The effect of La and Ce on the microstructure and properties of cast Al Si alloys with high thermal conductivity
Journal
Materials Characterization
ISSN
1044-5803
Date Issued
2026-04
Author(s)
Fubiao Ge
Yezeng He
Xuping Zhang
Reza Behmadi
Siyi Sun
Chuansheng Zhu
Akbar Hojjati-Najafabadi
Fang He
Abstract
The study focused on the impacts of lanthanum and cerium on the microstructure, mechanical properties, and thermal conductivity of Al-6 wt%Si-0.5 wt%Cu-0.6 wt%Fe alloys.
Accordingly, it was determined that the synergistic addition of La and Ce significantly refined the alloy structure. In Al-6Si-0.6Fe-0.5Cu-0.3(La + Ce), the SDAS decreased to 13.1 μm and eutectic Si transformed from coarse plates into fine particles; the size and aspect ratio of Si were reduced by 90.13% and 81.48%, respectively. Meanwhile, the length of Fe-rich phases was shortened by 57.51%.
Consequently, the alloy exhibited enhanced properties compared with the rare earth-free alloy, such as thermal conductivity up to 159.68 W/(m·K), ultimate tensile strength of 231.3 MPa, and elongation up to 6.89%, corresponding to enhancements of 13.79%, 24.96%, and 118.73%, respectively.
The alloy prepared by high-pressure die casting exhibits excellent properties, with thermal conductivity reaching 175.58 W/(m·K), tensile strength of 240.6 MPa, and elongation after fracture of 7.62%.
Furthermore, largescale fully formed LED lamp heat sinks have been successfully prepared from this alloy using HPDC; in this way, its engineering applicability has been confirmed. These enhancements are ascribed to eutectic Si refinement, which reduces electron scattering, and rare-earth enrichment at Fe-rich phase interfaces, suppressing their growth and strengthening the matrix.
The findings provide an insight into the key mechanism of the rare earth synergy in enhancement of thermo-mechanical properties in AlSi alloys, opening a new way in material design for effective thermal management applications.
Accordingly, it was determined that the synergistic addition of La and Ce significantly refined the alloy structure. In Al-6Si-0.6Fe-0.5Cu-0.3(La + Ce), the SDAS decreased to 13.1 μm and eutectic Si transformed from coarse plates into fine particles; the size and aspect ratio of Si were reduced by 90.13% and 81.48%, respectively. Meanwhile, the length of Fe-rich phases was shortened by 57.51%.
Consequently, the alloy exhibited enhanced properties compared with the rare earth-free alloy, such as thermal conductivity up to 159.68 W/(m·K), ultimate tensile strength of 231.3 MPa, and elongation up to 6.89%, corresponding to enhancements of 13.79%, 24.96%, and 118.73%, respectively.
The alloy prepared by high-pressure die casting exhibits excellent properties, with thermal conductivity reaching 175.58 W/(m·K), tensile strength of 240.6 MPa, and elongation after fracture of 7.62%.
Furthermore, largescale fully formed LED lamp heat sinks have been successfully prepared from this alloy using HPDC; in this way, its engineering applicability has been confirmed. These enhancements are ascribed to eutectic Si refinement, which reduces electron scattering, and rare-earth enrichment at Fe-rich phase interfaces, suppressing their growth and strengthening the matrix.
The findings provide an insight into the key mechanism of the rare earth synergy in enhancement of thermo-mechanical properties in AlSi alloys, opening a new way in material design for effective thermal management applications.