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Predicting microstructure and strength of maraging steels: Elemental optimisation

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Rainforth, WM 
Rivera-Díaz-del-Castillo, PEJ 

Abstract

A physics–based modelling framework to describe microstructure and mechanical properties in maraging steels is presented. It is based on prescribing the hierarchical structure of the martensitic matrix, including dislocation density, and lath and high–angle grain boundary spacing. The evolution of lath–shaped reverted austenite is described using grain–boundary diffusion laws within a lath unit. The dislocation density provides the preferential nucleation sites for precipitation, whereas descriptions for particle nucleation, growth and coarsening evolution are identified for Ni 3 Ti, NiAl and its variants, and BCC–Cu clusters. These results are combined to describe the hardness at different ageing temperatures in several [Formula presented], [Formula presented] and [Formula presented] steels. A critical assessment on individual contributions of typical alloying elements is performed. Ni and Mn control the kinetics of austenite formation, where the latter shows stronger influence on the growth kinetics. Ti additions induce higher hardness by precipitating stronger Ni 3 Ti, whereas Cu clusters induce low strength. A relationship between the reverted austenite and the total elongation in overaging conditions is also found. This result allows to identify optimal process and alloy design scenarios to improve the ductility whilst preserving high hardness in commercial maraging steels.

Description

Keywords

Martensite, Modelling, Precipitation hardening, Austenite, Intermetallics

Journal Title

Acta Materialia

Conference Name

Journal ISSN

1359-6454
1873-2453

Volume Title

117

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/L025213/1)