Fusion zone microstructure evolution of fiber laser welded press-hardened steels

Fusion zone microstructures of fiber laser welded Al-Si coated press-hardened steels at pre- and post-press hardened conditions were analyzed using transmission electron microscopy (TEM). TEM and nanoindentation studies suggest that dislocation-free -delta-ferrite phase formed in the weld metal (by ingress of the Al-Si surface coating into the fusion zone) exhibits lower nanohardness compared to a-ferrite transformed after press hardening. The nanoscale properties of delta-ferrite, alpha-ferrite, and martensite and their crystallographic orientation relationships are reported. (C) 2016 Elsevier Ltd. All rights reserved.