Pre-stretching and annealing treatments were conducted on twin roll cast Mg-2Al-1Zn-1Ca(AZX211,in wt.%)plates with a rare earth-like texture.Varying amounts of deformation were applied along the rolling direction(RD)a...Pre-stretching and annealing treatments were conducted on twin roll cast Mg-2Al-1Zn-1Ca(AZX211,in wt.%)plates with a rare earth-like texture.Varying amounts of deformation were applied along the rolling direction(RD)and transverse direction(TD)of AZX211 alloy in order to modify its mechanical proper-ties at room temperature.The results demonstrate that pre-stretching treatment effectively enhances the yield strength(YS),especially along the RD.The strengthening mechanism is attributed to the production of a large number of dislocations and sub-grain boundaries,but the work-hardening ability of the plate will be greatly weakened.Additionally,annealing treatment substantially improves the plasticity and in-plane anisotropy and restores the work-hardening ability.The notable distinction in the pre-stretching process between different directions lies in the underlying deformation mechanism.In case of RD,de-formation is predominantly governed by the slip mechanism of{0002}{11−20}basal slip and{10−10}{11−20}prismatic slip,while along the TD,deformation is primarily controlled by{0002}{11−20}basal slip without significant twinning deformation.When a 6%pre-stretching is conducted,the initial rare earth-like texture of the sample transforms into a symmetrically distributed double-peak basal texture,accompanied by grain refinement.This texture transformation is chiefly due to the dominance of{0002}{11−20}basal slip-driven deformation.Moreover,the annealed sample maintains a strong basal texture,owing to strain-induced recrystallization.展开更多
Fe-based superconductors represent a fascinating class of materials,extensively studied for their complex interplay of superconductivity,magnetism,spin density waves,and nematicity,along with the interactions among th...Fe-based superconductors represent a fascinating class of materials,extensively studied for their complex interplay of superconductivity,magnetism,spin density waves,and nematicity,along with the interactions among these orders.An intriguing yet unexplained phenomenon observed in Fe-based superconductors is the emergence of superconductivity below 25K in the non-superconducting parent compound SrFe_(2)As_(2)following exposure to water at its surface.In this study,we employed in situ angle-resolved photoemission spectroscopy and low-energy electron diffraction to meticulously examine the electronic structure evolution of SrFe_(2)As_(2)upon in situ water dosing.Our findings indicate that water dosing markedly attenuates the spin density wave phase and surface Sr reconstruction while preserving the nematic order in SrFe_(2)As_(2).Furthermore,we detected an enhancement in the spectral weight of bands near the Fermi level.Our observations highlight the critical role of the intricate interplay among various orders induced by water dosing,which effectively modifies the band structure and favors the emergence of superconductivity in SrFe_(2)As_(2).展开更多
This study investigates the influence of varying rolling reduction on the evolution of microstructure and mechanical properties of Mg–10Gd(in wt%)alloys by caliber rolling(CR).By increasing the rolling reduction from...This study investigates the influence of varying rolling reduction on the evolution of microstructure and mechanical properties of Mg–10Gd(in wt%)alloys by caliber rolling(CR).By increasing the rolling reduction from 45%to 65%,a uniform bimodal structure is obtained in which coarse grains(CGs)larger than 10μm are surrounded by fine grains(FGs).The Mg–Gd alloy subjected to 65%reduction exhibits superior mechanical properties,i.e.yield strength(YS)of~424 MPa,ultimate tensile strength(UTS)of~500 MPa and elongation(El.)of~3.3%.The synergistic improvement in strength and ductility is primarily attributed to the combined effects of low-angle grain boundary(LAGB)strengthening,precipitation strengthening,and the coordinated deformation exhibited by the bimodal structure.In addition,caliber rolling also provides a novel approach for the design of Mg alloys with uniform bimodal structures that exhibit both high strength and ductility.展开更多
The coarsening kinetics of a two-phase mixture with a large diffusional mobility disparity between the two phases is studied using a variable-mobility Cahn Hilliard equation.The semi-implicit spectral numerical techni...The coarsening kinetics of a two-phase mixture with a large diffusional mobility disparity between the two phases is studied using a variable-mobility Cahn Hilliard equation.The semi-implicit spectral numerical technique was employed,and a number of interpolation functions are considered for describing the change in diffusion mobility across the interface boundary from one phase to another.The coarsening rate of domain size was measured using both structure and pair correlation functions as well as the direct computation of particle sizes in real space for the case that the coarsening phase consists of dispersed particles.We discovered that the average size(R)versus time(t)follows the R^(10/3)∝t law,in contrast to the conventional LSW theory,R^(3)∝t,and the interface-diffusion dominated two-phase coarsening,R^(4)∝t.展开更多
In recent years,Fourier spectral methods have emerged as competitive numerical methods for large-scale phase field simulations of microstructures in computational materials sciences.To further improve their effectiven...In recent years,Fourier spectral methods have emerged as competitive numerical methods for large-scale phase field simulations of microstructures in computational materials sciences.To further improve their effectiveness,we recently developed a new adaptive Fourier-spectral semi-implicit method(AFSIM)for solving the phase field equation by combining an adaptive moving mesh method and the semi-implicit Fourier spectral algorithm.In this paper,we present the application of AFSIM to the Cahn-Hilliard equation with inhomogeneous,anisotropic elasticity.Numerical implementations and test examples in both two and three dimensions are considered with a particular illustration using the well-studied example of mis-fitting particles in a solid as they approach to their equilibrium shapes.It is shown that significant savings in memory and computational time is achieved while accurate solutions are preserved.展开更多
基金supported by the National Natural Science Foundation of China(No.52001106)Hebei province(No.E2022202158).
