Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 749, Issue -, Pages 487-502Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2018.03.178
Keywords
Al-Si alloy; Intermetallics; Corrosion; Rheo-HPDC; Thermal conductivity
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Funding
- National Key Research and Development Program of China [2016YFB0300901]
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The microstructures, mechanical properties, thermal conductivities, and corrosion behavior of novel high-thermal-conductivity hypoeutectic Al-Si alloys, prepared by rheological high-pressure die-casting (Rheo-HPDC) and HPDC, were investigated and compared. The microstructure of the Rheo-HPDC alloy, including the primary alpha-Al (alpha(1)), secondary alpha-Al (alpha(2)-Al), beta-Al5FeSi, and Si phases, was significantly more refined than that of the HPDC alloy. Compared to the HPDC alloy, the Rheo-HPDC alloy exhibited superior mechanical properties and thermal conductivity, and its ultimate tensile strength (UTS), yield strength (YS), elongation, hardness, and thermal conductivity were improved by 27%, 21%, 72%, 10% and 8%, respectively. Pitting corrosion of the Rheo-HPDC alloy was observed to originate at the interfaces between the Fe-rich intermetallics and the alpha(2)-Al particles. Corrosion was observed to propagate in the eutectic areas upon prolonged immersion in 3.5 wt% NaCl solution. Electrochemical testing, scanning Kelvin probe (SKP) measurements, and corrosion-morphology analyses reveal that the Rheo-HPDC alloy has better corrosion resistance, primarily due to the decrease in the potential difference between the Fe-rich intermetallics and the matrix, the refinement of the eutectic Si and intermetallics, and the decrease in the areal ratio of eutectic Si to alpha(2)-Al. (C) 2018 Elsevier B.V. All rights reserved.
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