Impact of texture type on the magnetic properties of ultrahigh density perpendicular magnetic recording media L1_(0)-FePt thin film was investigated,so were the texture formation and evolution mechanism.Reuss,Voigt,an...Impact of texture type on the magnetic properties of ultrahigh density perpendicular magnetic recording media L1_(0)-FePt thin film was investigated,so were the texture formation and evolution mechanism.Reuss,Voigt,and Hill models were used to determine the anisotropic elastic modulus of L1_(0)-FePt thin film with fiber texture.Then,the elastic strain energies of thin films under various stress conditions were calculated.Results reveal that the stress condition has a significant influence on the fiber texture evolution.When the L1_(0)-FePt thin film is subjected to compressive in-plane strain prior to ordering phase transformation,the formation of{100}fiber texture is promoted.On the contrary,the ordering phase transformation under tensile in-plane strain promotes the{001}fiber texture formation.展开更多
L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by ...L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by recent studies on the effect of vacancy defects on structural ordering,we proposed an intentional vacancy defect design strategy for directly synthesizing highly ordered FePt NPs.In the present work,we used the first-principle calculations to investigate the influence of doping typical elements(Cu,Ag,and Pb)on the vacancy formation energy(E_(vac))of FePt NPs.The vacancy defects were effectively formed by introducing elements of larger atomic radii and higher propensity for segregation into the FePt lattice,facilitating the diffusion of Fe and Pt atoms.The Pb doping showed remarkable efficacy in promoting the ordering transition.Experimentally,wet-chemical synthesis confirmed the success of the proposed strategy in achieving highly ordered L1_(0)-FePt NPs with exceptional magnetic properties and super-fine size(ordering degree of 0.896,impressive coercivity of 21.74 kOe,and small particle size of 9.02 nm).Additionally,we have deduced a diffusion model elucidating the formation process of the ordered FePt NPs,focusing on the migration of Pb atoms from the center to the surface of the particles.This migration is demonstrated to generate more vacancies and promote the transition to the ordered L1_(0)-FePt phase.The findings of this research offer valuable insights into synthesizing highly ordered and ultrafine L1_(0)-type nanomaterials.展开更多
Eutectic high-entropy alloys(EHEAs)that combine the advantages of HEAs and eutectic alloys are promising materials for high-temperature environments.However,the mechanical properties of currently developed EHEAs still...Eutectic high-entropy alloys(EHEAs)that combine the advantages of HEAs and eutectic alloys are promising materials for high-temperature environments.However,the mechanical properties of currently developed EHEAs still cannot meet the servicing requirements.Here,we propose a strategy to optimize the tensile properties in a Al_(21)Co_(19.5)Fe_(9.5)Ni_(50)EHEA by regulating the phase transformation and precipitation features.The results showed that the as-cast Al_(21)Co_(19.5)Fe_(9.5)Ni_(50)EHEA mainly consists of face-centered cubic(FCC)and B2 phases showing a lamellar morphology,and the FCC and B2 phases keep a stable K-S orientation relationship.Solution treatment at 900 and 1100°C followed by furnace cooling to room temperature leads to a significant precipitation of L1_(2)phases within the FCC phases.In the subsequent tensile deformation process,dispersed L1_(2)phases and the transformation from B2 to L1_(0)phases can significantly enhance the yield strength of the designed EHEA.Furthermore,solution treatment at the same temperature,followed by rapid water quenching,results in the appearance of numerous L1_(0)phases within the B2 phases.The transformation from L1_(0)to B2 phases during subsequent tensile deformation can make the B2 and FCC phases return to a K-S orientation relationship.This,in turn,reduces the tendency for dislocation pile-ups at the phase interfaces and improves the ductility.We believe that this work will provide some new references for designing EHEAs with excellent mechanical properties.展开更多
基金Inner Mongolia Natural Science Foundation Project(2020LH05028)。
文摘Impact of texture type on the magnetic properties of ultrahigh density perpendicular magnetic recording media L1_(0)-FePt thin film was investigated,so were the texture formation and evolution mechanism.Reuss,Voigt,and Hill models were used to determine the anisotropic elastic modulus of L1_(0)-FePt thin film with fiber texture.Then,the elastic strain energies of thin films under various stress conditions were calculated.Results reveal that the stress condition has a significant influence on the fiber texture evolution.When the L1_(0)-FePt thin film is subjected to compressive in-plane strain prior to ordering phase transformation,the formation of{100}fiber texture is promoted.On the contrary,the ordering phase transformation under tensile in-plane strain promotes the{001}fiber texture formation.
