Microstructural evolution in directionally solidified Al-Cu-Mg ternary eutectic

[摘要] This work seeks to increase our fundamental understanding of microstructure evolution and pattern formation in multi-component, multi-phase metallic materials during freezing. The solidification behavior of three-phase Al-Cu-Mg eutectic was investigated via directional solidification using a Bridgman furnace with varied thermal gradients (G = 3.0-14.4 K/mm) and velocities (0.625-4.0 mu m/s). Precise quantification of the resulting microstructures was carried out using phase fraction, eutectic spacing, axis ratio, phase size, and nearest neighbor measurements. The results of the qualitative and quantitative assessments of the evolving structure showed that the modified two-lamellar, one-rod microstructure previously presented for this system breaks down below a critical velocity. The effect of velocity, gradient and composition on the stability of the three-phase coupled growth is considered, and results are compared to thermodynamically predicted values. Unlike in the related eutectic system of Al-Ag-Cu, thermal gradient was found to have no measurable effect on either eutectic spacing or pattern, results which were further supported with inferential statistical tests (ANOVA and Tukey's HSD). (c) 2021 Elsevier B.V. All rights reserved.

[发布日期] 2021-11-25

[关键词] Directional solidification;Ternary eutectic;Al-Cu-Mg;Microstructure;Statistical test