Twinned dendrite growth in binary aluminum alloys
Twinned dendrite growth in binary aluminum alloys
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DOI：
10.1016/j.actamat.2008.07.046
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发表时间：
2008-11
期刊：
影响因子：
9.4
通讯作者：
M. A. Salgado-Ordorica;M. Rappaz
中科院分区：
文献类型：
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作者：
M. A. Salgado-Ordorica;M. Rappaz
在相同的热条件下，即G = 100 Kcm-1，v = 100 Kcm-1，熔体中有轻微的自然对流，在定向凝固的试样中研究了二元Al-Zn，Al-Mg，Al-Cu和Al-Ni合金中孪晶枝晶（羽毛状晶粒）的形成。溶质元素的性质和含量的影响已被发现是不太重要的比以前报道的，因为羽毛状晶粒形成在所有四种合金，无论合金元素是六方密堆积（锌和镁）或面心立方与高（镍）或低（铜）堆垛层错能。详细的分析证实，在所有四种情况下，孪晶树突沿沿着110 μ m方向生长，具有由多达六至九个臂组成的复杂分支形态。令人惊讶的是，在高Zn或Mg组成下，规则枝晶沿沿着110 μ m而不是沿100 μ m生长[冈萨雷斯F，Rappaz M. Metall Trans A 2006; 37：2797. [1]]不能形成孪晶枝晶。从孪晶枝晶的生长动力学优势和枝晶尖端形状两方面来看，一些实验证据似乎与亨利[亨利S.洛桑联邦理工学院博士论文，1999年。[21]]，至少在本工作中研究的溶质组成。
The formation of twinned dendrites (feathery grains) in binary Al–Zn, Al–Mg, Al–Cu and Al–Ni alloys has been studied in specimens directionally solidified under identical thermal conditions, i.e. G≈100Kcm−1, v≈1mms−1, and with slight natural convection in the melt. The influence of the solute element nature and content has been found to be of less importance than previously reported since feathery grains were formed in all four alloys, regardless whether the alloying elements are hexagonal close packed (Zn and Mg) or face-centered cubic with a high (Ni) or low (Cu) stacking fault energy. A detailed analysis confirmed that twinned dendrites grow along 〈110〉 directions in all four cases, with a complex branch morphology made of up to six to nine arms. Surprisingly, at high Zn or Mg compositions for which regular dendrites grow along 〈110〉 instead of 〈100〉, [Gonzales F, Rappaz M. Metall Trans A 2006; 37: 2797. [1]] no twinned dendrites could be formed. In terms of both the growth kinetics advantage of twinned dendrites over regular ones and the associated tip shape, some experimental evidence seems to contradict the doublon conjecture suggested by Henry [Henry S. PhD thesis, Ecole Polytechnique Fédéral de Lausanne, 1999. [21]], at least for the solute compositions studied in the present work.