Atom probe tomography study of an Fe25Ni25Co25Ti15Al10 high-entropy alloy fabricated by powder metallurgy
Atom probe tomography study of an Fe25Ni25Co25Ti15Al10 high-entropy alloy fabricated by powder metallurgy
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DOI：
10.1016/j.actamat.2019.08.047
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发表时间：
2019-10-15
期刊：
影响因子：
9.4
通讯作者：
Lavernia, Enrique J.
中科院分区：
文献类型：
--
作者：
Fu, Zhiqiang;Hoffman, Andrew;Lavernia, Enrique J.
利用透射电子显微镜（TEM）和原子探针层析成像（APT）研究了机械合金化（MA）和放电等离子烧结（SPS）制备的Fe 25 Ni 25 Co25 Ti 15 Al 10高熵合金（HEA）的显微组织和相组成。大块Fe 25 Ni 25 Co25 Ti 15 Al 10 HEA的特征在于2.52 GPa的高拉伸强度，并且包含次要的bcc相（类似于17.7体积%），以及包含分级纳米沉淀物的主要fcc相（类似于82.3体积%）。bcc相是含有大量Co、Ti和Fe的82型NiAl相;它还表现出平均直径为1.11 +/-0.33 nm的富Fe和Co纳米沉淀物。fcc相由γ Fe-（Co，Ni）基固溶体基体（A1）和共格的初级γ '（Ni，Co）（3）-（Ti，Al）基金属间沉淀物（L1（2））组成。发现Al结构的二次γ * 沉淀物共格地嵌入L12 γ-γ沉淀物中。我们提出，二次γ * 沉淀物的形成在很大程度上是由γ '沉淀物的独特化学组成驱动的，所述γ'沉淀物容纳大量的Fe、Al和Ti，再加上在我们的研究中使用的非平衡处理路线。令人惊讶的是，一种新型的Al-Ti-O氧化物是通过APT。Ti（C，N）化合物含有类似于9.19原子%的N和类似于12.27原子% Ni也被APT检测到，而不是简单的TiC。我们的分析表明，Al-Ti-O氧化物可能在MA过程中形成，而Ti（C，N）相在烧结过程中形成。此外，一个CALPHAD（计算相图）的方法被用来帮助了解潜在的相形成机制。Fe（25）N（12）5Co（25）Ti（15）Al（10）HEA具有2.52GPa的显著高强度，这支持了相形成机制对粉末冶金制备的HEA 5的力学性能起重要作用的假设。(C)2019 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
In this study, transmission electron microscopy (TEM) and atom probe tomography (APT) were utilized to investigate the microstructure and phases in an Fe25Ni25Co25Ti15Al10 high-entropy alloy (HEA) prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The bulk Fe25Ni25Co25Ti15Al10 HEA was characterized by a high tensile strength of 2.52 GPa and contained a minor bcc phase (similar to 17.7 vol%), together with a primary fcc phase (similar to 82.3 vol%) containing hierarchical nanoprecipitates. The bcc phase was a 82-type NiAI phase that contained substantial amounts of Co, Ti and Fe; it also exhibited Fe and Co rich nanoprecipitates with an average diameter of 1.11 +/- 0.33 nm. The fcc phase consisted of a gamma Fe-(Co,Ni)-based solid-solution matrix (A1), and coherent primary gamma' (Ni,Co)(3)-(Ti,Al)-based intermetallic precipitates (L1(2)). Al structured secondary y* precipitates were found coherently embedded in the L12 gamma-' precipitates. We propose that the formation of the secondary gamma* precipitates was largely driven by the unique chemical composition of the gamma' precipitates which accommodate substantial amounts of Fe, Al and Ti, coupled with the nonequilibrium processing route used in our studies. Surprisingly, a novel type of Al-Ti-O oxide was identified via APT. A Ti(C,N) compound containing similar to 9.19 at.% N and similar to 12.27 at.% Ni was also detected by APT, rather than a simple TiC. Our analysis suggests that the Al-Ti-O oxide likely formed during MA, whereas the Ti(C,N) phase formed during sintering. In addition, a CALPHAD (Calculation of Phase Diagrams) approach was utilized to assist in understanding the underlying phase formation mechanisms. The notable high strength of 2.52 GPa in the Fe(25)N(i2)5Co(25)Ti(15)Al(10) HEA support the hypothesis that phase formation mechanisms play an important role in the mechanical performance of HEA5 fabricated by powder metallurgy. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.