チクソ及び金型鋳造したAA357アルミニウム合金の引張特性に及ぼす組織の影響 [in Japanese] Effects of Structures on Tensile Properties of AA357 Aluminum Alloy Produced by Thixo-and Permanent Mold Casting [in Japanese]
Access this Article
Search this Article
The effects of eutectic Si phase, Al-Fe system compounds and precipitates on the tensile properties of Al-7 mass % Si-0.5 mass % Mg 357 casting alloy produced by the thixocasting process were investigated. The tensile strength, 0.2 % proof stress and elongation of T6-treated thixocastings decrease from 360 MPa, 296 MPa and 13.6 % to 324 MPa, 274 MPa and 7.2 % with an increase in eutectic Si particle size from 2.3μm to 4.1μm, respectively. Relationships between tensile properties and eutectic Si particle size of thixocasting alloys were very similar with those of permanent mold castings. Two kinds of Al-Fe system compounds identified as β and π phases were observed at eutectic regions in both produced alloys. The needle-shaped precipitates were found lying along three  directions in the Al-matrix phase in thixoand permanent mold cast specimens aged at 433 K for 21.6 ks. Two types of precipitates with irregular and parallelogram network arrangement of bright dots in their cross-section were observed using high resolution transmission microscopy. These needle-shaped precipitates result in stronger Al-matrix in both alloys after T6-heat treatment. The morphology and size of precipitates of thixocast specimens were similar to those of permanent mold cast specimens. From results in this study, it was found that the tensile properties of the 357 thixocast alloy are mainly influenced by the size and shape of eutectic Si particles.
- Journal of Japan Foundry Engineering Society
Journal of Japan Foundry Engineering Society 74(5), 291-297, 2002-05-25
Japan Foundry Engineering Society