Microstructural hardness heterogeneity triggers fatigue crack non-propagation in as-hot-rolled Fe-30Mn-3Si-3Al twinning-induced plasticity steel

We investigated the fatigue properties and associated crack growth behaviors of as-hot-rolled and solution-treated Fe-30Mn-3Si-3Al twinning-induced plasticity (TWIP) steels. The as-hot-rolled TWIP steel showed a higher fatigue strength than that of the solution-treated steel. Moreover, the as-hot-rolled steel showed a non-propagating fatigue crack at the fatigue limit, while the solution-treated steel did not. The high resistance to fatigue crack growth cannot only be attributed to an increase in hardness, but is also associated with heterogeneous hardness distribution. The effect of hardness heterogeneity was numerically supported by Dugdale model-based simulations.