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- Title
Development of Cast Hypereutectic Al-Si-X Alloys with Ultrafine–Si Phase Part 1: As-cast Structure Development.
- Authors
Guba, P.; Sokolowski, J.; Gesing, A.; Sobiesiak, A.; Conle, A.; Kasprzak, M.
- Abstract
A strontium-modified experimental Al20Si3Cu alloy was processed using the squeeze casting/high pressure die casting universal metallurgical simulator and analyzer (SC/HPDC UMSA) under impact and cyclic loading. Sample pressure and temperature vs. time were monitored during solidification, allowing thermal analysis to identify key solidification parameters. The application of pressure to the melt region improves the contact between the melt and the steel mold, which increases the initial melt cooling rate to ~100 °C/s and heat extraction by 40%. Metallographic analysis techniques including LOM, SEM/EDS, STEM/EDS were used to characterize the as-cast microstructure and microchemistry of selected samples. Metallographic data were collected from the polished and deep-etched surfaces as well as from STEM thin foils. This data allowed for the gathering of complementary information for determination of the relationship between the process and the thermal analysis parameters. The best processing parameters produced as-cast composite colonies that had a high fraction (~38 vol. %) dispersion of nanosized, individual, amorphous, Si-rich SiAl clusters and whiskers in a face-centered cubic (FCC) α-Al matrix. The clusters and whiskers had an average diameter of 220 nm with a standard deviation of 48 nm and whiskers were ~2 µm long. This nanocomposite structure was in the form of ~500 µm cauliflower-florets-shaped colonies of radial cells of ~30 µm in diameter that accounted for >85% of the material volume. We describe the process of formation of these newly discovered glassy SiAl nanophase clusters and whiskers in an FCC α-Al matrix. This ultrafine phase is a main, dominant feature of the as-cast ultrafine microstructure of Sr-modified, hypereutectic Al20Si3CuX alloy solidified under non-equilibrium conditions controlled by rapid heat extraction.
- Subjects
DIE-casting; SQUEEZE casting; ALUMINUM composites; FACE centered cubic structure; HYPEREUTECTIC alloys; CYCLIC loads; IMPACT loads
- Publication
International Journal of Metalcasting, 2023, Vol 17, Issue 3, p1535
- ISSN
1939-5981
- Publication type
Article
- DOI
10.1007/s40962-022-00888-5