Effect of Modification with Different Contents of Sb and Sr on the Thermal Conductivity of Hypoeutectic Al-Si Alloy

Abstract

In this paper, the effects of size, morphology and distribution of eutectic silicon on the thermal conductivity of Al-8Si alloy modified by Sr (0.04, 0.08, 0.12 wt.%) and Sb (0.1, 0.3, 0.5 wt.%) elements with T6 heat treatment were investigated. The results show that the modified fibrous eutectic silicon has a significant capability of improvement of thermal conductivity, while the amount of the modifier has a relatively weak effect on thermal conductivity. After T6 treatment, the fracture or spheroidization of the flake eutectic silicon and the disappearance of clustering phenomenon could raise thermal conductivity, but the coarsening of fibrous eutectic silicon is inconducive to thermal conductivity. Finally, the effect of eutectic silicon on electron transport is analyzed in detail, which could provide a reference for enhancing the thermal (or electrical) conductivity of hypoeutectic Al-Si alloy through effective microstructure control.

Microstructure Evolution and Solidification Behavior of a Novel Semi-Solid Alloy Slurry Prepared by Vibrating Contraction Inclined Plate

“…This is closely associated with the morphology of eutectic Si phases [16,30]. In the A356 alloy, the formation of needle-shaped eutectic Si phases results in the decrease in mean free path and increase in electron scattering [30]. On the contrary, in the Al-Si-Mg-Cu-Fe-Sr alloy, eutectic Si phases with a short fibrous shape play an important role in increasing the electron channel, thereby decreasing the electron scattering and increasing the mean free path [16].…”

“…In addition to mechanical property, the Al-Si-Mg-Cu-Fe-Sr alloy has a higher thermal conductivity in comparison with the A356 alloy. This is closely associated with the morphology of eutectic Si phases [16,30]. In the A356 alloy, the formation of needle-shaped eutectic Si phases results in the decrease in mean free path and increase in electron scattering [30].…”

Effect of Cooling Rate and Modification by Strontium on the Thermal Conductivity of Al-8Si Alloy

“…Additionally, Al-Si alloys have a wide range of applications in industries such as automobiles, construction, and communications [5]. Especially since 5G base stations in communication began springing up all over the world recently, aluminum alloybased radiators are required to possess excellent thermal conductivity due to high power consumption and severe heat generation [6][7][8], along with enough mechanical properties and a light weight. Al-Si hypoeutectic alloys are a potential and powerful candidate for the requirement of radiators in 5G base stations.…”

“…For Al alloys, the mobility of electrons usually depends on the solid solution degree of solute elements in Al matrix, which has been investigated thoroughly in the past few decades [9,10]. However, when the chemical composition of solute elements is fixed for a given Al-Si hypoeutectic alloy, it is generally believed that the micro-structures of the alloy play a decisive role on the thermal conductivity, for example the morphology and size of the Si phase [7,11,12], and the density of defects such as grain boundary and phase boundary [10,13], which can be reflect by the secondary dendrite arm spacing (SDAS) in as-cast conditions.…”

“…The morphology of the eutectic silicon in Al-Si alloys can also be influenced by modification, leading to significant changes in the thermal conductivity. Guo et al [7] found that the eutectic Si changes from a long needle shape to a short rod shape due to the addition of Sr, which reduces the scattering effect of electrons and improves the thermal conductivity of the alloy. Wang et al [14] found that the addition of Sr can effectively increase the thermal conductivity of Al-Si hypoeutectic alloys, due to the formation of Al 2 Si 2 Sr phases on the surface of silicon.…”