1 research outputs found
Residual ferrite in martensitic stainless steels: the effect of mechanical strength contrast on ductility
Ductile damage process of a martensitic stainless steel with 15vol% of residual ferrite and two populations of
carbide particles is investigated using a combined multiscale experimental and modelling approach. Whereas
Nb-rich carbides contribute to grain refinement, coarser Cr-rich carbides are preferential damage nucleation
sites. Three different heat treatments are applied to partially dissolve Cr-carbide particles while keeping the same
ratio of ferrite versus martensite volume fraction. Surprisingly, ductility decreases with decreasing volume fraction
of Cr-carbides. Nanoindentation mapping indicates that the strength contrast between ferrite and martensite
increases with carbide dissolution. According to finite element simulations of strain partitioning inside the two
phase microstructure, the stress triaxiality in ferrite increases with the mechanical strength contrast. This promotes
void nucleation and growth, reducing the fracture strain