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pISSN : 1598-706X / eISSN : 2288-8381


(논문)연구논문

한국주조공학회지 (38권5호 095-102)

Effect of porosity on quality index of tensile property of A356 casting alloys

A356합금의 품질지수에 미치는 미소기공율의 영향

Choong Do Lee

Dept. of Metallurgical & Materials Engineering, Inha Technical College

DOI : http://dx.doi.org/10.7777/jkfs.2018.38.5.095

Abstract

The effects of Sr and (Ti-B) additives on the tensile properties of AC4A recycled (35% scrap content) aluminum alloys were investigated. An acicular morphology of the eutectic Si phase of as-cast specimens was converted to a fibrous morphology upon the addition of Sr. Moreover, morphology of the Sr modified eutectic Si phase became finer due to a T6 heat treatment. The grain size of the α-solid solution was decreased by the addition of (Ti-B) additives. Depending on the treatment conditions of the as- cast specimens, i.e., no addition, a Sr addition and a (Ti-B)+Sr addition, the tensile strength levels of the as-cast specimens were 182, 192, and 204㎫, respectively. The corresponding strengths of T6 heat-treated specimens were 293, 308, and 318㎫. Elongations of the as-cast specimens were 2.2, 3.1, and 5.6%, and the corresponding elongations of the T6 heat-treated specimens were 4.6, 6.1, and 7.6%. The percentage of the reduced section area in the tensile specimens was also increased by the Sr and (Ti-B) additives. Sr and (Ti-B) additives changed the microstructure and the distribution of defects in the castings, resulting in an improvement of the tensile properties of AC4A aluminum alloys. According to our test results, recycled (35% scrap content) AC4A aluminum alloy met all of the KS requirements of the tensile strength and elongation values of AC4A aluminum alloy except for the elongation value of the one specimen condition, in this case the as-cast no-addition condition.

Keywords

Tensile property, Aluminium alloy, Porosity, Quality index