Using a special constant deflection device, the changes in dislocation configuration ahead of a loaded crack tip for 60Fe40Ni alloy. before and after magnetization in a magnetic field, have been studied in TEM. The re...Using a special constant deflection device, the changes in dislocation configuration ahead of a loaded crack tip for 60Fe40Ni alloy. before and after magnetization in a magnetic field, have been studied in TEM. The results showed that the magnetization for 60Fe40Ni alloy could enhance dislocation emission, multiplication and motion. Also, the mechanical properties of 60Fe40Ni alloy, in air and in the magnetic field respectively have been investigated using the slow strain rate tension. And the results indicated that magnetization could make the yield strength corresponding to decrease by 26 percent, but did not influence the ultimate tensile strength and the fracture strain, which showed that magnetization could enhance plastic deformation.展开更多
The plastic deformation of semiconductors,a process critical to their mechanical and electronic properties,involves various mechanisms such as dislocation motion and phase transition.Here,we systematically examined th...The plastic deformation of semiconductors,a process critical to their mechanical and electronic properties,involves various mechanisms such as dislocation motion and phase transition.Here,we systematically examined the temperature-dependent Peierls stress for 30°and 90°partial dislocations in cadmium telluride(CdTe),using a combination of molecular statics and molecular dynamics simulations with a machine-learning force field,as well as density functional theory simulations.Our findings reveal that the 0 K Peierls stresses for these partial dislocations in CdTe are relatively low,ranging from 0.52 GPa to 1.46 GPa,due to its significant ionic bonding characteristics.Notably,in the CdTe system containing either a 30°Cd-core or 90°Te-core partial dislocation,a phase transition from the zinc-blende phase to theβ-Sn-like phase is favored over dislocation motion.This suggests a competitive relationship between these two mechanisms,driven by the bonding characteristics within the dislocation core and the relatively low phase transition stress of∼1.00 GPa.Furthermore,we observed a general trend wherein the Peierls stress for partial dislocations in CdTe exhibits a temperature dependence,which decreases with increasing temperature,becoming lower than the phase transition stress at elevated temperatures.Consequently,the dominant deformation mechanism in CdTe shifts from solid-state phase transition at low temperatures to dislocation motion at high temperatures.This investigation uncovers a compelling interplay between dislocation motion and phase transition in the plastic deformation of CdTe,offering profound insights into the mechanical behavior and electronic performance of CdTe and other II-VI semiconductors.展开更多
A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,...A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.展开更多
The effects of minor Sc and Zr additions on the mechanical properties and microstructure evolution of Al Zn Mg Cu alloys were studied using tensile tests, scanning electron microscopy (SEM) and transmission electron m...The effects of minor Sc and Zr additions on the mechanical properties and microstructure evolution of Al Zn Mg Cu alloys were studied using tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ultimate tensile strength of the peak-aged Al Zn Mg Cu alloy is improved by about 105 MPa with the addition of 0.10% Zr. An increase of about 133 MPa is observed with the joint addition of 0.07% Sc and 0.07% Zr. For the alloys modified with the minor addition of Sc and Zr (0.14%), the main strengthening mechanisms of minor addition of Sc and Zr are fine-grain strengthening, sub-structure strengthening and the Orowan strengthening mechanism produced by the Al3(Sc,Zr) and Al3Zr dispersoids. The volume of Al3Zr particles is less than that of Al3(Sc,Zr) particles, but the distribution of Al3(Sc,Zr) particles is more dispersed throughout the matrix leading to pinning the dislocations motion and restraining the recrystallization more effectively.展开更多
Ultra-coarse grained cemented carbides are often used under conditions of concurrently applied stress and high temperature.Improvement of high-temperature mechanical performance of ultra-coarse grained cemented carbid...Ultra-coarse grained cemented carbides are often used under conditions of concurrently applied stress and high temperature.Improvement of high-temperature mechanical performance of ultra-coarse grained cemented carbides is highly desirable but still a big challenge.In this study,it is proposed that the hightemperature compression strength of ultra-coarse cemented carbides can be enhanced by modulating hard matrix grains by activated Ta C nanoparticles,through solid solution strengthening of Ta atoms.Based on the designed experiments and microstructural characterizations combined with finite element simulations,the grain morphology,stress distribution and dislocation configuration were studied in detail for ultra-coarse grained cemented carbides.The mechanisms of Ta dissolving in WC crystal and strengthening ultra-coarse grains through interaction with dislocations were disclosed from the atomic scale.This study opens a new perspective to modulate hard phases of cemented carbides for improving their hightemperature performance,which will be applicable to a variety of cermet and ceramic-based composite materials.展开更多
