Anisotropy of strength and plasticity in lath martensite steel

Microtensile testing with a crystal plasticity analysis was employed using single block structured specimens to elucidate the anisotropic plasticity of lath martensite steel. Habit-plane-orientation-dependent yielding occurred in the single block specimens, as well as in the single packet specimens. This indicated that the plastic anisotropy arose from the substructure included in the block. The crystal plasticity analysis successfully reproduced the stress-strain behaviour of the single block and single packet structures by considering the dependency of the slip activity on the habit plane orientation. These calculations revealed that the restriction of the slip transfer at the block and sub-block boundaries slightly increased the flow stress, while the austenite retaining between the martensite laths might impact the slip activity, leading to the anisotropy of the strength and plasticity.