The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the funct...The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy . The binding energy of with respect to was calculated to be 0.8857 a.u. This means that the cluster ofmay be formed in the body-centered cubic structure of .展开更多
Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure t...Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.展开更多
The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cub...The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.展开更多
Submicron and nanostructured body-centered cubic(BCC) metals exhibit unusual mechanical performance compared to their bulk coarse-grained counterparts, including high yield strength and outstanding ductility. These pr...Submicron and nanostructured body-centered cubic(BCC) metals exhibit unusual mechanical performance compared to their bulk coarse-grained counterparts, including high yield strength and outstanding ductility. These properties are important for their applications in micro-, nano-and even atomic-scale devices as well as for their usages as components for enhancing the performances of structural materials. One aspect of the unusual mechanical properties of small-sized BCC metals is closely related to their dimensional confinement. Decreasing the dimensions of single crystalline metals or the grain sizes of polycrystalline metals contributes significantly to the strengthening of the small-sized BCC metals.In the last decade, significant progress has been achieved in understanding the plasticity and deformation behaviors of small-sized BCC metals. This paper aims to provide a comprehensive review on the current understanding of size effects on the plasticity and deformation mechanisms of small-sized BCC metals. The techniques used for in situ characterization of the deformation behavior and mechanical properties of small-sized samples are also presented.展开更多
High-entropy alloys greatly expand the alloy design range and offer new possibilities for improving material performance.Based on the worldwide research efforts in the last decade,the excellent mechanical properties a...High-entropy alloys greatly expand the alloy design range and offer new possibilities for improving material performance.Based on the worldwide research efforts in the last decade,the excellent mechanical properties and promising radiation and corrosion resistance of this group of materials have been demonstrated.High-entropy alloys with body-centered cubic(BCC)structures,especially refractory high-entropy alloys,are considered as promising materials for high-temperature applications in advanced nuclear reactors.However,the extreme reactor conditions including high temperature,high radiation damage,high stress,and complex corrosive environment require a comprehensive evaluation of the material properties for their actual service in nuclear reactors.This review summarizes the current progress on BCC high-entropy alloys from the aspects of neutron economy and activation,mechanical properties,high-temperature stability,radiation resistance,as well as corrosion resistance.Although the current development of BCC high-entropy alloys for nuclear applications is still at an early stage as the large design space of this group of alloys has not been fully explored,the current research findings provide a good basis for the understanding and prediction of material behaviors with different compositions and microstructures.Further in-depth understanding of the degradation mechanisms and characterization of material properties in response to conditions close to reactor environment are necessary.A critical down-selection of potential candidates is also crucial for further comprehensive evaluation and engineering validation.展开更多
In order to improve the discharge capacity and cyclic life of Mg-Co-based alloy, ternary Mg45M5Co50 （M=Pd, Zr） alloys were synthesized via mechanical alloying. TEM analysis demonstrates that these alloys all possess...In order to improve the discharge capacity and cyclic life of Mg-Co-based alloy, ternary Mg45M5Co50 （M=Pd, Zr） alloys were synthesized via mechanical alloying. TEM analysis demonstrates that these alloys all possess body-centered cubic （BCC） phase in nano-crystalline. Electrochemical experiments show that Mg45Zr5Co50 electrode exhibits the highest capacity （425 mA·h/g） among the Mg45M5Co50 （M=Mg, Pd, Zr） alloys. And Mg45Pd5Co50 electrode lifts not only the initial discharge capacity （379 mA·h/g）, but also the discharge kinetics, e.g., exchange current density and hydrogen diffusion ability from that of Mg50Co50. It could be concluded that the electrochemical performances were enhanced by substituting Zr and Pd for Mg in Mg-Co-based alloy.展开更多
GENERALLY the following two processes will take place simultaneously during hot deformation: one is work hardening caused by the increase of dislocation density on account of slip deforma-tion; the other is softening ...GENERALLY the following two processes will take place simultaneously during hot deformation: one is work hardening caused by the increase of dislocation density on account of slip deforma-tion; the other is softening caused by the process of recovery and recrystallization. The overalleffect of the development of the two contrary processes is influenced by deformation tempera-ture, rate and quantities. Among them temperature controls the rate of self-diffusion, whichaffects the proceeding of recovery and recrystallization as well. During recovery the dislocationdensity is mainly determined by deformation rate (ε) and strain quantities (ε).展开更多
