A new insight into heterogeneous nucleation mechanism of Al by non-stoichiometric TiCx
A new insight into heterogeneous nucleation mechanism of Al by non-stoichiometric TiCx
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非化学计量 TiCx 对 Al 异相成核机制的新见解
DOI：
10.1016/j.actamat.2022.117977
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发表时间：
2022-05-07
期刊：
影响因子：
9.4
通讯作者：
Liu, Xiangfa
中科院分区：
文献类型：
--
作者：
Yang, Huabing;Qian, Zhao;Liu, Xiangfa
自20世纪50年代以来，Al-Ti-C中间合金一直被认为是一种有效的铝合金细化剂。然而，到目前为止，其细化机理仍未完全阐明。在这里，我们通过Cs校正的电子显微镜和理论计算相结合的方法系统地研究了这种机制。首先，确定Al/TiCx形核界面为“类似界面过渡层的Al类似TiCx”的三明治状结构，其取向关系为[011]Al//[011]TiCx和(1(1)在Bar1)[011]Al面上倾斜21度至(1(1))在Bar1)[011]TiCx面上，有利于消除Al和TiCx之间的晶格常数失配。界面过渡层由Al和Ti原子组成，对减少(1(3)在Bar3)[011]Al和(1(1)在Bar1)[011]TiCx上的原子排列失配起到至关重要的作用，从而促进Al形核。其次，与通常认为的直接与铝熔体反应不同，含x<；0.92的TiCx实际上在孕育(720℃)后首先向铝熔体释放钛原子，有助于形成含钛的界面过渡层。另一方面，TiCx析出后，TiCx中的C/Ti比增大，反而降低了析钛能力，导致晶粒细化逐渐衰退。本研究对Al-Ti-C精炼铝的细化机理有了新的认识，并为开发含TiC(x-)的高效细化剂奠定了基础。(C)2022材料学报，爱思唯尔有限公司出版。版权所有。
Al-Ti-C master alloy has been known as an efficient grain refiner for a series of Al alloys since 1950s. However, the grain refinement mechanism is still not fully elucidated up to now. Herein, we systematically investigate this mechanism by combining Cs-corrected transmission electron microscopy and theoretical calculations. First, the Al/TiCx nucleation interface is determined to be a "Al similar to Interfacial transition layer similar to TiCx " sandwich-like structure, with the orientation relationship of [011]Al//[011]TiCx and (1 (1) over bar1)[011]Al plane inclined 21 degrees to (1 (1) over bar1)[011]TiCx plane that is beneficial to eliminate the lattice constant misfit between Al and TiCx. The interfacial transition layer, consisting of Al and Ti atoms, play a crucial role in reducing atomic arrangement mismatch between (1 (3) over bar3)[011]Al and (1 (1) over bar1)[011]TiCx, thus promoting Al nucleation. Second, rather than directly reacting with Al melt as conventionally reckoned, TiCx with x < 0.92 actually releases Ti atoms to Al melt first after inoculation (720 degrees C), contributing to the formation of the Ti-containing interfacial transition layer. On the other hand, after Ti releasing, C/Ti ratio in TiCx is increased, which inversely decreases the Ti-releasing capability and leads to grain refinement fading gradually. This study sheds new light on the grain refinement mechanism in Al-Ti-C-refined Al and should build up the foundation for developing high-efficiency TiC(x-)containing grain refiners.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.