The microstructures of a thermally sprayed and heat treated Al–20 wt.%Sn–3 wt.%Si alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 403; no. 1; pp. 205 - 214
• Main Authors: Kong, C.J., Brown, P.D., Harris, S.J., McCartney, D.G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25-08-2005
• Subjects: Aluminium–silicon; Aluminium–tin; Microstructure; Rapid solidification; Thermal spraying; Aluminium–tin; Aluminium–silicon; Thermal spraying; Microstructure; Rapid solidification
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2005.04.051

High velocity oxy-fuel thermal spraying has been used to produce deposits of an Al–20
wt.%Sn–3
wt.%Si alloy approximately 300
μm thick on a steel substrate. The microstructures of the as-sprayed and annealed deposits were investigated by X-ray diffraction, scanning and transmission electron microscopy. The as-sprayed material comprised, mainly, elongated splats which were fully molten at the point of impact along with a small proportion of particles which had not been fully melted in the spray. The microstructure was composed of an α-Al matrix, a bimodal distribution of β-Sn and a small fraction of nanoscale Si precipitates. In partially molten splats, Sn formed as micron-sized particles. However, in fully molten splats the high cooling rate from the melt produced a dispersion of Sn particles, 20–100
nm in size, in the Al matrix. This is explained by the existence of a metastable liquid-phase miscibility gap in the Al–Sn phase diagram. Much of the Si, in the as-sprayed material, was retained in solid solution in the α-Al and the small amount of precipitate which formed appeared nano-sized. Following annealing at 300
°C for 1
h, the dispersed Sn particles coarsened and Si precipitated from the supersaturated α-Al as particles 50–200
nm in size.