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


(논문)연구논문

한국주조공학회지 (17권6호 560-568)

Decomposition Behavior of Secondary Solidification Phase During Heat Treatment of Squeeze Cast Al-Cu-Si-Mg

용탕단조 Al-Cu-Si-Mg합금의 열처리시 제2응고상의 분해거동

Yu-Chan Kim, Do-Hyang Kim*, Yo-Sub Han**, Ho-In Lee**

Yonsei University, *Jointly appointed at the center for Advanced Aerospace Materials, **Korea Institute of Science and Technology

Abstract

The dissolution behavior of secondary solidification phases in squeeze cast Al-3.9wt%Cu-1.5wt%Si- 1.owt%Mg has been studied using a combination of optical microscope, image analyzer, scanning electron microscope(SEM), energy dispersive spectrometer(EDS), X-ray diffractome-ter(XRD) and differential thermal analyzer (DTA). Special emphasis was placed on the investigation of the effects of the nonequilibrium heat treatment on the dissolution of the second solidification phases. As- cast microstructure consisted of primary solidification product of on-Al and secondary solidification products of A1-,.Cu, Mg2Si and Al2CuMg. Equilibrium and non-equilibrium solution treatments were carried out at the temperatures of 495°C, 502°C and 515°C for 3 to 5 hours. The amount of the dissolved secondary phases increased with increasing solution treatment temperature, for example, area fractions of Al2Cu, Mg2Si and Al;._CuMg were approximately 0%, 1.6% and 4.2% after solution treatment at 495°C for Shours, and were approximately 0%, 0.36% and 2% after solution treatment at 515°C for Shours. The best combination of tensile properties was obtained when the as~cast alloy was solution treated at 515°C for 3hours followed by aging at 180°C for 10 hours. Detailed DTA and TEM study showed that the strengthening behavior during aging was due to enhanced precipitation of the platelet type fine θ phase.

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