Al-6Si-2Cu 합금의 미세조직 및 기계적 특성에 미치는 주조 공정과 고용화 열처리의 영향

Abstract

Effects of casting process and solid silution treatment on microstructure and mechanical properties of Al-6Si-2Cu alloy were investigated. The test specimens were prepared by gravity casting and die-casting process. Solution heat treatments and shot peening were applied to as-cast and die-cast alloy to improve mechanical properties. The microstructure of as-cast and die-cast specimens presents a typical dendrite structure, having a secondary dendrite arm spacing (SDAS) of 37 um and 18 um, respectively. In addition to the Al matrix, a large amount of coarse eutectic Si, Al2Cu intermetallic phase and Fe-rich phases were identified. After solution heat treatment, single-step solution heat treatments considerably improved the spheroidization of the eutectic Si phase. Two-step solution treatments enhanced more spheroidization. The mechanical properties of the two-step solution heat treated alloy showed improved mechanical properties. In case of shot peening, surface grains and eutectic Si particles are refiend by plastic deformation and the surface hardness of shot peening alloy shows higher value than unpeened alloy. Consequentially, the microstructural and mechanical characteristics of the Al alloy have been successfully characterized and are available for use with the basic data for the development of lightweight automotive parts.