한국주조공학회

In this study, we focused on the correlation between the solidification structure, heat t 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 so solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the h heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 a alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially sph spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eu eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the e elongation. This is supported by the fracture surface in the tensile test.

Al-7Si-0.35Mg alloy, Modification, Sand casting, Solution treatment, Mechanical properties