Atomic-scale observation and analysis of chemical ordering in M3B2 and M5B3 borides

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	Atomic-scale observation and analysis of chemical ordering in M3B2 and M5B3 borides
	Hu, XB; Niu, HY; Ma, XL; Oganov, AR; Fisher, CAJ; Sheng, NC; Liu, JD; Jin, T; Sun, XF; Liu, JF
刊名	ACTA MATERIALIA
	2018-05-01
卷号	149 页码:274-284
关键词	Crystal-structure Prediction Total-energy Calculations Nickel-base Superalloys Ni-based Superalloy X-ray Spectroscopy Wave Basis-set Probe Tomography Polycrystalline Superalloy Grain-boundary Resolution
ISSN号	1359-6454
英文摘要	Secondary phases precipitated in diffusion affected zones (DAZs) of a transient liquid phase (Tip) bonded Ni-based superalloy have a large impact on materials properties. Here we report an atomic-scale analysis of the crystal structures and elemental distributions within DAZ precipitates in a TLP-bonded single-crystal superalloy using a range of electron microscopy techniques. The predominant precipitate phases are found to be M3B2- and M5B3-type borides, where M is a mixture of transition metal elements. Atomically-resolved energy-dispersive X-ray spectroscopy in an aberration-corrected scanning transmission electron microscope (STEM) enabled the distributions of metal atoms within the precipitates to be determined. The observation that different metals occupy preferred sites within the crystals indicates that these phases are not uniform solid solutions, but instead are chemically ordered. Both borides contain two distinct metal lattice sites such that the phases can be described as L2SB2 and L4SB3, where L and S are elements with larger (e.g., W, Mo) and smaller (e.g., Cr, Co, Ni) atomic numbers, respectively. Ordering of W and Cr is found to be particularly strong. A systematic search for stable phases within the chemical space of the W-Cr-B ternary system using the crystal structure prediction (CSP) program USPEX provided further insights into the nature of the observed chemical ordering. This combination of STEM and CSP techniques provides a direct and robust way of determining chemical features and local structures of multicomponent phases with atomic resolution even when particle sizes are too small for analysis using conventional methods. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.; Secondary phases precipitated in diffusion affected zones (DAZs) of a transient liquid phase (Tip) bonded Ni-based superalloy have a large impact on materials properties. Here we report an atomic-scale analysis of the crystal structures and elemental distributions within DAZ precipitates in a TLP-bonded single-crystal superalloy using a range of electron microscopy techniques. The predominant precipitate phases are found to be M3B2- and M5B3-type borides, where M is a mixture of transition metal elements. Atomically-resolved energy-dispersive X-ray spectroscopy in an aberration-corrected scanning transmission electron microscope (STEM) enabled the distributions of metal atoms within the precipitates to be determined. The observation that different metals occupy preferred sites within the crystals indicates that these phases are not uniform solid solutions, but instead are chemically ordered. Both borides contain two distinct metal lattice sites such that the phases can be described as L2SB2 and L4SB3, where L and S are elements with larger (e.g., W, Mo) and smaller (e.g., Cr, Co, Ni) atomic numbers, respectively. Ordering of W and Cr is found to be particularly strong. A systematic search for stable phases within the chemical space of the W-Cr-B ternary system using the crystal structure prediction (CSP) program USPEX provided further insights into the nature of the observed chemical ordering. This combination of STEM and CSP techniques provides a direct and robust way of determining chemical features and local structures of multicomponent phases with atomic resolution even when particle sizes are too small for analysis using conventional methods. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
学科主题	Materials Science, Multidisciplinary ; Metallurgy & Metallurgical Engineering
语种	英语
资助机构	National Natural Science Foundation of China [11327901]; Russian Science Foundation [16-13-10459]; MEXT, Japan [12024046]
公开日期	2018-06-05
内容类型	期刊论文
源URL	[http://ir.imr.ac.cn/handle/321006/79326]
专题	金属研究所_中国科学院金属研究所
通讯作者	Ma, XL (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Liaoning, Peoples R China.; Ikuhara, Y (reprint author), Japan Fine Ceram Ctr, Nanostruct Res Lab, Nagoya, Aichi 4568587, Japan.; Oganov, AR (reprint author), SUNY Stony Brook, Inst Adv Computat Sci, Ctr Mat By Design, Dept Geosci, Stony Brook, NY 11794 USA.
推荐引用方式 GB/T 7714	Hu, XB,Niu, HY,Ma, XL,et al. Atomic-scale observation and analysis of chemical ordering in M3B2 and M5B3 borides[J]. ACTA MATERIALIA,2018,149:274-284.
APA	Hu, XB.,Niu, HY.,Ma, XL.,Oganov, AR.,Fisher, CAJ.,...&Oganov, AR .(2018).Atomic-scale observation and analysis of chemical ordering in M3B2 and M5B3 borides.ACTA MATERIALIA,149,274-284.
MLA	Hu, XB,et al."Atomic-scale observation and analysis of chemical ordering in M3B2 and M5B3 borides".ACTA MATERIALIA 149(2018):274-284.