Abstract:
This paper presents a crystal plasticity model to predict the tensile response and crack
initiation in a mixed ferrite-martensite material with a low volume fraction of
pro-eutectoid ferrite, representative of a welding-induced inter-critical heat-affected
zone (IC-HAZ). It is shown that small volume fractions of ferrite can have a significant
effect on material strength and ductility depending on the ferrite grain orientation.
For relatively ‘soft’ ferrite grains, micro-cracks can grow across inter-ferrite ligaments
with damage accumulating in the ferrite, leading to a reduction in strength and
strain hardening, but with little influence on ductility; in contrast, relatively ‘hard’
ferrite grains act to accelerate micro-crack initiation, leading to reduced ductility,
with negligible influence on strain hardening up to the maximum load.
