Paul Chao, Shanmukha Kiran Aramanda, Xianghui Xiao, Sabine Bottin-Rousseau, Silvère Akamatsu, Ashwin J. Shahani
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Unprecedented x-ray\nnano-imaging of the solid-liquid interface, and 3D characterization of the\ngrowth patterns, were made possible by a new Directional Solidification (DS)\nsetup at Brookhaven National Laboratory's NSLS-II. At low V, the leading tips\nof partly faceted Al3Ni crystals are observed to grow not far ahead of the Al\ngrowth front. Correlating in situ images and postmortem 3D tomographic\nreconstructions reveals that the presence of faceted and non-faceted regions of\nAl3Ni crystals in the solid is a direct consequence of coupling and decoupling\nduring DS, respectively. Upon increasing V , the lead distance of Al3Ni\nvanishes, and the shape of Al3Ni ceases to be governed by faceted growth. These\nobservations shed light on the basic mechanisms (faceted growth, diffusive\ncoupling, and the dynamics of trijunctions) governing the transition from\nfaceted to rod-like growth upon increasing V in the Al3Ni system, with broad\nimplications for a large class of irregular eutectics.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"9 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"From irregular to regular eutectic growth in the Al-Al3Ni system: in situ observations during directional solidification\",\"authors\":\"Paul Chao, Shanmukha Kiran Aramanda, Xianghui Xiao, Sabine Bottin-Rousseau, Silvère Akamatsu, Ashwin J. Shahani\",\"doi\":\"arxiv-2408.14346\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We investigate the irregular eutectic growth dynamics of the Al-Al3Ni alloy,\\nin which one of the solid phases (Al3Ni) grows faceted from the liquid.\\nLeveraging in situ optical microscopy and synchrotron transmission x-ray\\nmicroscopy, we address the question of the degree of coupling between Al and\\nAl3Ni at the growth front and that of the shape of the microstructures left\\nbehind in the bulk solid during directional solidification. Real-time optical\\nobservations bring evidence for a morphological transition from a\\neutectic-grain dependent, irregular eutectic growth at low solidification\\nvelocity V (typically 1 ${\\\\mu}ms^{-1}$), to a weakly anisotropic, regular\\ngrowth at higher V (reaching 10 ${\\\\mu}ms^{-1}$). Unprecedented x-ray\\nnano-imaging of the solid-liquid interface, and 3D characterization of the\\ngrowth patterns, were made possible by a new Directional Solidification (DS)\\nsetup at Brookhaven National Laboratory's NSLS-II. At low V, the leading tips\\nof partly faceted Al3Ni crystals are observed to grow not far ahead of the Al\\ngrowth front. Correlating in situ images and postmortem 3D tomographic\\nreconstructions reveals that the presence of faceted and non-faceted regions of\\nAl3Ni crystals in the solid is a direct consequence of coupling and decoupling\\nduring DS, respectively. Upon increasing V , the lead distance of Al3Ni\\nvanishes, and the shape of Al3Ni ceases to be governed by faceted growth. 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引用次数: 0
摘要
我们利用原位光学显微镜和同步辐射透射 X 射线显微镜,研究了 Al-Al3Ni 合金的不规则共晶生长动力学,其中一个固相(Al3Ni)从液体中长出切面。实时光学观测证明,在低凝固速度 V(通常为 1 ${\mu}ms^{-1}$)下,形态从依赖于共晶晶粒的不规则共晶生长过渡到高凝固速度 V(达到 10 ${\mu}ms^{-1}$)下的弱各向异性规则生长。布鲁克海文国家实验室 NSLS-II 的新型定向凝固(Directional Solidification,DS)装置使前所未有的固液界面 X 射线纳米成像和生长模式的三维表征成为可能。在低 V 值时,可以观察到部分刻面的 Al3Ni 晶体的前端在 Algrowth 前端不远处生长。将原位图像和死后三维断层扫描重建关联起来可以发现,Al3Ni 晶体在固体中的刻面和非刻面区域的存在分别是 DS 期间耦合和解耦的直接结果。当 V 值增大时,Al3Ni 的引线距离减小,Al3Ni 的形状不再受刻面生长的支配。这些观察结果揭示了 Al3Ni 体系在 V 值增大时从面状生长向棒状生长转变的基本机制(面状生长、扩散耦合和三结点动力学),对一大类不规则共晶具有广泛的影响。
From irregular to regular eutectic growth in the Al-Al3Ni system: in situ observations during directional solidification
We investigate the irregular eutectic growth dynamics of the Al-Al3Ni alloy,
in which one of the solid phases (Al3Ni) grows faceted from the liquid.
Leveraging in situ optical microscopy and synchrotron transmission x-ray
microscopy, we address the question of the degree of coupling between Al and
Al3Ni at the growth front and that of the shape of the microstructures left
behind in the bulk solid during directional solidification. Real-time optical
observations bring evidence for a morphological transition from a
eutectic-grain dependent, irregular eutectic growth at low solidification
velocity V (typically 1 ${\mu}ms^{-1}$), to a weakly anisotropic, regular
growth at higher V (reaching 10 ${\mu}ms^{-1}$). Unprecedented x-ray
nano-imaging of the solid-liquid interface, and 3D characterization of the
growth patterns, were made possible by a new Directional Solidification (DS)
setup at Brookhaven National Laboratory's NSLS-II. At low V, the leading tips
of partly faceted Al3Ni crystals are observed to grow not far ahead of the Al
growth front. Correlating in situ images and postmortem 3D tomographic
reconstructions reveals that the presence of faceted and non-faceted regions of
Al3Ni crystals in the solid is a direct consequence of coupling and decoupling
during DS, respectively. Upon increasing V , the lead distance of Al3Ni
vanishes, and the shape of Al3Ni ceases to be governed by faceted growth. These
observations shed light on the basic mechanisms (faceted growth, diffusive
coupling, and the dynamics of trijunctions) governing the transition from
faceted to rod-like growth upon increasing V in the Al3Ni system, with broad
implications for a large class of irregular eutectics.