Microstructural Evolution and Phase Transformation of Al–Mg–Si Alloy Containing 3% Li During Homogenization
The microstructural evolution and phase transformation of cast Al–1.5Mg–0.6Si–3Li (mass %) alloy during homogenization were investigated. The results show that severe dendritic segregation exists in the as-cast ingot. Mg and Si elements segregate at grain boundaries to form intermetallic Mg2Si phase. In addition, there also exists Li-containing phases, including T-Al2LiMg and δ-AlLi phase in the α-Al matrix. These Li-containing phases completely dissolve into the matrix and the segregation of dendrite is eliminated after homogenization at 570 °C for 24 h. During the homogenization, most of the Mg2Si phase at grain boundaries disappear, but AlLiSi ternary compounds precipitate and disperse at interior and boundary of grains because of the strong binding capacity between Li and Si element. The AlLiSi phase is detrimental to the properties of the alloy, therefore homogenization treatment may be not profitable for microstructural refinement of Al–1.5Mg–0.6Si–3Li alloy.
KeywordsAl–Mg–Si alloy Al–Li alloy Homogenization treatment Phase transformation
This study was supported by The National Key Research and Development Program of China (No. 2016YFB0300802).
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