Improvement in mechanical, thermal conductivity and corrosion performances of a new high-thermally conductive Al-Si-Fe alloy through a novel R-HPDC process

Abstract A low-cost, new casting Sr-modified Al-7.5Si-0.8Fe alloy with high-thermal conductivity was prepared into large thin-wall heat-dissipating shells for 5G communication base stations using a traditional high pressure die-casting (HPDC) process and a rheological HPDC (R-HPDC) technique. Their microstructure, tensile property, hardness, thermal conductivity, and corrosion behavior were analyzed. The R-HPDC Al-7.5Si-0.8Fe alloy shows a refined microstructure in terms of α1-Al particles, α2-Al grains, fibrous β-Al5FeSi, and granular eutectic silicons when compared to traditional HPDC alloys. The R-HPDC alloy has a thermal conductivity, elongation-to-failure value, ultimate tensile strength, yield strength, and Vickers hardness of 186 W/(m.K), 12.4 %, 235 MPa, 114 MPa, and 70 HV, respectively. These values are respectively 6 %, 91 %, 22 %, 14 %, and 11 % higher than those reported for conventional HPDC alloys. Moreover, the R-HPDC Al-Si-Fe alloy shows a superior corrosion resistance in comparison to HPDC alloys. This observation is supported by scanning Kelvin probe (SKP) measurements and electrochemical tests. The improved performances arise mostly from the refinement of the iron-rich intermetallics (β-Al5FeSi) and eutectic silicons, the increase in the area proportion of α2-Al grains relative to eutectic silicon, and the reduction in the potential difference between the aluminum matrices and the iron-rich intermetallics.