Structural Characterization and Precipitation in AlMg₅Si₂Mn Alloy

• Main Authors: Boyko, V.V., Link, T., Mykhalenkov, K.V.
• Format: Article
• Language: English
• Published: Інститут металофізики ім. Г.В. Курдюмова НАН України 2014
• Series: Металлофизика и новейшие технологии
• Subjects: Дефекты кристаллической решётки
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/107070

The as-cast structure of permanent mould and high-pressure die-castings of the AlMg₅Si₂Mn alloy is investigated by differential scanning calorimetry, microhardness measurements, transmission electron microscopy, and energy dispersive X-ray analysis. Inside the α-Al grains, the curved plate-like precipitates are detected for both alloys. Examination of these precipitates reveals a number of features, such as follow: (i) the composition of the precipitates is very close to the stoichiometric Mg₂Si compound; (ii) precipitates are aligned along dislocations; (iii) the precipitate density is much higher for the high-pressure die-castings, where the α-Al matrix contains more dislocations than in permanent mould castings; (vi) precipitates lie inside the α-Al grains, where they are randomly distributed. Precipitates are not observed among the Mg₂Si lamellas. Most likely, these precipitates are β′′ phase, and the mechanism of their formation is the heterogeneous nucleation on dislocations.