  The evolution of deformation from plasticity to localization to damage is
investigated in ferritic-pearlitic steel through nanometer-resolution
microstructure-correlated SEM-DIC strain mapping, enabled through highly
accurate microstructure-to-strain alignment. We reveal the key plasticity
mechanisms in ferrite and pearlite as well as their evolution into localization
and damage and their relation to the microstructural arrangement. Notably, two
contrasting mechanisms were identified that control whether damage initiation
in pearlite occurs and, through connection of localization hotspots in ferrite
grains, potentially results in macroscale fracture: (i) cracking of pearlite
bridges with relatively clean lamellar structure by brittle fracture of
cementite lamellae due to build-up of strain concentrations in nearby ferrite,
versus (ii) large plasticity without damage in pearlite bridges with a more
"open", chaotic pearlite morphology, which enables plastic percolation paths in
the interlamellar ferrite channels. Based on these insights, recommendations
for damage resistant ferritic-pearlitic steels are proposed.
