과공정 Al-15wt.%Si 합금의 Primary Si 미세화와 인장 및 피로 특성에 미치는 EMS 공정의 영향

• Published in: 대한금속·재료학회지, 60(5) Vol. 60; no. 5; pp. 360 - 369
• Main Authors: 백민석, Min-Seok Baek, 강태훈, Tae-hoon Kang, 김종호, Jong-ho Kim, 박준표, Jun-pyo Park, 어광준, Kwangjun Euh
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 01.05.2022; 대한금속·재료학회
• Subjects: EMS (electromagnetic stirring); high-cycle fatigue; hyper-eutectic Al-Si alloy; primary Si refinement; tensile; 재료공학
• ISSN: 1738-8228; 2288-8241
• DOI: 10.3365/KJMM.2022.60.5.360

This study investigated the effect of the electromagnetic stirring (EMS) process on the microstructure and mechanical properties of hyper-eutectic Al-15 wt.%Si alloy. The tensile and high-cycle fatigue properties of the EMS Al-15wt.%Si alloy were examined and compared with conventional direct chill (DC) cast alloy. The initial microstructure of the as-cast DC alloy showed a coarse primary Si of 70 μm, in contrast to the size (40 μm) of the as-cast EMS alloy. The DC extruded alloy exhibited a massive primary Si size of 40~55 μm. In contrast, the EMS extruded alloy had a spherical primary Si with 30~40 μm sizes. The average grain sizes were measured to be 8.8 μm (EMS extruded alloy) and 11.4 μm (DC extruded alloy), respectively. The EMS process was confirmed to contribute to the refinement of the grain size and the primary Si size of the hyper-eutectic Al-Si alloy. The yield strengths at room temperature were measured to be 388.0 MPa (EMS extruded alloy) and 375.0 MPa (DC extruded alloy), and the tensile strengths were 426.0 MPa (EMS extruded alloy) and 412.4MPa (DC extruded alloy), respectively. The elongations of both alloys were similar at room temperature. The fatigue limit of the EMS extruded alloy (130 MPa) was higher than that of the DC extruded alloy (120 MPa). The EMS extruded alloy exhibited superior fatigue resistance compared to the DC extruded alloy, regardless of the cyclic stress condition. This study also discussed the potential value of the EMS process as a method for improving the properties of hyper-eutectic Al-Si alloy, as well as the deformation and fracture mechanisms of the EMS Al-15wt.%Si alloy. (Received 21 August, 2021; Accepted 11 January 2022)