과공정 Al-15wt.%Si 압출재와 회주철의미세조직 및 엔진 오일 환경에서의 마모 특성

초록

This study investigated the microstructure and wear properties of extruded hyper-eutectic Al-Si (15wt.%) alloy in an engine oil environment. The wear mechanism of the material was also analyzed and compared to conventional gray cast iron. In microstructural observation results of Al-15wt.%Si alloy, primary Si phase (45.3㎛) and eutectic Si phase (3.1㎛) were found in the matrix, and the precipitations of Mg2Si(β’), Al2Cu(θ’) and Al6(Mn,Fe) were also detected. In the case of gray cast iron, ferrite and pearlite were observed. It was also observed that flake graphite (20-130㎛) were randomly distributed. Wear rates were lower in the Al-Si alloy as compared to those of gray cast iron in all load conditions, confirming the outstanding wear resistance of Al-15wt.%Si alloy in engine oil environment. In the 4 kgf condition, the wear rate of gray cast iron was 6.0ⅹ10-5 and that of Al-Si measured 0.8ⅹ10-5. The microstructures after wear of the two materials were analyzed using scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The primary Si and eutectic Si of Al-Si alloy effectively mitigated the abrasive wear, and the Al matrix effectively endured to accept a significant amount of plastic deformation caused by wear.

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