晶体塑性理论是将晶体微观尺度的位错运动与宏观尺度的塑性形变相结合的重要理论,提供了在细观尺度内研究材料力学行为的有效方法。位错的密度变化对金属晶体的硬化行为有着重要的影响。该文在晶体塑性理论的基础上引入位错运动理论,建...晶体塑性理论是将晶体微观尺度的位错运动与宏观尺度的塑性形变相结合的重要理论,提供了在细观尺度内研究材料力学行为的有效方法。位错的密度变化对金属晶体的硬化行为有着重要的影响。该文在晶体塑性理论的基础上引入位错运动理论,建立基于位错密度的体心立方晶体(body center cubic,BCC)塑性本构模型,研究BCC的力学行为;并借助ABAQUS有限元软件,编写UMAT子程序,实现对BCC结构的铁单晶及多晶单轴拉伸试验的数值模拟。结果表明:该本构模型能有效地模拟铁单晶及多晶单轴拉伸的力学行为。展开更多
Fe_(72.4)Co_(13.9)Cr_(10.4)Mn_(2.7)B_(0.34)high entropy steel was prepared by magnetron sputtering.The alloy exhibits a high yield strength of 2.92±0.36 GPa while achieving appreciable plasticity of 13.7±1.9...Fe_(72.4)Co_(13.9)Cr_(10.4)Mn_(2.7)B_(0.34)high entropy steel was prepared by magnetron sputtering.The alloy exhibits a high yield strength of 2.92±0.36 GPa while achieving appreciable plasticity of 13.7±1.9%at the ultimate compressive strength(3.37±0.36 GPa).The distribution of iron and chromium shows an un-usual,characteristic spinodal-like pattern at the nanometer scale,where compositions of Fe and Cr show strong anticorrelation and vary by as much as 20 at.%.The high strength is largely attributable to the compositional modulations,combined with fine grains with body-centered cubic(BCC)crystal structure,as well as grain boundary segregation of interstitial boron.The impressive plasticity is accommodated by the formation and operation of multiplanar,multicharacter dislocation slips,mediated by coherent in-terfaces,and controlled by shear bandings.The excellent strength-ductility combination is thus enabled by a range of distinctive strengthening mechanisms,rendering the new alloy a potential candidate for safety-critical,load-bearing structural applications.展开更多
基金The project supported by National Natural Science Foundation of China(Grant No.19974027)the Foundation of Sichuan Provincial Education Committee(Grant No.01LB04)
文摘The formation mechanism for the body-centered cubic structure of cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy . The binding energy of with respect to was calculated to be 0.8857 a.u. This means that the cluster ofmay be formed in the body-centered cubic structure of .
基金Supported by National Natural Science Foundation of China(Grant No.51805032).
文摘Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.
基金the foundation of Westlake University for financial supportThe work at Zhejiang University was supported by the National Key Research and Development Program of China(2017YFA0303002)。
文摘The introduction of carbon interstitials into high-entropy alloys(HEAs)provides an effective way to improve their properties.However,all such HEA systems explored so far are limited to those with the face-centered-cubic(fcc)structure.Here we report the structural,mechanical and physical properties of the refractory(Nb_(0.375)Ta_(0.25)Mo_(0.125)W_(0.125)Re_(0.125))_(100−x)C_(x) HEAs over a wide x range of 0≤x≤20.It is found that,whereas the starting HEA(x=0)is composed of a major body-centered-cubic(bcc)phase with significant impurities,the bcc phase fraction increases with the C concentration and achieves almost 100%at x=20.Moreover,the increase of C content x results in an expansion of the bcc lattice,an enhancement of the microhardness,an increase in residual resistivity and a small variation of density of states at the Fermi level.All these features are consistent with the expectation that carbon atoms occupy the interstitial site.For x≥11.1,the X-ray photoelectron spectroscopy indicates the bond formation between the carbon and metal atoms,suggesting that some carbon atoms may also reside in the lattice site.In addition,a semiquantitative analysis shows that the enhanced mixing entropy caused by carbon addition plays a key role in stabilizing the(nearly)single solid-solution phase.Our study not only provides the first series of carbon interstitial HEAs with a bcc structure,but also helps to better understand the alloying behavior of carbon in refractory HEAs.
基金supported by the Key Project of the National Natural Science Foundation of China(11234011)
文摘Submicron and nanostructured body-centered cubic(BCC) metals exhibit unusual mechanical performance compared to their bulk coarse-grained counterparts, including high yield strength and outstanding ductility. These properties are important for their applications in micro-, nano-and even atomic-scale devices as well as for their usages as components for enhancing the performances of structural materials. One aspect of the unusual mechanical properties of small-sized BCC metals is closely related to their dimensional confinement. Decreasing the dimensions of single crystalline metals or the grain sizes of polycrystalline metals contributes significantly to the strengthening of the small-sized BCC metals.In the last decade, significant progress has been achieved in understanding the plasticity and deformation behaviors of small-sized BCC metals. This paper aims to provide a comprehensive review on the current understanding of size effects on the plasticity and deformation mechanisms of small-sized BCC metals. The techniques used for in situ characterization of the deformation behavior and mechanical properties of small-sized samples are also presented.
