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Yang Q.Q.,Tsinghua University | Liu Y.,Tsinghua University | Liu Y.,Key Laboratory for Advanced Materials Processing Technology Ministry of Education | Li Y.X.,Tsinghua University | Li Y.X.,Key Laboratory for Advanced Materials Processing Technology Ministry of Education
Materials Science Forum | Year: 2015

In this article, a three-dimensional time-dependent model describing the evolution of single pore during the solid/gas eutectic unidirectional solidification process (also called gasar process) was established. The mass transfer, bubble nucleation, pore growth and interruption were all considered in this model. The pore structure of lotus-type porous copper and aluminum were simulated under different solidification velocities. The results indicate that: coupled growth of both solid and gas phases can be achieved in a proper range of solidification velocities. The solidification velocity for Cu-H2 system is dozens of that for Al-H2 system when the pore diameter is similar to each other. The differences of the solute distribution coefficient (k0), diffusion coefficient (DL) and the constant of solubility of hydrogen (ξ(Tm)) in the melt are regarded as the main reasons of the big discrepancy of solidification velocity between Cu-H2 and Al-H2 systems. © (2015) Trans Tech Publications, Switzerland. Source


Wang N.-J.,Tsinghua University | Liu Y.,Tsinghua University | Liu Y.,Key Laboratory for Advanced Materials Processing Technology Ministry of Education | Zhang H.-W.,Tsinghua University | And 5 more authors.
China Foundry | Year: 2016

As an excellent giant-magnetostrictive material, Tb-Dy-Fe alloys (based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2 Laves compound) can be applied in many engineering fields, such as sonar transducer systems, sensors, and micro-actuators. However, the cost of the rare earth elements Tb and Dy is too high to be widely applied for the materials. Nowadays, there are two different ways to substitute for these alloying elements. One is to partially replace Tb or Dy by cheaper rare earth elements, such as Pr, Nd, Sm and Ho; and the other is to use non-rare earth elements, such as Co, Al, Mn, Si, Ce, B, Be and C, to substitute Fe to form single MgCu2-type Laves phase and a certain amount of Re-rich phase, which can reduce the brittleness and improve the corrosion resistance of the alloy. This paper systemically introduces the development, the fabrication methods and the corresponding preferred growth directions of Tb-Dy-Fe alloys. In addition, the effects of alloying elements and heat treatment on magnetostrictive and mechanical properties of Tb-Dy-Fe alloys are also reviewed, respectively. Finally, some possible applications of Tb-Dy-Fe alloys are presented. © 2016, Foundry Journal Agency. All rights reserved. Source

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