We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidificat...We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys.Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed.They include introduction,high-gradient magnetic field effects,migration behavior of solute and particles in high-gradient magnetic fields,microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles,and properties of materials modified by high-gradient magnetic field-tailored microstructure.Selected examples of binary and multiphase alloy systems are presented and examined,with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution.Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.展开更多
This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase fa...This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase face-centered cubic structure while lowering the stacking fault energy to encourage the formation of deformation twins and stacking faults by altering the equiatomic composition of the alloy.The processing strategy applied helped create a hierarchical grain size gradient microstructure with a high nanotwins population.This was achieved by means of rotationally accelerated shot peening(RASP).The non-equiatomic Co Cr Fe Mn Ni high-entropy alloy achieved a yield strength of 750 MPa,a tensile strength of 1050 MPa,and tensile uniform elongation of 27.5%.The toughness of the alloy was 2.53×10^(10)k J/m^(3),which is about 2 times that of the same alloy without the RASP treatment.The strength increase is attributed to the effects of grain boundary strengthening,dislocation strengthening,twin strengthening,and hetero-deformation strengthening associated with the heterogeneous microstructure of the alloy.The concurrent occurrence of the multiple deformation mechanisms,i.e.,dislocation deformation,twining deformation and microband deformation,contributes to achieving a suitable strain hardening of the alloy that helps to prevent early necking and to assure steady plastic deformation for high toughness.展开更多
Research and design of a C-band (5712 MHz) high-gradient traveling-wave accelerating structure is being carried out at Shanghai Institute of Applied Physics,Chinese Academy of Sciences.The structure consists of 53 reg...Research and design of a C-band (5712 MHz) high-gradient traveling-wave accelerating structure is being carried out at Shanghai Institute of Applied Physics,Chinese Academy of Sciences.The structure consists of 53 regular disk-loaded cells and two waveguide couplers,and its length is about 1 m.This paper presents a design method for the accelerating structure,an experimental model and the preliminary results of an RF cold test of the model structure.展开更多
Due to the fact that ballastless tracks in highspeed railways are not only subjected to repeated train–track dynamic interaction loads,but also suffer from complex environmental loads,the fundamental understanding of...Due to the fact that ballastless tracks in highspeed railways are not only subjected to repeated train–track dynamic interaction loads,but also suffer from complex environmental loads,the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks.This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways,particularly focusing on the typical interface damage evolution between track layers.To this end,a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load(TGL)followed by the same cycle of the positive TGL.Subsequently,the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model.Finally,the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method.Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage;the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities;the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface,which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehic展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51425401,51690161,51574073,and 51774086)Fundamental Research Funds for the Central Universities,China(Grant Nos.N170902002 and N170908001)Liaoning Innovative Research Team in University,China(Grant No.LT2017011)
文摘We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys.Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed.They include introduction,high-gradient magnetic field effects,migration behavior of solute and particles in high-gradient magnetic fields,microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles,and properties of materials modified by high-gradient magnetic field-tailored microstructure.Selected examples of binary and multiphase alloy systems are presented and examined,with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution.Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.
基金the support of Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(51988101)NSFC programs(52071003,91860202,11604006)+4 种基金Beijing Municipal Education Commission Project(PXM2020014204000021 and PXM2019014204500032)Beijing Outstanding Young Scientists Projects(BJJWZYJH01201910005018)Beijing Natural Science Foundation(Z180014)“111”project(DB18015)the support by the Australian Research Council(DP190102990)to his work in this study。
文摘This study explored a multi-mechanism approach to improving the mechanical properties of a Co CrFe Mn Ni high-entropy alloy through non-equiatomic alloy design and processing.The alloy design ensures a single-phase face-centered cubic structure while lowering the stacking fault energy to encourage the formation of deformation twins and stacking faults by altering the equiatomic composition of the alloy.The processing strategy applied helped create a hierarchical grain size gradient microstructure with a high nanotwins population.This was achieved by means of rotationally accelerated shot peening(RASP).The non-equiatomic Co Cr Fe Mn Ni high-entropy alloy achieved a yield strength of 750 MPa,a tensile strength of 1050 MPa,and tensile uniform elongation of 27.5%.The toughness of the alloy was 2.53×10^(10)k J/m^(3),which is about 2 times that of the same alloy without the RASP treatment.The strength increase is attributed to the effects of grain boundary strengthening,dislocation strengthening,twin strengthening,and hetero-deformation strengthening associated with the heterogeneous microstructure of the alloy.The concurrent occurrence of the multiple deformation mechanisms,i.e.,dislocation deformation,twining deformation and microband deformation,contributes to achieving a suitable strain hardening of the alloy that helps to prevent early necking and to assure steady plastic deformation for high toughness.
基金supported by the Program of Shanghai Subject Chief Scientist-Natural Science Foundation (Key Program)(08XD14054)
文摘Research and design of a C-band (5712 MHz) high-gradient traveling-wave accelerating structure is being carried out at Shanghai Institute of Applied Physics,Chinese Academy of Sciences.The structure consists of 53 regular disk-loaded cells and two waveguide couplers,and its length is about 1 m.This paper presents a design method for the accelerating structure,an experimental model and the preliminary results of an RF cold test of the model structure.
基金the National Natural Science Foundation of China(Nos.51708457,11790283,and 51978587)the Fund from State Key Laboratory of Traction Power(2019TPL-T16)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)the 111 Project(Grant No.B16041)。
文摘Due to the fact that ballastless tracks in highspeed railways are not only subjected to repeated train–track dynamic interaction loads,but also suffer from complex environmental loads,the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks.This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways,particularly focusing on the typical interface damage evolution between track layers.To this end,a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load(TGL)followed by the same cycle of the positive TGL.Subsequently,the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model.Finally,the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method.Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage;the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities;the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface,which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehic
