Effect of B addition on the formation of Fe-rich phases in Al-Si-Fe alloys

作者：Song, Dongfu^*; Zhao, Yuliang^*; Jia, Yiwang; Huang, Guangyao; Zhang, Zhibo; Zhou, Nan; Li, Xintao; Zheng, Kaihong; Fu, Yanan; Zhang, Weiwen^*

来源：Journal of Alloys and Compounds, 2023, 930: 167426.

DOI：10.1016/j.jallcom.2022.167426

• Fe -rich phase
• B addition
• Al -Si alloy
• Solidification
• Synchrotron X-ray radiography
• First -principles calculations

Boron (B) is an effective grain refiner in Al-Si alloys, but the mechanism responsible for the effect of B on the formation and growth of Fe-rich phases is still in debate. In this paper, we used in-situ synchrotron X-ray radiography, combined with optical microscopy, scanning electron microscopy, thermodynamics and first -principles calculations, to study the influence of B on the nucleation and growth of Fe-rich phases in Al-7Si-xFe (x = 1.2-3.0) alloys. The results showed that B had an excellent influence on the grain refinement of Al-7Si-1.2Fe alloys, but it had no obvious effect on the morphology and distribution of Fe-rich phases due to the eutectic reaction to form Al-AlB2. B had a certain refining effect on primary Fe-rich phases in Al-Si-Fe alloys with high Fe content (>= 2.36 wt. %), but it cannot completely inhibit the formation of these plate-like Fe-rich phases. The in-situ synchrotron X-ray radiography results showed that the addition of B significantly reduced the formation temperature of primary Fe-rich phases. First-principles calculations showed that the adsorption energy of B on the nucleation sites , e.g., <<-Al2O3 (0001), was significantly higher than that of Fe, which inhibited the nucleation of the primary Fe-rich phase above the Al-AlB2 eutectic temperature and promoted its undercooling of nucleation. Furthermore, many <<-Al nuclei formed during the transition to the Al-AlB2 eutectic; their subsequent growth hindered the development of the primary Fe-rich phase. The results of this study provide insights for designing new recycled Al-Si alloys and fundamental knowledge of Fe-rich phase modification by B addition.

• 单位
  中国科学院; 东莞理工学院