Multi-edge extended X-ray absorption fine structure(EXAFS)spectroscopy combined with reverse Monte Carlo(RMC)simulations was used to probe the details of element-specific local coordinations and component-dependent st...Multi-edge extended X-ray absorption fine structure(EXAFS)spectroscopy combined with reverse Monte Carlo(RMC)simulations was used to probe the details of element-specific local coordinations and component-dependent structure relaxations in single crystalline equiatomic CrMnFeCoNi high-entropy alloy as a function of the annealing temperature.Two representative states,namely a high-temperature state,created by annealing at 1373 K,and a low-temperature state,produced by long-term annealing at 993 K,were compared in detail.Specific features identified in atomic configurations of particular principal components indicate variations in the local environment distortions connected to different degrees of compositional disorder at the chosen representative temperatures.The detected changes provide new atomistic insights and correlate with the existence of kinks previously observed in the Arrhenius dependencies of component diffusion rates in the CrMnFeCoNi high-entropy alloy.展开更多
In-situ tensile experiments on pure Ti were performed in a transmission electron microscope at room temperature.The dynamic process of stress-induced hexagonal closed-packed(hcp)to face-centered cu-bic(fcc)structural ...In-situ tensile experiments on pure Ti were performed in a transmission electron microscope at room temperature.The dynamic process of stress-induced hexagonal closed-packed(hcp)to face-centered cu-bic(fcc)structural transformation ahead of a crack tip was captured at the atomic level.Intriguingly,a sliding behavior of the ensuing(0001)hcp/(1¯11)_(fcc) phase boundary was observed to further accommodate the plastic deformation until crack initiation.The sliding was accomplished via the successive conserva-tive glide of extended dislocations along the(0001)hcp/(1¯11)_(fcc) phase boundary.A molecular dynamics simulation was carried out to corroborate the experiments and the results confirm the new dislocation-mediated sliding mechanism.展开更多
Pd_(40)Ni_(40)P_(20)(at.%)samples with different enthalpy states were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast material.Subsequently,the underlying structural relaxation was studied ...Pd_(40)Ni_(40)P_(20)(at.%)samples with different enthalpy states were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast material.Subsequently,the underlying structural relaxation was studied by in-situ shear modulus measurements and modulated differential scanning calorimetry.The results show that high-pressure torsion leads to shear modulus softening and an increase of the nonreversible exothermic enthalpy,indicating a significant structural rejuvenation,while sub-Tg annealing causes shear modulus hardening and a decrease of the nonreversible exothermic enthalpy.The reversible endothermic effect which can reflect the fractional change of supercooled liquid with temperature was found to be almost identical for all samples,and independent of deformation or thermal history.The total heat flow can be well correlated with the shear modulus within the framework of interstitialcy theory.Furthermore,we demonstrate that the structural relaxation below Tg decouples into internal stress relaxation andβ-relaxation.In addition,this work indicates that the processes ofα-relaxation andβ-relaxation in the metallic glass are of similar structural origin but occur on different spatial scales.展开更多
基金the Helmholtz-Zentrum Berlin for the provision of access to synchrotron radiation facility and allocation of synchrotron radiation at the BAMline and KMC-3(CryoEXAFS end-station)beamlines of BESSY II at HZB.Yu.Chumlyakov(Tomsk State University,Russia)is acknowledged for the growth of single crystals.A.S.also acknowledges personal funding from CALIPSOplus project(Grant Agreement No.730872 from the EU Framework Programme for Research and Innovation HORIZON 2020)+1 种基金A.K.is thankful for the financial support from the Latvian Council of Science project No.lzp-2023/1-0476.S.D.acknowledges financial support by the German Research Foundation(DFG),project DI 1419/24-1.G.W.acknowledges financial support by DFG via SPP2006,project WI 1899/32-2.Institute of Solid State Physics,University of Latvia as the Center of Excellence has received funding from the EU Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No.739508,project CAMART2.
文摘Multi-edge extended X-ray absorption fine structure(EXAFS)spectroscopy combined with reverse Monte Carlo(RMC)simulations was used to probe the details of element-specific local coordinations and component-dependent structure relaxations in single crystalline equiatomic CrMnFeCoNi high-entropy alloy as a function of the annealing temperature.Two representative states,namely a high-temperature state,created by annealing at 1373 K,and a low-temperature state,produced by long-term annealing at 993 K,were compared in detail.Specific features identified in atomic configurations of particular principal components indicate variations in the local environment distortions connected to different degrees of compositional disorder at the chosen representative temperatures.The detected changes provide new atomistic insights and correlate with the existence of kinks previously observed in the Arrhenius dependencies of component diffusion rates in the CrMnFeCoNi high-entropy alloy.
基金The authors would like to acknowledge the financial sup-port of the National Key R&D Program of China(Grant No.2021YFA1200203)the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20210352,BK20200503,and BK20200019)+1 种基金the National Natural Science Foundation of China(Grant Nos.51905268,52101142,52001116,and 51871120)China Postdoc-toral Science Foundation(Grant No.2021M691581).
文摘In-situ tensile experiments on pure Ti were performed in a transmission electron microscope at room temperature.The dynamic process of stress-induced hexagonal closed-packed(hcp)to face-centered cu-bic(fcc)structural transformation ahead of a crack tip was captured at the atomic level.Intriguingly,a sliding behavior of the ensuing(0001)hcp/(1¯11)_(fcc) phase boundary was observed to further accommodate the plastic deformation until crack initiation.The sliding was accomplished via the successive conserva-tive glide of extended dislocations along the(0001)hcp/(1¯11)_(fcc) phase boundary.A molecular dynamics simulation was carried out to corroborate the experiments and the results confirm the new dislocation-mediated sliding mechanism.
基金financial support by German Research Foundation under the grant No.W11899/29-1the China Scholarship Council for its financial supportthe financial support from Russian Science Foundation under the grant No.20-62-46003(measurements of the shear modulus and discussion on the results)。
文摘Pd_(40)Ni_(40)P_(20)(at.%)samples with different enthalpy states were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast material.Subsequently,the underlying structural relaxation was studied by in-situ shear modulus measurements and modulated differential scanning calorimetry.The results show that high-pressure torsion leads to shear modulus softening and an increase of the nonreversible exothermic enthalpy,indicating a significant structural rejuvenation,while sub-Tg annealing causes shear modulus hardening and a decrease of the nonreversible exothermic enthalpy.The reversible endothermic effect which can reflect the fractional change of supercooled liquid with temperature was found to be almost identical for all samples,and independent of deformation or thermal history.The total heat flow can be well correlated with the shear modulus within the framework of interstitialcy theory.Furthermore,we demonstrate that the structural relaxation below Tg decouples into internal stress relaxation andβ-relaxation.In addition,this work indicates that the processes ofα-relaxation andβ-relaxation in the metallic glass are of similar structural origin but occur on different spatial scales.
