Temporal evolution of the nanostructure of Al(Sc,Zr) alloys: Part I – Chemical compositions of Al₃(Sc_1−xZr_x) precipitates

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• 作者：Christian B. Fuller ; Joanne L. Murray and David N. Seidman
• 关键词：Al– ; Sc– ; Zr alloys ; Precipitation ; Microstructure ; High-resolution electron microscopy ; Three-dimensional atom-probe microscopy
• 刊名：Acta Materialia
• 出版年：2005
• 期刊代码：1_13596454
• 类别：ms
• 出版时间：2005
• 卷：53
• 期：20
• 页码：5401-5413
• 文件大小：807 K

摘要

Atom-probe tomography (APT) and high-resolution transmission electron microscopy are used to study the chemical composition and nanostructural temporal evolution of Al₃(Sc_1−xZr_x) precipitates in an Al–0.09 Sc–0.047 Zr at.%alloy aged at 300 °C. Concentration profiles, via APT, reveal that Sc and Zr partition to Al₃(Sc_1−xZr_x) precipitates and Zr segregates concomitantly to the α-Al/Al₃(Sc_1−xZr_x) interface. The Zr concentration in the precipitates increases with increasing aging time, reaching a maximum value of 1.5 at.%at 576 h. The relative Gibbsian interfacial excess cb46efcb27af894bf6f3"> of Zr, with respect to Al and Sc, reaches a maximum value of 1.24 ± 0.62 atoms nm⁻² after 2412 h. The temporal evolution of Al₃(Sc_1−xZr_x) precipitates is determined by measuring the time dependence of the depletion of the matrix supersaturation of Sc and Zr. The time dependency of the supersaturation of Zr does not follow the asymptotic t^−1/3 law while that of Sc does, indicating that a quasi-stationary state is not achieved for both Sc and Zr.