Hardness and microstructure of sterling silver cast by sloped cooling plate method
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Publication Details
Author list: Chomsaeng N., Poolthong N.
Publication year: 2017
Journal: Chiang Mai University Journal of Natural Sciences (1685-1994)
Volume number: 16
Issue number: 4
Start page: 255
End page: 262
Number of pages: 8
ISSN: 1685-1994
Languages: English-Great Britain (EN-GB)
Abstract
Semi-solid casting was introduced to improve the mechanical properties of sterling silver by sloped cooling plate technique. Ag alloys (93.5 wt%) were cast from an induction furnace at 1,000°C onto a sloped cooling plate. The pouring angles and distances were 30-60 degree and 200-250 mm, respectively. Effects of pouring angles and casting distances on hardness and microstructure of the sterling silver were investigated. Then, the solution was treated, followed by quenching and artificial aging. The specimens were checked with Vickers microhardness tester, light microscope, and scanning electron microscope (SEM). Hardness of the as-cast sample from the semi-solid process was 63-78 HV. The 60-minute aged sample that was cast at a 30° angle and 250 mm distance obtained the maximum hardness of 148.5 HV. The microstructure of the as-cast sample consisted primarily of α-phase and eutectic structure. A spheroidal and short dendrite structure was formed in the as-cast sample. After aging, precipitation occurred substantially within the α-phase. SEM images revealed that the aged sample with the highest hardness contained Cu-rich and Ag-rich precipitates in the α-phase.
Keywords
Semi-solid casting, Sterling silver
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