Coarse columnar β grains result in anisotropic mechanical properties in Ti alloys deposited by additive manufacturing. This study reports that Ti-6Al-4V alloy fabricated by coaxial electron beam wire feeding additive...Coarse columnar β grains result in anisotropic mechanical properties in Ti alloys deposited by additive manufacturing. This study reports that Ti-6Al-4V alloy fabricated by coaxial electron beam wire feeding additive manufacturing presents a weak anisotropy, high strength and ductility. The superior tensile property arises from a microstructure with fine equiaxed β grains(EGβ), discontinuous grain boundary α phase and short intragranular α lamellae. A large region of fine EGβ arises from a special combination of the temperature gradient and solidification rate, and attractive α morphology is caused by solid phase transformations during interpass thermal cycling and post heat treatments.展开更多
It is widely reported that CALPHAD is an extrapolation method when the thermodynamic properties of a multicomponent system are approximated by its subsystems.In this work the meaning of the words extrapolation and int...It is widely reported that CALPHAD is an extrapolation method when the thermodynamic properties of a multicomponent system are approximated by its subsystems.In this work the meaning of the words extrapolation and interpolation is discussed in context of the CALPHAD method.When assessing the properties in binary and ternary systems,extrapolation method is indeed often used.However,after assessment,the Gibbs energies are in fact interpolated from the lower order systems into the higher order systems in the compositional space.The metastable melting temperatures of bcc and hep in Re-W and the liquid miscibility gap in Mg-Zr system are predicted to illustrate the difference between interpolation and extrapolation.展开更多
The pronounced brittleness of hard Laves phase intermetallics is detrimental to their tribological properties at room temperature.In this study,we utilized a heterogeneous structure to engineer an ultrastrong dual-pha...The pronounced brittleness of hard Laves phase intermetallics is detrimental to their tribological properties at room temperature.In this study,we utilized a heterogeneous structure to engineer an ultrastrong dual-phase(Laves+B2)AlCoFeNiNb high-entropy alloy that exhibits a low wear rate(3.82×10-6 mm3/(N·m))at room temperature.This wear resistance in the ball-on-disc sliding friction test with the counterpart of Al2O3 balls stems from the activated deformation ability in the ultrafine Laves lamellae under heterogeneous interface constraints.Furthermore,as tribological stress intensifies,the surface deformation mechanism transitions from dislocation slip on the basal and pyramidal planes to a unique combination of local shear and grain rotation within the Laves phase.Our study illuminates fresh perspectives for mitigating the embrittling effect of Laves phase intermetallics under tribological loading and for the development of wear-resistant materials.展开更多
基金supported by the internal funding source from University of Shanghai for Science and Technology.
文摘Coarse columnar β grains result in anisotropic mechanical properties in Ti alloys deposited by additive manufacturing. This study reports that Ti-6Al-4V alloy fabricated by coaxial electron beam wire feeding additive manufacturing presents a weak anisotropy, high strength and ductility. The superior tensile property arises from a microstructure with fine equiaxed β grains(EGβ), discontinuous grain boundary α phase and short intragranular α lamellae. A large region of fine EGβ arises from a special combination of the temperature gradient and solidification rate, and attractive α morphology is caused by solid phase transformations during interpass thermal cycling and post heat treatments.
基金financial support from the National Natural Science Foundation of China (Nos. 51671118 and 51871143)Young Elite Scientists Sponsorship Program by CAST (No. 2017QNRC001)+2 种基金the “Chenguang” project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (No. 17CG42)Science and Technology Committee of Shanghai (No. 16520721800)Aeronautical Science Fund ¨Integrated computational research of the additive manufacturing for ultra-high strength Ti alloys¨(No. 2017ZF25022)
文摘It is widely reported that CALPHAD is an extrapolation method when the thermodynamic properties of a multicomponent system are approximated by its subsystems.In this work the meaning of the words extrapolation and interpolation is discussed in context of the CALPHAD method.When assessing the properties in binary and ternary systems,extrapolation method is indeed often used.However,after assessment,the Gibbs energies are in fact interpolated from the lower order systems into the higher order systems in the compositional space.The metastable melting temperatures of bcc and hep in Re-W and the liquid miscibility gap in Mg-Zr system are predicted to illustrate the difference between interpolation and extrapolation.
基金supports from the National Natural Science Foundation of China(Grant nos.52371068,51931003,52301157,and 52001165)Natural Science Foundation of Jiangsu Province,China(Grant nos.BK20200475 and BK20220965)+2 种基金Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant no.2022ZB251)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant no.XDB0470101)the Fundamental Research Funds for the Central Universities(Grant nos.30921011215 and 30922010401).
文摘The pronounced brittleness of hard Laves phase intermetallics is detrimental to their tribological properties at room temperature.In this study,we utilized a heterogeneous structure to engineer an ultrastrong dual-phase(Laves+B2)AlCoFeNiNb high-entropy alloy that exhibits a low wear rate(3.82×10-6 mm3/(N·m))at room temperature.This wear resistance in the ball-on-disc sliding friction test with the counterpart of Al2O3 balls stems from the activated deformation ability in the ultrafine Laves lamellae under heterogeneous interface constraints.Furthermore,as tribological stress intensifies,the surface deformation mechanism transitions from dislocation slip on the basal and pyramidal planes to a unique combination of local shear and grain rotation within the Laves phase.Our study illuminates fresh perspectives for mitigating the embrittling effect of Laves phase intermetallics under tribological loading and for the development of wear-resistant materials.
