Controllable 3D morphology and growth mechanism of quasicrystalline phase in directionally solidified Al–Mn–Be alloy
Controllable 3D morphology and growth mechanism of quasicrystalline phase in directionally solidified Al–Mn–Be alloy
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DOI：
10.1557/jmr.2014.287
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发表时间：
2014-11
影响因子：
2.7
通讯作者：
Huijun Kang;Tongmin Wang;Yiping Lu;J. Jie;Xinzhong Li;Yan-Qing Su;Jingjie Guo
中科院分区：
文献类型：
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作者：
Huijun Kang;Tongmin Wang;Yiping Lu;J. Jie;Xinzhong Li;Yan-Qing Su;Jingjie Guo
研究了定向凝固Al-6 Mn-2.5Be（wt%）合金中初生I相颗粒在较宽生长速率范围内（100-1500 µm/s）的三维形貌演化和生长机制。在相对较低的生长速率（100-600 µm/s）下，I相颗粒表现出具有强各向异性的小面生长，形成具有二十面体形态对称性的分级花状聚集体，由几个连接的不规则多面体或五边形十二面体组成。在更高的增长率下（例如，1000 µm/s）时，I相的界面沿五角十二面体的边缘和拐角沿着变得不稳定，从而引起生长扰动。相应地，随着增长率的增加，从多面增长到非多面增长的转变发生了。生长速率的进一步提高导致I相柱状枝晶沿3重轴沿着择优生长。花状聚集体的构型可以用完美的和细长的五角十二面体的几何模型来充分说明。基于对I相颗粒三维形貌演化的清晰理解，提出了花状聚集体的生长机制。
Three-dimensional (3D) morphological evolution and growth mechanisms of primary I-phase particles have been investigated in directionally solidified Al–6Mn–2.5Be (wt%) alloy at a wide range of growth rates (100–1500 µm/s). At relatively low growth rates (100–600 µm/s), the I-phase particles exhibit faceted growth with strong anisotropy, forming a hierarchical flower-like aggregate with icosahedral morphological symmetry composed of several attached irregular polyhedrons or pentagonal dodecahedrons. At higher growth rates (e.g., 1000 µm/s), the interface of the I-phases becomes unstable along the edges and corners of the pentagonal dodecahedron, thereby arousing growth perturbations. Correspondingly, a transition from faceted to nonfaceted growth occurs with increasing growth rate. Further increase of the growth rate leads to the formation of I-phase columnar dendrites’ preferential growth along the 3-fold axis. The configurations of the flower-like aggregates can be adequately illustrated by a geometrical model in terms of the perfect and elongated pentagonal dodecahedrons. A growth mechanism for the flower-like aggregates has been proposed based on the clear understanding of the 3D morphological evolution of the I-phase particles.