Influence of cooling rate on the microstructure and ageing behavior of as-cast Al–Sc–Zr alloy

Al–0.3Sc–0.15Zr alloy was cast using copper die, insulated alumina mould, and conventional investment shell mould to obtain a wide range of cooling rates. A novel method of quenching the investment shell mould along with the liquid metal in oil was also used which resulted in a significant increase...

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Bibliographic Details
Published in:Journal of materials processing technology 2010-11, Vol.210 (15), p.2135-2141
Main Authors: Lohar, A.K., Mondal, B.N., Panigrahi, S.C.
Format: Article
Language:English
Subjects:
Aging
Aluminum base alloys
Al–Sc–Zr alloy
As-cast ageing
Cooling rate
Financing
Molds
Precipitates
Precipitation
Shell moulds
Solidification rate
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Summary:Al–0.3Sc–0.15Zr alloy was cast using copper die, insulated alumina mould, and conventional investment shell mould to obtain a wide range of cooling rates. A novel method of quenching the investment shell mould along with the liquid metal in oil was also used which resulted in a significant increase in the cooling rate. The order in increasing average cooling rate is 0.16, 0.78, 1.28, 5.93, 7.69 °C/s. The as-cast samples were aged isothermally at 300 °C and various temperatures for 2 h. Slow cooled samples (in alumina-insulated mould) showed the presence of as-cast primary precipitates as well as rod shaped discontinuous precipitates with high density of interfacial dislocation. The amount of as-cast precipitates decreased with increase in the cooling rate. These as-cast precipitates grew at the expense of Sc in solid solution reducing the number of precipitates formed during ageing process. This results in lower increment in hardness on ageing.
ISSN:0924-0136
DOI:10.1016/j.jmatprotec.2010.07.035