과공정 Al- Si 합금의 반응고 교반시 초정 Si 형상에 미치는 교반조건 및 개량원소 첨가 영향

Effects of Stirring Condition and Refining Element Addition on the Primary Si Particle Morphology of Hypereutectic Al-Si Alloys Semi-Solid State Processing

Microstructural characteristics of semi-solid state processed hypereutectic Al-Si alloys have been investigated. Main concern of the present study is to investigate the effects of P and Sr addition on the size and morphology change of the primary Si particles. Refinement of the primary Si particles was observed with the addition of P and Sr at the early stage of semi-solid state processing, but such a refining effects became negligible resulting in Si particles with a near-spherical morphology with continuous stirring. This implies that the microstructural transformation mechanism became more dependent to stirring effects than to the alloying effects during semi-solid state processing. Brittle fracture and agglomeration were proposed as the mechanisms for microstructural alterations during semi-solid state processing.