stacking fault may strengthen the Al nanowire when the thickness of the stacking fault is below a critical value.
基金National Natural Science Foundation of China(Grant No.11572259)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2018JM101 and 2019JQ-827)the Program for Graduate Innovation Fund of Xi’an Shiyou University,China(Grant No.YCS19111004).
文摘The dual-phase amorphous/crystalline nanostructured model proves to be an effective method to improve the plasticity of Mg alloys.The purpose of this paper is to explore an approach to improving the ductility and strength of Mg alloys at the same time.Here,the effect of amorphous phase strength,crystalline phase strength,and amorphous boundary(AB)spacing on the mechanical properties of dual-phase Mg alloys(DPMAs)under tensile loading are investigated by the molecular dynamics simulation method.The results confirm that the strength of DPMA can be significantly improved while its excellent plasticity is maintained by adjusting the strength of the amorphous phase or crystalline phase and optimizing the AB spacing.For the DPMA,when the amorphous phase(or crystalline phase)is strengthened to enhance its strength,the AB spacing should be increased(or reduced)to obtain superior plasticity at the same time.The results also indicate that the DPMA containing high strength amorphous phase exhibits three different deformation modes during plastic deformation with the increase of AB spacing.The research results will present a theoretical basis and early guidance for designing and developing the high-performance dual-phase hexagonal close-packed nanostructured metals.
基金Project supported by the National Natural Science Foundation of China(Grant No.11572259)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2019JQ-827,2018JM1013,and 2018JQ5108)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.19JK0672)。
文摘Using molecular dynamics simulations,the plastic deformation behavior of nanocrytalline Ti has been investigated under tension and compression normal to the{0001},{1010},and{1210}planes.The results indicate that the plastic deformation strongly depends on crystal orientation and loading directions.Under tension normal to basal plane,the deformation mechanism is mainly the grain reorientation and the subsequent deformation twinning.Under compression,the transformation of hexagonal-close packed(HCP)-Ti to face-centered cubic(FCC)-Ti dominates the deformation.When loading is normal to the prismatic planes(both{1010}and{1210}),the deformation mechanism is primarily the phase transformation among HCP,body-centered cubic(BCC),and FCC structures,regardless of loading mode.The orientation relations(OR)of{0001}HCP||{111}FCC and<1210>HCP||<110>FCC,and{1010}HCP||{110}FCC and<0001>HCP||<010>FCC between the HCP and FCC phases have been observed in the present work.For the transformation of HCP→BCC→HCP,the OR is{0001}α1||{110}β||{1010}α2(HCP phase before the critical strain is defined as α1-Ti,BCC phase is defined as β-Ti,and the HCP phase after the critical strain is defined as α2-Ti).Energy evolution during the various loading processes further shows the plastic anisotropy of nanocrystalline Ti is determined by the stacking order of the atoms.The results in the present work will promote the in-depth study of the plastic deformation mechanism of HCP materials.
基金Project supported by the National Natural Science Foundation of China(Grant No.11572259)the Natural Science Foundation of Shaanxi Province,China(Grant No.2019JQ-827)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.19JK0672).
文摘Novel properties and applications of multilayered nanowires(MNWs)urge researchers to understand their mechanical behaviors comprehensively.Using the molecular dynamic simulation,tensile behaviors of Ti/Ni MNWs are investigated under a series of layer thickness values(1.31,2.34,and 7.17 nm)and strain rates(1.0×10^(8)s^(-1)≤ε≤5.0×10^(10)s^(-1)).The results demonstrate that deformation mechanisms of isopachous Ti/Ni MNWs are determined by the layer thickness and strain rate.Four distinct strain rate regions in the tensile process can be discovered,which are small,intermediate,critical,and large strain rate regions.As the strain rate increases,the initial plastic behaviors transform from interface shear(the shortest sample)and grain reorientation(the longest sample)in small strain rate region to amorphization of crystalline structures(all samples)in large strain rate region.Microstructure evolutions reveal that the disparate tensile behaviors are ascribed to the atomic fractions of different structures in small strain rate region,and only related to collapse of crystalline atoms in high strain rate region.A layer thickness-strain rate-dependent mechanism diagram is given to illustrate the couple effect on the plastic deformation mechanisms of the isopachous nanowires.The results also indicate that the modulation ratio significantly affects the tensile properties of unequal Ti/Ni MNWs,but barely affect the plastic deformation mechanisms of the materials.The observations from this work will promote theoretical researches and practical applications of Ti/Ni MNWs.