文摘Pre-stretching and annealing treatments were conducted on twin roll cast Mg-2Al-1Zn-1Ca(AZX211,in wt.%)plates with a rare earth-like texture.Varying amounts of deformation were applied along the rolling direction(RD)and transverse direction(TD)of AZX211 alloy in order to modify its mechanical proper-ties at room temperature.The results demonstrate that pre-stretching treatment effectively enhances the yield strength(YS),especially along the RD.The strengthening mechanism is attributed to the production of a large number of dislocations and sub-grain boundaries,but the work-hardening ability of the plate will be greatly weakened.Additionally,annealing treatment substantially improves the plasticity and in-plane anisotropy and restores the work-hardening ability.The notable distinction in the pre-stretching process between different directions lies in the underlying deformation mechanism.In case of RD,de-formation is predominantly governed by the slip mechanism of{0002}{11−20}basal slip and{10−10}{11−20}prismatic slip,while along the TD,deformation is primarily controlled by{0002}{11−20}basal slip without significant twinning deformation.When a 6%pre-stretching is conducted,the initial rare earth-like texture of the sample transforms into a symmetrically distributed double-peak basal texture,accompanied by grain refinement.This texture transformation is chiefly due to the dominance of{0002}{11−20}basal slip-driven deformation.Moreover,the annealed sample maintains a strong basal texture,owing to strain-induced recrystallization.
基金supported by the National Nature Science Foundation of China[Grant Nos.92365204 and 12274298(Z.K.Liu)]the National Key R&D program of China[Grant No.2022YFA1604400/03(Z.K.Liu)]Zhangjiang Laboratory(Y.M.Zhang).The authors thank BL02B at the Shanghai Synchrotron Radiation Facility supported by the National Natural Science Foundation of China(Contract No.11227902).
文摘Fe-based superconductors represent a fascinating class of materials,extensively studied for their complex interplay of superconductivity,magnetism,spin density waves,and nematicity,along with the interactions among these orders.An intriguing yet unexplained phenomenon observed in Fe-based superconductors is the emergence of superconductivity below 25K in the non-superconducting parent compound SrFe_(2)As_(2)following exposure to water at its surface.In this study,we employed in situ angle-resolved photoemission spectroscopy and low-energy electron diffraction to meticulously examine the electronic structure evolution of SrFe_(2)As_(2)upon in situ water dosing.Our findings indicate that water dosing markedly attenuates the spin density wave phase and surface Sr reconstruction while preserving the nematic order in SrFe_(2)As_(2).Furthermore,we detected an enhancement in the spectral weight of bands near the Fermi level.Our observations highlight the critical role of the intricate interplay among various orders induced by water dosing,which effectively modifies the band structure and favors the emergence of superconductivity in SrFe_(2)As_(2).
基金financial support from the National Natural Science Foundation of China(51701060,52001106)Hebei Province(E2022202158),the foundation of the Strengthening Program(2019-JCJQ-142-00)。
文摘This study investigates the influence of varying rolling reduction on the evolution of microstructure and mechanical properties of Mg–10Gd(in wt%)alloys by caliber rolling(CR).By increasing the rolling reduction from 45%to 65%,a uniform bimodal structure is obtained in which coarse grains(CGs)larger than 10μm are surrounded by fine grains(FGs).The Mg–Gd alloy subjected to 65%reduction exhibits superior mechanical properties,i.e.yield strength(YS)of~424 MPa,ultimate tensile strength(UTS)of~500 MPa and elongation(El.)of~3.3%.The synergistic improvement in strength and ductility is primarily attributed to the combined effects of low-angle grain boundary(LAGB)strengthening,precipitation strengthening,and the coordinated deformation exhibited by the bimodal structure.In addition,caliber rolling also provides a novel approach for the design of Mg alloys with uniform bimodal structures that exhibit both high strength and ductility.
基金the financial supports from the National Science Foundation under the grant number DMR-0710483(Chen)NSF-DMS 0712744(Du)+1 种基金DMR-0510180(Liu)DMR-0710484(K.G.Wang).
文摘The coarsening kinetics of a two-phase mixture with a large diffusional mobility disparity between the two phases is studied using a variable-mobility Cahn Hilliard equation.The semi-implicit spectral numerical technique was employed,and a number of interpolation functions are considered for describing the change in diffusion mobility across the interface boundary from one phase to another.The coarsening rate of domain size was measured using both structure and pair correlation functions as well as the direct computation of particle sizes in real space for the case that the coarsening phase consists of dispersed particles.We discovered that the average size(R)versus time(t)follows the R^(10/3)∝t law,in contrast to the conventional LSW theory,R^(3)∝t,and the interface-diffusion dominated two-phase coarsening,R^(4)∝t.
基金This work has been supported by the National Science Foundation Information Technol-ogy Research Project(NSF-ITR)through Grant DMR-0205232The work of Qiang Du is also supported by NSF-DMS 0712744.
文摘In recent years,Fourier spectral methods have emerged as competitive numerical methods for large-scale phase field simulations of microstructures in computational materials sciences.To further improve their effectiveness,we recently developed a new adaptive Fourier-spectral semi-implicit method(AFSIM)for solving the phase field equation by combining an adaptive moving mesh method and the semi-implicit Fourier spectral algorithm.In this paper,we present the application of AFSIM to the Cahn-Hilliard equation with inhomogeneous,anisotropic elasticity.Numerical implementations and test examples in both two and three dimensions are considered with a particular illustration using the well-studied example of mis-fitting particles in a solid as they approach to their equilibrium shapes.It is shown that significant savings in memory and computational time is achieved while accurate solutions are preserved.
