Abstract
Maraging steels are precipitation strengthened martensitic steels with an unusual combination of strength and ductility. High Pressure Torsion (HPT) has been used in this study to produce maraging steel 250 grade (AMS 6512) with finer laths and higher dislocation density, both of which act as nucleation sites for precipitation, and reverted austenite formation. This study focusses on the effect of such a processing on the evolution of the microstructure, including kinetics of precipitation, recrystallisation and austenite reversion as well as the stability of the precipitates thus formed. It was found that the aging kinetics accelerated substantially in the HPT processed samples, by achieving peak aging conditions at considerably shorter temperature/time durations and also a peak hardness higher than the as-received sample by 41%. Detailed microstructural characterisation revealed a change in the precipitate morphology from spherical to plate like form in the overaged conditions. The impact of this on mechanical response of these steels was quantified using tensile tests. A 70% increase in ultimate tensile strength was achieved in HPT processed samples after peak aging. Changes in strength and ductility were correlated to the changes in the microstructure and their impending contributions to different strengthening mechanisms at play to enable better design of maraging steels.
Original language | English |
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Article number | 140665 |
Number of pages | 13 |
Journal | Materials Science and Engineering A |
Volume | 802.2021 |
Issue number | 20 January |
Early online date | 14 Dec 2020 |
DOIs | |
Publication status | Published - 20 Jan 2021 |
Bibliographical note
Publisher Copyright: © 2020 Elsevier B.V.Keywords
- High pressure torsion
- Maraging steels
- Mechanical behaviour
- Precipitation kinetics