Sr 개량처리된 사형주조 Al-7Si-0.35Mg 합금의 열처리에 따른 공정 Si상 변화거동 및 특성평가

• Published in: 한국주조공학회지 (주조) Vol. 38; no. 2; pp. 1 - 8
• Main Authors: 김명균, Myoung-gyun Kim, 황석민, Seok-min Hwang
• Format: Journal Article
• Language: Korean
• Published: 한국주조공학회 30.04.2018
• Subjects: Al-7Si-0.35Mg alloy; Mechanical properties; Modification; Sand casting; Solution treatment
• ISSN: 1598-706X

In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and α-Al phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.