Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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Transactions of Nonferrous Metals Society of China

Vol. 26    No. 3    March 2016

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Microstructural evolution of Mg, Ag andZn micro-alloyed Al-Cu-Li alloy during homogenization
Qing LIU1, Rui-hua ZHU1, Jin-feng LI1, Yong-lai CHEN2, Xu-hu ZHANG2, Long ZHANG1, Zi-qiao ZHENG1

1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Aerospace Research Institute of Materials and Processing Technology, Beijing 100076, China

Abstract:The microstructural evolution of a Mg, Ag and Zn micro-alloyed Al-3.8Cu-1.28Li (mass fraction, %) alloy ingot during two-step homogenization was examined in detail by optical microscopy (OM), differential scanning calorimetry (DSC), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) methods. The results show that severe dendritic segregation exists in the as-cast ingot. There are many secondary phases, including TB (Al7Cu4Li), θ(Al2Cu), R(Al5CuLi3) and S(Al2CuMg) phases, and a small amount of (Mg+Ag+Zn)-containing and AlCuFeMn phases. The fractions of intermetallic phases decrease sharply after 2 h of second-step homogenization. By prolonging the second-step homogenization time, the TB,θ, R, S and (Mg+Ag+Zn)-containing phases completely dissolve into the matrix. The dendritic segregation is eliminated, and the homogenization kinetics can be described by a constitutive equation in exponential function. However, it seems that the AlCuFeMn phase is separated into Al7Cu2Fe and AlCuMn phases, and the size of Al7Cu2Fe phase exhibits nearly no change when the second-step homogenization time is longer than 2 h.


Key words: Al-Cu-Li alloy; homogenization; microstructural evolution; Al7Cu2Fe; AlCuMn

ISSN 1004-0609
CN 43-1238/TG

ISSN 1003-6326
CN 43-1239/TG

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