基金supported by the National Key Research and Development Program of China(Grant Nos.2019YFA0209900 and 2017YFB0304403)the National Natural Science Foundation of China(Grant No.12075179)+1 种基金the Nuclear Material Technology Innovation Center Project(Grant No.ICNM 2020 ZH05)the Continuous Basic Scientific Research Project(Grant No.WDJC-2019-10)
文摘High-entropy alloys greatly expand the alloy design range and offer new possibilities for improving material performance.Based on the worldwide research efforts in the last decade,the excellent mechanical properties and promising radiation and corrosion resistance of this group of materials have been demonstrated.High-entropy alloys with body-centered cubic(BCC)structures,especially refractory high-entropy alloys,are considered as promising materials for high-temperature applications in advanced nuclear reactors.However,the extreme reactor conditions including high temperature,high radiation damage,high stress,and complex corrosive environment require a comprehensive evaluation of the material properties for their actual service in nuclear reactors.This review summarizes the current progress on BCC high-entropy alloys from the aspects of neutron economy and activation,mechanical properties,high-temperature stability,radiation resistance,as well as corrosion resistance.Although the current development of BCC high-entropy alloys for nuclear applications is still at an early stage as the large design space of this group of alloys has not been fully explored,the current research findings provide a good basis for the understanding and prediction of material behaviors with different compositions and microstructures.Further in-depth understanding of the degradation mechanisms and characterization of material properties in response to conditions close to reactor environment are necessary.A critical down-selection of potential candidates is also crucial for further comprehensive evaluation and engineering validation.
基金Projects(51471087,61370042,21173041,11204031,11472080)supported by the National Natural Science Foundation of ChinaProject(13KJA430003)supported by the Jiangsu Higher Education Institutions of ChinaProject(BK20141336)supported by the Natural Science Foundation of Jiangsu Province,China
文摘In order to improve the discharge capacity and cyclic life of Mg-Co-based alloy, ternary Mg45M5Co50 （M=Pd, Zr） alloys were synthesized via mechanical alloying. TEM analysis demonstrates that these alloys all possess body-centered cubic （BCC） phase in nano-crystalline. Electrochemical experiments show that Mg45Zr5Co50 electrode exhibits the highest capacity （425 mA·h/g） among the Mg45M5Co50 （M=Mg, Pd, Zr） alloys. And Mg45Pd5Co50 electrode lifts not only the initial discharge capacity （379 mA·h/g）, but also the discharge kinetics, e.g., exchange current density and hydrogen diffusion ability from that of Mg50Co50. It could be concluded that the electrochemical performances were enhanced by substituting Zr and Pd for Mg in Mg-Co-based alloy.
文摘GENERALLY the following two processes will take place simultaneously during hot deformation: one is work hardening caused by the increase of dislocation density on account of slip deforma-tion; the other is softening caused by the process of recovery and recrystallization. The overalleffect of the development of the two contrary processes is influenced by deformation tempera-ture, rate and quantities. Among them temperature controls the rate of self-diffusion, whichaffects the proceeding of recovery and recrystallization as well. During recovery the dislocationdensity is mainly determined by deformation rate (ε) and strain quantities (ε).
文摘晶体塑性理论是将晶体微观尺度的位错运动与宏观尺度的塑性形变相结合的重要理论,提供了在细观尺度内研究材料力学行为的有效方法。位错的密度变化对金属晶体的硬化行为有着重要的影响。该文在晶体塑性理论的基础上引入位错运动理论,建立基于位错密度的体心立方晶体(body center cubic,BCC)塑性本构模型,研究BCC的力学行为;并借助ABAQUS有限元软件,编写UMAT子程序,实现对BCC结构的铁单晶及多晶单轴拉伸试验的数值模拟。结果表明:该本构模型能有效地模拟铁单晶及多晶单轴拉伸的力学行为。
基金supported by an Australian Research Council Discovery Project(Grant No.DP160104632)an Aus-tralian Government Research Training Program Scholarship.Y.J.Chen acknowledges the support provided by the Australian Re-search Council(Grant No.DE210101773).
文摘Fe_(72.4)Co_(13.9)Cr_(10.4)Mn_(2.7)B_(0.34)high entropy steel was prepared by magnetron sputtering.The alloy exhibits a high yield strength of 2.92±0.36 GPa while achieving appreciable plasticity of 13.7±1.9%at the ultimate compressive strength(3.37±0.36 GPa).The distribution of iron and chromium shows an un-usual,characteristic spinodal-like pattern at the nanometer scale,where compositions of Fe and Cr show strong anticorrelation and vary by as much as 20 at.%.The high strength is largely attributable to the compositional modulations,combined with fine grains with body-centered cubic(BCC)crystal structure,as well as grain boundary segregation of interstitial boron.The impressive plasticity is accommodated by the formation and operation of multiplanar,multicharacter dislocation slips,mediated by coherent in-terfaces,and controlled by shear bandings.The excellent strength-ductility combination is thus enabled by a range of distinctive strengthening mechanisms,rendering the new alloy a potential candidate for safety-critical,load-bearing structural applications.
