In situ investigation of intermetallic compound formation during the solid Fe-liquid Al reaction by X-ray diffraction and tomography
Abstract
This study investigates the formation sequence and growth kinetics of intermetallic compounds (IMCs) during the reaction between liquid aluminum (Al) and solid iron (Fe), using for the first time both in situ synchrotron X-ray diffraction and tomography with samples designed to tailor the morphology of the reaction interface. Experimental samples comprised commercially pure mixtures of Al and Fe powders, as well as Al powders deposited onto Fe rods, annealed at temperatures ranging from 400 degrees C to 900 degrees C. Two primary IMC phases - Fe2Al5 and Fe4Al13 - were systematically observed during annealing, appearing simultaneously as soon as Al melted, with Fe2Al5 as the dominant phase, exhibiting its characteristic tongue-like morphology. A temperature ramp applied to the powder mixture further revealed the subsequent formation of FeAl, followed by FeAl2. The multisite and multidirectional reaction front of the powder mixture sample lead to very fast growth of the IMCs, consuming most of the reactants within a few tens of seconds. Conversely for the Al/Fe rod configuration (featuring a single reaction interface), the steady increase in IMC layer thickness was monitored in situ and confirmed to follow a volume-diffusion-controlled growth regime at 700 degrees C, with derived diffusion parameters: pre-exponential factor k0 = 8.43 10-2 m2 s-1 and activation energy Q = 187 kJ mol-1. However, at 770 degrees C and 830 degrees C, the kinetics deviated from this regime after an initial time delay, due to liquid Al dissolving the IMC layer. Beyond reducing layer thickness, this dissolution also induced Fe4Al13 precipitation within the Al matrix upon cooling. Tracking the displacement of the Fe/IMC and Al/IMC interfaces additionally demonstrated that Fe repels the IMC towards liquid Al, a mechanism proposed to minimize transformation-induced stress, scaling with the molar volume mismatch between Fe and Fe2Al5.
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BibTeX
@article{leflon2026situ,
title = {{In situ investigation of intermetallic compound formation during the solid Fe-liquid Al reaction by X-ray diffraction and tomography}},
author = {Benjamin Leflon and Thibaut Chaise and Christophe Le Bourlot and Nicolas Mary and Rafael Vargas and Wolfgang Ludwig and Shun Tokita and Kiyoaki T. Suzuki and Yutaka S. Sato and Sylvain Dancette},
journal = {Materials Characterization},
year = {2026},
month = sep,
doi = {10.1016/j.matchar.2026.116552},
url = {https://hal.science/hal-05673324v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - In situ investigation of intermetallic compound formation during the solid Fe-liquid Al reaction by X-ray diffraction and tomography
AU - Benjamin Leflon
AU - Thibaut Chaise
AU - Christophe Le Bourlot
AU - Nicolas Mary
AU - Rafael Vargas
AU - Wolfgang Ludwig
AU - Shun Tokita
AU - Kiyoaki T. Suzuki
AU - Yutaka S. Sato
AU - Sylvain Dancette
PY - 2026
DA - 2026/09/03
JO - Materials Characterization
DO - 10.1016/j.matchar.2026.116552
UR - https://hal.science/hal-05673324v1
AB - This study investigates the formation sequence and growth kinetics of intermetallic compounds (IMCs) during the reaction between liquid aluminum (Al) and solid iron (Fe), using for the first time both in situ synchrotron X-ray diffraction and tomography with samples designed to tailor the morphology of the reaction interface. Experimental samples comprised commercially pure mixtures of Al and Fe powders, as well as Al powders deposited onto Fe rods, annealed at temperatures ranging from 400 degrees C to 900 degrees C. Two primary IMC phases - Fe2Al5 and Fe4Al13 - were systematically observed during annealing, appearing simultaneously as soon as Al melted, with Fe2Al5 as the dominant phase, exhibiting its characteristic tongue-like morphology. A temperature ramp applied to the powder mixture further revealed the subsequent formation of FeAl, followed by FeAl2. The multisite and multidirectional reaction front of the powder mixture sample lead to very fast growth of the IMCs, consuming most of the reactants within a few tens of seconds. Conversely for the Al/Fe rod configuration (featuring a single reaction interface), the steady increase in IMC layer thickness was monitored in situ and confirmed to follow a volume-diffusion-controlled growth regime at 700 degrees C, with derived diffusion parameters: pre-exponential factor k0 = 8.43 10-2 m2 s-1 and activation energy Q = 187 kJ mol-1. However, at 770 degrees C and 830 degrees C, the kinetics deviated from this regime after an initial time delay, due to liquid Al dissolving the IMC layer. Beyond reducing layer thickness, this dissolution also induced Fe4Al13 precipitation within the Al matrix upon cooling. Tracking the displacement of the Fe/IMC and Al/IMC interfaces additionally demonstrated that Fe repels the IMC towards liquid Al, a mechanism proposed to minimize transformation-induced stress, scaling with the molar volume mismatch between Fe and Fe2Al5.
SN - 1044-5803
ER -