基金supported by the National Key Research and Development Program of China(Nos.2020YFA0907300 and 2021YFB3501404)the National Natural Science Foundation of China(Nos.52301234,52371179,and 52071070)+1 种基金the Doctoral Start-up Foundation of Liaoning Province(No.2023-BS-059)the Fundamental Research Funds for the Central Universities(No.N2309002).
文摘L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by recent studies on the effect of vacancy defects on structural ordering,we proposed an intentional vacancy defect design strategy for directly synthesizing highly ordered FePt NPs.In the present work,we used the first-principle calculations to investigate the influence of doping typical elements(Cu,Ag,and Pb)on the vacancy formation energy(E_(vac))of FePt NPs.The vacancy defects were effectively formed by introducing elements of larger atomic radii and higher propensity for segregation into the FePt lattice,facilitating the diffusion of Fe and Pt atoms.The Pb doping showed remarkable efficacy in promoting the ordering transition.Experimentally,wet-chemical synthesis confirmed the success of the proposed strategy in achieving highly ordered L1_(0)-FePt NPs with exceptional magnetic properties and super-fine size(ordering degree of 0.896,impressive coercivity of 21.74 kOe,and small particle size of 9.02 nm).Additionally,we have deduced a diffusion model elucidating the formation process of the ordered FePt NPs,focusing on the migration of Pb atoms from the center to the surface of the particles.This migration is demonstrated to generate more vacancies and promote the transition to the ordered L1_(0)-FePt phase.The findings of this research offer valuable insights into synthesizing highly ordered and ultrafine L1_(0)-type nanomaterials.
基金supported by the funds of the Shanghai Sailing Program,the National Natural Science Foundation of China(No.52104386)the Xi’an Association for Science and Technology Young Talents Lifting Program,and the State Key Laboratory of Solidification Processing(NPU),China(No.2022-TS-08).
文摘Eutectic high-entropy alloys(EHEAs)that combine the advantages of HEAs and eutectic alloys are promising materials for high-temperature environments.However,the mechanical properties of currently developed EHEAs still cannot meet the servicing requirements.Here,we propose a strategy to optimize the tensile properties in a Al_(21)Co_(19.5)Fe_(9.5)Ni_(50)EHEA by regulating the phase transformation and precipitation features.The results showed that the as-cast Al_(21)Co_(19.5)Fe_(9.5)Ni_(50)EHEA mainly consists of face-centered cubic(FCC)and B2 phases showing a lamellar morphology,and the FCC and B2 phases keep a stable K-S orientation relationship.Solution treatment at 900 and 1100°C followed by furnace cooling to room temperature leads to a significant precipitation of L1_(2)phases within the FCC phases.In the subsequent tensile deformation process,dispersed L1_(2)phases and the transformation from B2 to L1_(0)phases can significantly enhance the yield strength of the designed EHEA.Furthermore,solution treatment at the same temperature,followed by rapid water quenching,results in the appearance of numerous L1_(0)phases within the B2 phases.The transformation from L1_(0)to B2 phases during subsequent tensile deformation can make the B2 and FCC phases return to a K-S orientation relationship.This,in turn,reduces the tendency for dislocation pile-ups at the phase interfaces and improves the ductility.We believe that this work will provide some new references for designing EHEAs with excellent mechanical properties.
