Atomic-resolution evaluation of microsegregation and degree of atomic order at antiphase boundaries in Ni₅₀Mn₂₀In₃₀ Heusler alloy

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• 作者：K. Niitsu^a ; ^{koudai.niitsu@riken.jp" class="auth_mail" title="E-mail the corresponding author} ; K. Minakuchi^b ; X. Xu^b ; M. Nagasako^c ; I. Ohnuma^d ; T. Tanigaki^e ; Y. Murakami^a ; ^f ; D. Shindo^a ; ^g ; R. Kainuma^b
• 关键词：Heusler alloy ; High-angle annular dark-field ; Microsegregation ; Antiphase boundary ; Thermodynamics
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：122
• 期：Complete
• 页码：166-177
• 全文大小：4459 K

文摘

The atomic arrangement and microsegregation in the vicinity of thermally induced antiphase boundaries in a Ni₅₀Mn₂₀In₃₀ Heusler alloy are investigated through multislice simulations, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction pattern Rietveld analysis, energy-dispersive X-ray spectroscopy, and modified Bragg–Williams–Gorsky calculations. Intensity analysis of atomic-resolution HAADF-STEM images revealed that a 180° geometrical phase shift occurred across the antiphase boundaries, accompanied by a decay in the degree of atomic order and an enrichment of In. Energy-dispersive (X-ray) spectroscopy analysis revealed an In enrichment as high as 2.7 at.% at the center of the antiphase boundaries, comparable to that (1.0–1.8 at.%) suggested by the parallel tangent law for the Gibbs energy curves of the L2₁ and B2 phases using the modified Bragg–Williams–Gorsky calculation. This suggests that microsegregation occurs at the antiphase boundaries and can be understood basically within the framework of the local thermodynamic equilibrium.