To investigate the diffusion reaction between Ti/Al solid diffusion couple, Ti/Al alternate foils formed by hot pressing were annealed at 525, 550, 575 and 600 °C for time ranging from 1 to 40 h. The experimental...To investigate the diffusion reaction between Ti/Al solid diffusion couple, Ti/Al alternate foils formed by hot pressing were annealed at 525, 550, 575 and 600 °C for time ranging from 1 to 40 h. The experimental results show that TiAl3 was the only observed phase at Ti/Al interface. The interface thermodynamics favored the preferential formation of TiAl3 in Ti/Al couple. The growth of TiAl3 layer occurred mainly towards Al foil side and exhibited a parabolic law. Using the interdiffusion coefficients calculated based on the contribution of grain boundary diffusion, the growth of TiAl3 was simulated numerically with the finite difference method, and the simulated results were in good agreement with the experimental ones.展开更多
Polycrystalline bulk Ti3AlC2 material with high purity and density was fabricated by hot pressing from the powder mixture with the starting stoichiometric mole ratios of 2.0TiC/ 1.0Ti/ 1.1A1/ 0.1Si at 1 300-1 500℃. X...Polycrystalline bulk Ti3AlC2 material with high purity and density was fabricated by hot pressing from the powder mixture with the starting stoichiometric mole ratios of 2.0TiC/ 1.0Ti/ 1.1A1/ 0.1Si at 1 300-1 500℃. X-ray diffraction patterns and scanning electron microscopy photographs of the fully dense samples indicate that the proper addition of silicon is favorable to the formation of Ti3AlC2, consequently results in high purity of the prepared samples. The Ti3AlC2 hot pressed at 1 300℃and 1 400℃is in plane-shape with sizes of 6-8μm and 15-20μm in the elongated dimension, respectively. The purities of samples are measured by the K-value method, and the contents of TiC are given by a linear equation.展开更多
In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a...In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a three-way pipe capsule for offshore engineering under mechanical vibration conditions.The effects of vibration parameters—such as the vibration time,vibration frequency,vibration amplitude,rolling friction coefficient,sliding friction coefficient,recovery coefficient,and other particle properties—on the filling density were analyzed.The results showed that the packing density in the three-way capsule could be increased considerably using a vibration frequency of 40 Hz and a vibration amplitude of 2.5 mm.The contact form between particles in the vibration-assisted mold-filling process was determined and the particle velocity field,compression force,and coordination number under a single harmonic vibration period were analyzed.The real-time motion of the particles at the micro level was visualized,and the mechanism of the mechanical vibration effect on mold filling and densification was explored.The distribution and evolution of the coordination number indicated that the distribution of the filling density was uneven,and that the change in the coordination number of particles at the bottom exhibited no major response to the vibration.展开更多
基金Project (50771041) supported by the National Natural Science Foundation of ChinaProject (05-0350) supported by the New Century Excellent Talents in University, China
文摘To investigate the diffusion reaction between Ti/Al solid diffusion couple, Ti/Al alternate foils formed by hot pressing were annealed at 525, 550, 575 and 600 °C for time ranging from 1 to 40 h. The experimental results show that TiAl3 was the only observed phase at Ti/Al interface. The interface thermodynamics favored the preferential formation of TiAl3 in Ti/Al couple. The growth of TiAl3 layer occurred mainly towards Al foil side and exhibited a parabolic law. Using the interdiffusion coefficients calculated based on the contribution of grain boundary diffusion, the growth of TiAl3 was simulated numerically with the finite difference method, and the simulated results were in good agreement with the experimental ones.
文摘Polycrystalline bulk Ti3AlC2 material with high purity and density was fabricated by hot pressing from the powder mixture with the starting stoichiometric mole ratios of 2.0TiC/ 1.0Ti/ 1.1A1/ 0.1Si at 1 300-1 500℃. X-ray diffraction patterns and scanning electron microscopy photographs of the fully dense samples indicate that the proper addition of silicon is favorable to the formation of Ti3AlC2, consequently results in high purity of the prepared samples. The Ti3AlC2 hot pressed at 1 300℃and 1 400℃is in plane-shape with sizes of 6-8μm and 15-20μm in the elongated dimension, respectively. The purities of samples are measured by the K-value method, and the contents of TiC are given by a linear equation.
基金financial support of Beijing Nova Program(grant No.2022139).
文摘In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a three-way pipe capsule for offshore engineering under mechanical vibration conditions.The effects of vibration parameters—such as the vibration time,vibration frequency,vibration amplitude,rolling friction coefficient,sliding friction coefficient,recovery coefficient,and other particle properties—on the filling density were analyzed.The results showed that the packing density in the three-way capsule could be increased considerably using a vibration frequency of 40 Hz and a vibration amplitude of 2.5 mm.The contact form between particles in the vibration-assisted mold-filling process was determined and the particle velocity field,compression force,and coordination number under a single harmonic vibration period were analyzed.The real-time motion of the particles at the micro level was visualized,and the mechanism of the mechanical vibration effect on mold filling and densification was explored.The distribution and evolution of the coordination number indicated that the distribution of the filling density was uneven,and that the change in the coordination number of particles at the bottom exhibited no major response to the vibration.
