Influence of Microstructures on Mechanical Properties of Al-Si-Cu-Mg Cast Alloys = Al-Si-Cu-Mg 주조합금의 기계적 성질에 미치는 현미경 조직의 영향

다국어 초록 (Multilingual Abstract)

A commercial Al-Si-Cu base alloy (JIS AC4B) and the similar compositions of pure alloys with 0 to 0.7%Fe were solidified at the cooling rate of 2.7 to 14.4K/s. Tensile tests and quantitative microstructure analysis were performed on the as cast specimens and T_6specimens. Tensile strength (бB) increased as the microstructure became finer. бB rose linearly with decreasing of secondary dendrite arm spacing(DAS) of primary α , while the modification of eutectic Si with Sr had a smaller effect. The crack propagated along dendrite arms and the fracture surface exhibited a structure whose coarseness was close to DAS. Fe-rich intermetallic compounds took the acicular and chinese script type shapes. Higher cooling rate and more Sr addition promoted the crystallization of chinese type one. The Fe-rich compounds decreased the elongation, though they tended to raise the yield strength. TEM analysis revealed that the aging process was influenced by eutectic Si and minor elements, however the these phenomena may have little influence on tensile properties.

목차 (Table of Contents)

• Ⅰ. INTRODUCTION
• Ⅱ. EXPERIMENTAL PROCEDURES
• Ⅲ. RESULT AND DISCUSSION
• 1. Influence of Sr addition and cooling rate on microstructures
• 2. Influences of Sr and cooling rate on tensile properties
• 3. Fracture appearances of tensile specimens
• Ⅳ. CONCLUSIONS