This paper irìvestigates the effect of three different Ni additions (0.5, 1 and 2 wt%) on the high-temperature tensile properties of the commercial purity unmodified A356 (Al-7 wt% Si-0.3 wt% Mg) aluminium foundry alloy As-cast and T6 heat-treated tensile samples, obtained by permanent mould casting, have been tested at 508 K (235 °C). Fracture profiles and surfaces have been observed via optical and scanning electron microscopy to analyse the failure mechanism. It was observed that Ni contents higher than 0.5 wt% cause a remarkable decrease in yield strength and ultimate tensile strength of the T6 heat-treated alloys, which therefore become comparable with the tensile properties of the corresponding as-cast alloys. According to microstructural observations, the early rupture of fragile Ni-rich intermetallic phases seems to govern the fracture process of these alloys, neutralising the positive effect of the heat treatment.
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Data di pubblicazione: | 2016 | |
Titolo: | Effect of Ni additions on A356 alloy's microstructure and high-temperature mechanical properties | |
Autori: | Casari, Daniele; Poli, Federico; Merlin, Mattia; Giovanni, Maria Teresa Di; Li, Yanjun; Di Sabatino, Marisa | |
Rivista: | LA METALLURGIA ITALIANA | |
Keywords: | Aluminium alloys; Casting; Nickel addition; Tensile properties; Electron microscopy | |
Abstract in inglese: | This paper irìvestigates the effect of three different Ni additions (0.5, 1 and 2 wt%) on the high-temperature tensile properties of the commercial purity unmodified A356 (Al-7 wt% Si-0.3 wt% Mg) aluminium foundry alloy As-cast and T6 heat-treated tensile samples, obtained by permanent mould casting, have been tested at 508 K (235 °C). Fracture profiles and surfaces have been observed via optical and scanning electron microscopy to analyse the failure mechanism. It was observed that Ni contents higher than 0.5 wt% cause a remarkable decrease in yield strength and ultimate tensile strength of the T6 heat-treated alloys, which therefore become comparable with the tensile properties of the corresponding as-cast alloys. According to microstructural observations, the early rupture of fragile Ni-rich intermetallic phases seems to govern the fracture process of these alloys, neutralising the positive effect of the heat treatment. | |
Handle: | http://hdl.handle.net/11392/2355384 | |
Appare nelle tipologie: | 03.1 Articolo su rivista |