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The effect of boron on the refinement of microstructure in cast cobalt alloys

Published online by Cambridge University Press:  02 March 2011

Michael J. Bermingham*
Affiliation:
Defence Material Technology Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and Centre for Advanced Materials Processing and Manufacturing, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia
Stuart D. McDonald
Affiliation:
Defence Material Technology Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and CAST Cooperative Research Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia
David H. StJohn
Affiliation:
Defence Material Technology Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and CAST Cooperative Research Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and Centre for Advanced Materials Processing and Manufacturing, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia
Matthew S. Dargusch
Affiliation:
Defence Material Technology Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and CAST Cooperative Research Centre, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia; and Centre for Advanced Materials Processing and Manufacturing, School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072 Australia
*
a)Address all correspondence to this author. e-mail: m.bermingham@uq.edu.au
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Abstract

Controlling the grain size and morphology of cast cobalt-based components is important for optimizing a component’s in-service properties. This work investigates the role of boron on the grain size of binary cobalt–boron alloys by application of contemporary grain refinement theory. Boron solute is found to refine the width of the columnar grains but fails to promote the columnar to equiaxed transition. The lack of equiaxed grains is attributed to the thermal solidification conditions and a lack of potent nucleant particles. The refinement of the columnar grains with boron solute may be due to a growth restriction mechanism.

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Articles
Copyright
Copyright © Materials Research Society 2011

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