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Materials 2017, 10(12), 1346; https://doi.org/10.3390/ma10121346

The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel

1
College of Engineering, Swansea University, Swansea SA1 8EN, UK
2
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK
3
Rolls-Royce plc, P.O. Box 31, Derby DE24 8BJ, UK
4
The Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights NSW 2234, Australia
*
Author to whom correspondence should be addressed.
Received: 12 September 2017 / Revised: 18 November 2017 / Accepted: 20 November 2017 / Published: 23 November 2017
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

Maraging steels gain many of their beneficial properties from heat treatments which induce the precipitation of intermetallic compounds. We consider here a two-stage heat-treatment, first involving austenitisation, followed by quenching to produce martensite and then an ageing treatment at a lower temperature to precipitation harden the martensite of a maraging steel. It is shown that with a suitable choice of the initial austenitisation temperature, the steel can be heat treated to produce enhanced toughness, strength and creep resistance. A combination of small angle neutron scattering, scanning electron microscopy, electron back-scattered diffraction, and atom probe tomography were used to relate the microstructural changes to mechanical properties. It is shown that such a combination of characterisation methods is necessary to quantify this complex alloy, and relate these microstructural changes to mechanical properties. It is concluded that a higher austenitisation temperature leads to a greater volume fraction of smaller Laves phase precipitates formed during ageing, which increase the strength and creep resistance but reduces toughness. View Full-Text
Keywords: small angle neutron scattering; maraging steel; precipitation strengthening; NiAl; Laves phase; atom probe tomography; creep; strength; ductile to brittle transition temperature small angle neutron scattering; maraging steel; precipitation strengthening; NiAl; Laves phase; atom probe tomography; creep; strength; ductile to brittle transition temperature
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Simm, T.H.; Sun, L.; Galvin, D.R.; Hill, P.; Rawson, M.; Birosca, S.; Gilbert, E.P.; Bhadeshia, H.; Perkins, K. The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel. Materials 2017, 10, 1346.

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