Effect of elasto-plastic compatibility of grains on void-initiation criteria in low-carbon steel

The present study provides evidence for the role of ferrite-grain-size distributions on the occurrence of void initiation in a low-carbon steel. Various thermomechanical treatments were undertaken to create ultrafine, bimodal and coarse distributions of ferrite grain sizes. A two-parameter characterisation of probable void initiation sites is proposed, namely an elastic modulus difference and a difference in Schmid factor of the grains surrounding the void. All microstructures were categorised based on the ability to facilitate or resist void nucleation. For coarse grains, the elastic modulus and the Schmid factor differences are the highest, while they are intermediate for ultrafine grains and the lowest for the bimodal microstructure.