TY - JOUR

T1 - High pressure torsion processing of maraging steel 250

T2 - Microstructure and mechanical behaviour evolution

AU - Jacob, Kevin

AU - Yadav, Deepesh

AU - Dixit, Saurabh

AU - Hohenwarter, Anton

AU - Jaya, Balila Nagamani

N1 - Publisher Copyright: © 2020 Elsevier B.V.

PY - 2021/1/20

Y1 - 2021/1/20

N2 - 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.

AB - 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.

KW - High pressure torsion

KW - Maraging steels

KW - Mechanical behaviour

KW - Precipitation kinetics

UR - http://www.scopus.com/inward/record.url?scp=85098195128&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2020.140665

DO - 10.1016/j.msea.2020.140665

M3 - Article

AN - SCOPUS:85098195128

VL - 802.2021

JO - Materials Science and Engineering A

JF - Materials Science and Engineering A

SN - 0921-5093

IS - 20 January

M1 - 140665

ER -