High-temperature tensile properties of unmodified A356 alloy with and without the addition of Ni or V in traces (600 and 1000 ppm of Ni and V, respectively) were investigated by analyzing samples obtained from sand and permanent mold castings in the as-cast and T6 heat-treated conditions. Tensile tests were performed at 508 K (235 C) at a crosshead speed of 1 mm/min. In addition, samples were subjected to artificial aging at 508 K (235 C) for different times, and corresponding hardness curves were plotted. Microstructures and fracture surfaces, analyzed by FEG-SEM equipped with energy dispersive X-ray spectroscopy, showed that neither Ni nor V addition had a detrimental effect on high-temperature tensile properties. Aging curves showed a strong loss of hardness affecting the T6 class between 30-min and 1-h exposure time. After 6-h aging, no evidence of aging treatment persisted on hardness of the tested material. Hardness values did not reveal any significant difference between the reference alloy and the Ni- and V-containing alloys in both casting conditions, in complete analogy with the tensile properties. Unmodified eutectic silicon particles provided inhomogeneity in the a-Al matrix and acted as the principal source of stress concentration leading to fracture.

The influence of Ni and V trace elements on high-temperature tensile properties and aging of A356 aluminium foundry alloy

D. CASARI;MERLIN, Mattia;GARAGNANI, Gian Luca
Ultimo
2016

Abstract

High-temperature tensile properties of unmodified A356 alloy with and without the addition of Ni or V in traces (600 and 1000 ppm of Ni and V, respectively) were investigated by analyzing samples obtained from sand and permanent mold castings in the as-cast and T6 heat-treated conditions. Tensile tests were performed at 508 K (235 C) at a crosshead speed of 1 mm/min. In addition, samples were subjected to artificial aging at 508 K (235 C) for different times, and corresponding hardness curves were plotted. Microstructures and fracture surfaces, analyzed by FEG-SEM equipped with energy dispersive X-ray spectroscopy, showed that neither Ni nor V addition had a detrimental effect on high-temperature tensile properties. Aging curves showed a strong loss of hardness affecting the T6 class between 30-min and 1-h exposure time. After 6-h aging, no evidence of aging treatment persisted on hardness of the tested material. Hardness values did not reveal any significant difference between the reference alloy and the Ni- and V-containing alloys in both casting conditions, in complete analogy with the tensile properties. Unmodified eutectic silicon particles provided inhomogeneity in the a-Al matrix and acted as the principal source of stress concentration leading to fracture.
2016
DI GIOVANNI, M. T.; Cerri, E.; Casari, D.; Merlin, Mattia; Arnberg, L.; Garagnani, Gian Luca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2352205
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