In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures...In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures and mechanical properties of the Al-5Mg-2Si alloy manufactured with different inclination angles(0°,30°,45°,60°and 90°)were reported and discussed.It is found that the“semicircular”melt pool(MP)in the load bearing face of 0°sample was eventually transformed into“stripe-like”MP in the 90°sample,accompanied by an increased fraction of melt pool boundaries(MPBs).Moreover,the microstructural analysis revealed that the columnar-to-equiaxed transition(CET)of theα-Al grains and eutectic Mg2Si was completed in the 90°sample,which were significantly refined with the average size of 10.6μm and 0.44μm,respectively.It is also found that the 90°sample exhibited good combination of strength and elongation(i.e.yield strength of 393 MPa,ultimate tensile strength of 483 MPa and elongation of 8.1%).The anisotropic mechanical properties were highly associated with the refined microstructures,thermal stress,and density of MPBs.Additionally,the CET driven by inclination angles was attributed to the variation of thermal conditions inside the local MPs.展开更多
We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and is...We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and isotropic linear hardening assumption.Further,four stress areas(σx,τx)are divided according to the characteristics of the final stress,and the plastic stress-strain relationship of twelve stress paths in different stress areas is derived.The"primary effect"of the stress path on plastic strain is demonstrated,namely,the plastic strain caused by the pre-loaded stress in path A(tensile stress is initially applied,followed by shear stress)is always greater than that caused by the post-loaded stress in path C(shear stress is initially applied,followed by tensile stress)irrespective of the value of final stress.The"recency effect"of the strain path on the stress is also established,which indicates that the stress caused by the post-loaded strain in path A is always greater than that caused by the pre-loaded strain in path C irrespective of the value of final strain.From the perspective of deformation,the"primary effect"of the stress path on the plastic strain and the"recency effect"of the strain path on the stress are unified.These effects are succinct and universal,and they provide useful insights on the plastic stress-strain relationship under different loading paths.Furthermore,they can serve as a useful reference for optimizing the processing technologies and construction procedures.展开更多
The origin of the Rayleigh scattering ring effect has been experimentally examined on a quantum dot/metal film system, in which CdTe quantum dots embedded in PVP are spincoated on a thin Au film. On the basis of the a...The origin of the Rayleigh scattering ring effect has been experimentally examined on a quantum dot/metal film system, in which CdTe quantum dots embedded in PVP are spincoated on a thin Au film. On the basis of the angle-dependent, optical measurements under different excitation schemes （i.e., wavelength and polarization）, we demonstrate that surface plasmon assisted directional radiation is responsible for such an effect. Moreover, an interesting phase-shift behavior is addressed.展开更多
Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage ex...Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage experi-ments were carried out. Horizontals flow are regarded as phreatic plan flows without penetration. Its seepage law sati-fies the Dupuit equation. With parallel lay seepage model,the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum. An unsaturated flow ap-peared in the vertical experiment,with a hydraulic gradient of 1. The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient. That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic co-efficient between 63 and 155,which is 25 to 100 times larger than that of a homogeneous body.展开更多
基金Project(52071343)supported by the National Natural Science Foundation of China。
文摘In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures and mechanical properties of the Al-5Mg-2Si alloy manufactured with different inclination angles(0°,30°,45°,60°and 90°)were reported and discussed.It is found that the“semicircular”melt pool(MP)in the load bearing face of 0°sample was eventually transformed into“stripe-like”MP in the 90°sample,accompanied by an increased fraction of melt pool boundaries(MPBs).Moreover,the microstructural analysis revealed that the columnar-to-equiaxed transition(CET)of theα-Al grains and eutectic Mg2Si was completed in the 90°sample,which were significantly refined with the average size of 10.6μm and 0.44μm,respectively.It is also found that the 90°sample exhibited good combination of strength and elongation(i.e.yield strength of 393 MPa,ultimate tensile strength of 483 MPa and elongation of 8.1%).The anisotropic mechanical properties were highly associated with the refined microstructures,thermal stress,and density of MPBs.Additionally,the CET driven by inclination angles was attributed to the variation of thermal conditions inside the local MPs.
基金Project(51979280)supported by the National Natural Science Foundation of ChinaProjects(2016M602972,2018M643852)supported by the Postdoctoral Science Foundation of China。
文摘We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and isotropic linear hardening assumption.Further,four stress areas(σx,τx)are divided according to the characteristics of the final stress,and the plastic stress-strain relationship of twelve stress paths in different stress areas is derived.The"primary effect"of the stress path on plastic strain is demonstrated,namely,the plastic strain caused by the pre-loaded stress in path A(tensile stress is initially applied,followed by shear stress)is always greater than that caused by the post-loaded stress in path C(shear stress is initially applied,followed by tensile stress)irrespective of the value of final stress.The"recency effect"of the strain path on the stress is also established,which indicates that the stress caused by the post-loaded strain in path A is always greater than that caused by the pre-loaded strain in path C irrespective of the value of final strain.From the perspective of deformation,the"primary effect"of the stress path on the plastic strain and the"recency effect"of the strain path on the stress are unified.These effects are succinct and universal,and they provide useful insights on the plastic stress-strain relationship under different loading paths.Furthermore,they can serve as a useful reference for optimizing the processing technologies and construction procedures.
基金This work was partially supported by the Ministry of Science and Technology of China （No.HH2060030013 and No.2016YFA0200602）, the National Natural Science Foundation of China （No.21573211 and No.21421063）, the Chinese Academy of Sciences （No.XDB01020000）, and the Fundamental Research Funds for the Central Universities （No.WK2340000063）.
文摘The origin of the Rayleigh scattering ring effect has been experimentally examined on a quantum dot/metal film system, in which CdTe quantum dots embedded in PVP are spincoated on a thin Au film. On the basis of the angle-dependent, optical measurements under different excitation schemes （i.e., wavelength and polarization）, we demonstrate that surface plasmon assisted directional radiation is responsible for such an effect. Moreover, an interesting phase-shift behavior is addressed.
基金Projects 2004CB619205 supported by the National Basic Research and Development Program of China50321402 by the National Science Fund for Distingui- shed Young Scholars of China50574099 by the National Natural Science Foundation of China
文摘Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage experi-ments were carried out. Horizontals flow are regarded as phreatic plan flows without penetration. Its seepage law sati-fies the Dupuit equation. With parallel lay seepage model,the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum. An unsaturated flow ap-peared in the vertical experiment,with a hydraulic gradient of 1. The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient. That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic co-efficient between 63 and 155,which is 25 to 100 times larger than that of a homogeneous body.
