TY - JOUR

T1 - Predicting microstructure and strength of maraging steels

T2 - Elemental optimisation

AU - Galindo-Nava, E. I.

AU - Rainforth, W. M.

AU - Rivera-Díaz-del-Castillo, P. E.J.

PY - 2016/9/15

Y1 - 2016/9/15

N2 - 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 Ni3Ti, 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 Ni3Ti, 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.

AB - 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 Ni3Ti, 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 Ni3Ti, 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.

KW - Austenite

KW - Intermetallics

KW - Martensite

KW - Modelling

KW - Precipitation hardening

U2 - 10.1016/j.actamat.2016.07.020

DO - 10.1016/j.actamat.2016.07.020

M3 - Journal article

AN - SCOPUS:84978767528

VL - 117

SP - 270

EP - 285

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -