Effects of Si and Sr elements on solidification microstructure and thermal conductivity of Al-Si-based alloys.

Effects of Si and Sr on solidification microstructure and thermal conductivity of Al-Si binary alloys and Al-9Si-Sr ternary were investigated, respectively, with a special focus on the relationship between solidification microstructure and thermal conductivity. It was found that (i) in Al-Si binary alloys, with increasing Si content, α-Al grain size increases and then decreases when Si content is over 7 wt%, while the percentage of eutectic Si continuously increases, which significantly decreases the thermal conductivity and electrical conductivity, and (ii) in Al-9Si-Sr ternary alloys, the presence of Sr has no significant effect on α-Al grain, but effectively modifies eutectic Si and significantly improves the thermal and electrical conductivity. On this basis, two theoretical calculation models [the Maxwell model and the Hashin-Shtrikman (H-S) model] were used to elucidate the relationship between solidification microstructure and thermal conductivity. Compared with the Maxwell model, the H-S model fits better with the measured values. The obtained results are very helpful to the precise composition control during alloy design and recycling of Al-Si-based alloys with the aim to further improve the thermal conductivity of Al-Si-based alloys. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10853-022-07045-7.