Transactions of Nonferrous Metals Society of China
JOURNAL OF RAILWAY SCIENCE AND ENGINEERING
|Vol. 18 No. 1 January 2008|
（State Key Laboratory for Fabrication and Processing of Non-ferrous Metals,General Research Institute for Non-ferrous Metals, Beijing 100088, China）
Abstract:The microstructure of an AA 7B04 alloy in the form of plate was investigated using differential scanning calorimetry (DSC) and TEM analysis technologies. Tensile properties and electrical conductivity of AA 7B04 under various heat treatment conditions were also presented. The results reveal that peak-aged microstructure contains GP zones and η′ precipitates predominantly. After retrogressing and reaging(RRA), the η′ and η precipitates disperse in the alloy matrix, and the η precipitates distribute coarsely and sparsely, decorating the grain boundaries, together with precipitate free zones(PFZs) around them. It is also shown that selecting of suitable heat treatments can provide optimal precipitates in matrix and at grain boundaries, which gives rise to a combination of high strength and stress corrosion cracking(SCC) resistance in such materials.
Key words: Al alloy; 7B04 aluminum alloy microstructure; TEM; DSC; properties