Microstructure and deformation behaviour of laser welded dissimilar dual phase steel joints

Abstract

The microstructure, microhardness, tensile properties, deformation and fracture behaviour of the Nd:YAG laser welded dissimilar joints between 780 and 980 MPa dual phase steels over a wide strain rate range were investigated. The welded joint shows hardening in fusion zone, supercritical and intercritical heat affected zones and softening in subcritical heat affected zones. For the dissimilar welded joint, the changing trend of the ductility is similar to those of the base metals with respect to the strain rate. The reason for the strain rate sensitivity of the failure location of the welded joint is that the major factor influencing the failure location changes from the content of ferrite to the content of ferrite/martensite interface with increasing strain rate.

Keywords:

• Laser welding
• Dual phase steel
• Dissimilar welded joint
• Microstructure
• Tensile properties
• Strain rate

Acknowledgement

This work was financially supported by the National Natural Science Foundation of China (grant no. 51101029). The authors would also like to thank the financial support from Specialized Research Fund for the Doctoral Program of Higher Education of China (grant no. 20110042120025), Fundamental Research Funds for the Central Universities of China (grant nos. N130405002 and N130410001) and the Natural Science Fund of Liaoning Province (grant no. 2014020034).