TEM (Transmission Electron Microscope) observations show that corrosion process during stress corrosion cracking (SCC) enhances dislocation emission and motion; and microcrack of SCC initiates when the corrosion-enhan...TEM (Transmission Electron Microscope) observations show that corrosion process during stress corrosion cracking (SCC) enhances dislocation emission and motion; and microcrack of SCC initiates when the corrosion-enhanced dislocation emission and motion reaches a certain condition. The passive film or dealloyed layer formed during corrosion or SCC can induce a large tensile stress, which can assist the applied stress to enhance dislocation emission and motion, and then SCC occurs. Experiments show that the variation of SCC susceptibility of brass,α-Ti and stainless steel with the applied potential and pH value of the solution is consistent with that of the corrosion-induced additive stress. Molecular dynamics simulations show that a dealloyed layer can generate a tensile stress; and the corrosion (dealloyed layer)-induced tensile stress can assist the applied stress to enhance dislocation emission and crack propagation.展开更多
This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate o...This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate of 1–0.001 s^(−1).The microstructure evolution and deformation mechanisms were revealed through parent phase reconstruction.During the deformation,Dynamic Recrystallization(DRX)was preferentially developed in TiBw rich region due to the TiBw supplying dislocation pile-up and heterogeneous nucleation sites.The main DRX mechanisms included continuous and discontinuous DRX.The microstructure in TiBw lean region was closely related to strain rates,which was deformed microstructure at high strain rates but DRXed microstructure at low strain rates.The primary mechanisms of deformation were governed by dislocation motion.Besides,in TiBw rich region,Grain Boundary Sliding(GBS)coordinated the deformation due to DRX.However,GBS was hindered again at low strain rates due to the increase of DRXed grain size,contributing to a gradual rise in flow stress.展开更多
Tungsten has promising applications in high-radiation,high-erosion and high-impact environments.Laser peening is an effective method to enhance the surface mechanical properties of tungsten materials.However,the ultra...Tungsten has promising applications in high-radiation,high-erosion and high-impact environments.Laser peening is an effective method to enhance the surface mechanical properties of tungsten materials.However,the ultrafast dynamic mechanism of defect evolutions induced by laser shockwave in tungsten lattice is unclear.Here,we investigated the evolutions and interactions of various defects under ultrafast compressive process in tungsten lattice using molecular dynamic method.The results confirm the brittleness of tungsten and reveal that void can reduce the yield strain and strength of the tungsten lattice by accelerating defect mesh extension and promoting the dislocation nucleation around itself.Dislocation density is increased with compressive strain rate.Meanwhile,dislocation multiplication and motion reduce the elastic stage and play a dominant role during the plastic deformation of tungsten lattice.Additionally,void can disrupt the dislocation displacement and promote the pinning effect on dislocations by defect mesh extension.展开更多
基金supported by the National Natural Science Foundation of China(No.19891180)
文摘Using a special constant deflection device, the changes in dislocation configuration ahead of a loaded crack tip for 60Fe40Ni alloy. before and after magnetization in a magnetic field, have been studied in TEM. The results showed that the magnetization for 60Fe40Ni alloy could enhance dislocation emission, multiplication and motion. Also, the mechanical properties of 60Fe40Ni alloy, in air and in the magnetic field respectively have been investigated using the slow strain rate tension. And the results indicated that magnetization could make the yield strength corresponding to decrease by 26 percent, but did not influence the ultimate tensile strength and the fracture strain, which showed that magnetization could enhance plastic deformation.
基金supported by the National Science Foundation(No.CMMI-2019459).
文摘The plastic deformation of semiconductors,a process critical to their mechanical and electronic properties,involves various mechanisms such as dislocation motion and phase transition.Here,we systematically examined the temperature-dependent Peierls stress for 30°and 90°partial dislocations in cadmium telluride(CdTe),using a combination of molecular statics and molecular dynamics simulations with a machine-learning force field,as well as density functional theory simulations.Our findings reveal that the 0 K Peierls stresses for these partial dislocations in CdTe are relatively low,ranging from 0.52 GPa to 1.46 GPa,due to its significant ionic bonding characteristics.Notably,in the CdTe system containing either a 30°Cd-core or 90°Te-core partial dislocation,a phase transition from the zinc-blende phase to theβ-Sn-like phase is favored over dislocation motion.This suggests a competitive relationship between these two mechanisms,driven by the bonding characteristics within the dislocation core and the relatively low phase transition stress of∼1.00 GPa.Furthermore,we observed a general trend wherein the Peierls stress for partial dislocations in CdTe exhibits a temperature dependence,which decreases with increasing temperature,becoming lower than the phase transition stress at elevated temperatures.Consequently,the dominant deformation mechanism in CdTe shifts from solid-state phase transition at low temperatures to dislocation motion at high temperatures.This investigation uncovers a compelling interplay between dislocation motion and phase transition in the plastic deformation of CdTe,offering profound insights into the mechanical behavior and electronic performance of CdTe and other II-VI semiconductors.
基金financial support from the National Natural Science Foundation of China(Nos.52104306,52274301,52334009)the Aeronautical Science Foundation of China(No.2023Z0530S6005)+3 种基金the National Key Research and Development Program of China(No.2023YFB3712401)the Science and Technology Commission of Shanghai Municipality(No.21DZ1208900)the Academician Workstation of Kunming University of Science and Technology(2024),the Ningbo Yongjiang Talent-Introduction Programme(No.2022A-023-C)the Zhejiang Phenomenological Materials Technology Co.,Ltd.,China.
文摘A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.
基金Project (2016B090931004) supported by the Scientific and Research Plan of Guangdong Province, ChinaProject (51601229) supported by the National Natural Science Foundation of China。
文摘The effects of minor Sc and Zr additions on the mechanical properties and microstructure evolution of Al Zn Mg Cu alloys were studied using tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ultimate tensile strength of the peak-aged Al Zn Mg Cu alloy is improved by about 105 MPa with the addition of 0.10% Zr. An increase of about 133 MPa is observed with the joint addition of 0.07% Sc and 0.07% Zr. For the alloys modified with the minor addition of Sc and Zr (0.14%), the main strengthening mechanisms of minor addition of Sc and Zr are fine-grain strengthening, sub-structure strengthening and the Orowan strengthening mechanism produced by the Al3(Sc,Zr) and Al3Zr dispersoids. The volume of Al3Zr particles is less than that of Al3(Sc,Zr) particles, but the distribution of Al3(Sc,Zr) particles is more dispersed throughout the matrix leading to pinning the dislocations motion and restraining the recrystallization more effectively.
基金supported by the National Key Program of Research and Development(No.2018YFB0703902)the National Natural Science Foundation of China(Nos.51631002,51621003,52101003,52171061,U20A20236)。
文摘Ultra-coarse grained cemented carbides are often used under conditions of concurrently applied stress and high temperature.Improvement of high-temperature mechanical performance of ultra-coarse grained cemented carbides is highly desirable but still a big challenge.In this study,it is proposed that the hightemperature compression strength of ultra-coarse cemented carbides can be enhanced by modulating hard matrix grains by activated Ta C nanoparticles,through solid solution strengthening of Ta atoms.Based on the designed experiments and microstructural characterizations combined with finite element simulations,the grain morphology,stress distribution and dislocation configuration were studied in detail for ultra-coarse grained cemented carbides.The mechanisms of Ta dissolving in WC crystal and strengthening ultra-coarse grains through interaction with dislocations were disclosed from the atomic scale.This study opens a new perspective to modulate hard phases of cemented carbides for improving their hightemperature performance,which will be applicable to a variety of cermet and ceramic-based composite materials.
基金The work was financially supported by the special Funds for the Major state Basic Research Projects(No.G19990650)the National Natural Science of China No.50231020).
文摘TEM (Transmission Electron Microscope) observations show that corrosion process during stress corrosion cracking (SCC) enhances dislocation emission and motion; and microcrack of SCC initiates when the corrosion-enhanced dislocation emission and motion reaches a certain condition. The passive film or dealloyed layer formed during corrosion or SCC can induce a large tensile stress, which can assist the applied stress to enhance dislocation emission and motion, and then SCC occurs. Experiments show that the variation of SCC susceptibility of brass,α-Ti and stainless steel with the applied potential and pH value of the solution is consistent with that of the corrosion-induced additive stress. Molecular dynamics simulations show that a dealloyed layer can generate a tensile stress; and the corrosion (dealloyed layer)-induced tensile stress can assist the applied stress to enhance dislocation emission and crack propagation.
基金financially supported by the National Natural Science Foundation of China(No.52375324).
文摘This research explored the hot deformation behavior of TiBw/(TA15-Si)composite with a network structure fabricated by hot pressing sintering.Hot compression test was conducted at 1000–1020°C under strain rate of 1–0.001 s^(−1).The microstructure evolution and deformation mechanisms were revealed through parent phase reconstruction.During the deformation,Dynamic Recrystallization(DRX)was preferentially developed in TiBw rich region due to the TiBw supplying dislocation pile-up and heterogeneous nucleation sites.The main DRX mechanisms included continuous and discontinuous DRX.The microstructure in TiBw lean region was closely related to strain rates,which was deformed microstructure at high strain rates but DRXed microstructure at low strain rates.The primary mechanisms of deformation were governed by dislocation motion.Besides,in TiBw rich region,Grain Boundary Sliding(GBS)coordinated the deformation due to DRX.However,GBS was hindered again at low strain rates due to the increase of DRXed grain size,contributing to a gradual rise in flow stress.
基金financially support from the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA25040201)the National Natural Science Foundation of China(Grant No.51727901)support provided by the Deanship of Scientific Research(DSR)at King Fahd University of Petroleum&Minerals(KFUPM)(Grant No.DF201020)
文摘Tungsten has promising applications in high-radiation,high-erosion and high-impact environments.Laser peening is an effective method to enhance the surface mechanical properties of tungsten materials.However,the ultrafast dynamic mechanism of defect evolutions induced by laser shockwave in tungsten lattice is unclear.Here,we investigated the evolutions and interactions of various defects under ultrafast compressive process in tungsten lattice using molecular dynamic method.The results confirm the brittleness of tungsten and reveal that void can reduce the yield strain and strength of the tungsten lattice by accelerating defect mesh extension and promoting the dislocation nucleation around itself.Dislocation density is increased with compressive strain rate.Meanwhile,dislocation multiplication and motion reduce the elastic stage and play a dominant role during the plastic deformation of tungsten lattice.Additionally,void can disrupt the dislocation displacement and promote the pinning effect on dislocations by defect mesh extension.
